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There are no nephridia ("little kidneys") or other excretory organs in bryozoa, and it is thought that ammonia diffuses out through the body wall and lophophore. More complex waste products are not excreted but accumulate in the polypide, which degenerates after a few weeks. Some of the old polypide is recycled, but much of it remains as a large mass of dying cells containing accumulated wastes, and this is compressed into a "brown body". When the degeneration is complete, the cystid (outer part of the animal) produces a new polypide, and the brown body remains in the coelom, or in the stomach of the new polypide and is expelled next time the animal defecates.
Respiration and circulation
There are no respiratory organs, heart or blood vessels. Instead, zooids absorb oxygen and eliminate carbon dioxide through diffusion. Bryozoa accomplish diffusion through the use of either a thin membrane (in the case of anascans and some polyzoa) or through pseudopores located on the outer dermis of the zooid. The different bryozoan groups use various methods to share nutrients and oxygen between zooids: some have quite large gaps in the body walls, allowing the coelomic fluid to circulate freely; in others, the funiculi (internal "little ropes") of adjacent zooids connect via small pores in the body wall.
Reproduction and life cycles | Bryozoa | Wikipedia | 312 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Zooids of all phylactolaemate species are simultaneous hermaphrodites. Although those of many marine species are protandric, in other words function first as males and then as females, their colonies contain a combination of zooids that are in their male and female stages. In all species the ovaries develop on the inside of the body wall, and the testes on the funiculus connecting the stomach to the body wall. Eggs and sperm are released into the coelom, and sperm exit into the water through pores in the tips of some of the tentacles, and then are captured by the feeding currents of zooids that are producing eggs. Some species' eggs are fertilized externally after being released through a pore between two tentacles, which in some cases is at the tip of a small projection called the "intertentacular organ" in the base of a pair of tentacles. Others' are fertilized internally, in the intertentacular organ or in the coelom.
All phylactolaemates and stenolaemates, and most gymnolaemates, exhibit placentation, and has therefore lecithotrophic (non-feeding) larvae. Except for Cyclostomata and the small gymnolaemate family Epistomiidae, which are viviparous, all are brooders. Phylactolaemata brood their embryos in an internal brood sac, but Gymnolaemata both external membranous sacs, skeletal chambers (ovicells) and internal brooding sacs exist. The developing embryo relies on egg's yolk, extraembryonic nutrition (matrotrophy) or both.
In ctenostomes the mother provides a brood chamber for the fertilized eggs, and her polypide disintegrates, providing nourishment to the embryo. Stenolaemates produce specialized zooids to serve as brood chambers, and their eggs divide within this to produce up to 100 identical embryos. | Bryozoa | Wikipedia | 421 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Planktotrophic (feeding) larvae are only found in class Gymnolaemata: In the cheilostomatan suborder Malacostegina they are found in the two families Membraniporidae and Electridae, and in the three ctenostome families Alcyonidiidae, Farrellidae, and Hislopiidae. In addition there are a few unconfirmed records, like the solitary form Aethozoid where larvae has never been observed, but which is assumed to have planktotrophic larvae.
The cleavage of bryozoan eggs is biradial, in other words the early stages are bilaterally symmetrical. It is unknown how the coelom forms, since the metamorphosis from larva to adult destroys all of the larva's internal tissues. In many animals the blastopore, an opening in the surface of the early embryo, tunnels through to form the gut. However, in bryozoans the blastopore closes, and a new opening develops to create the mouth. | Bryozoa | Wikipedia | 215 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Bryozoan larvae vary in form, but all have a band of cilia round the body which enables them to swim, a tuft of cilia at the top, and an adhesive sac that everts and anchors them when they settle on a surface. Some gymnolaemate species produce cyphonautes larvae which have little yolk but a well-developed mouth and gut, and live as plankton for a considerable time before settling. These larvae have triangular shells of chitin, with one corner at the top and the base open, forming a hood round the downward-facing mouth. In 2006 it was reported that the cilia of cyphonautes larvae use the same range of techniques as those of adults to capture food. Species that brood their embryos form larvae that are nourished by large yolks, have no gut and do not feed, and such larvae quickly settle on a surface. In all marine species the larvae produce cocoons in which they metamorphose completely after settling: the larva's epidermis becomes the lining of the coelom, and the internal tissues are converted to a food reserve that nourishes the developing zooid until it is ready to feed. The larvae of phylactolaemates produce multiple polypides, so that each new colony starts with several zooids. In all species the founder zooids then grow the new colonies by budding clones of themselves. In phylactolaemates, zooids die after producing several clones, so that living zooids are found only round the edges of a colony. | Bryozoa | Wikipedia | 327 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Phylactolaemates can also reproduce asexually by a method that enables a colony's lineage to survive the variable and uncertain conditions of freshwater environments. Throughout summer and autumn they produce disc-shaped statoblasts, masses of cells that function as "survival pods" rather like the gemmules of sponges. Statoblasts form on the funiculus connected to the parent's gut, which nourishes them. As they grow, statoblasts develop protective bivalve-like shells made of chitin. When they mature, some statoblasts stick to the parent colony, some fall to the bottom ("sessoblasts"), some contain air spaces that enable them to float ("floatoblasts"), and some remain in the parent's cystid to re-build the colony if it dies. Statoblasts can remain dormant for considerable periods, and while dormant can survive harsh conditions such as freezing and desiccation. They can be transported across long distances by animals, floating vegetation, currents and winds, and even in the guts of larger animals. When conditions improve, the valves of the shell separate and the cells inside develop into a zooid that tries to form a new colony. Plumatella emarginata produces both "sessoblasts", which enable the lineage to control a good territory even if hard times decimate the parent colonies, and "floatoblasts", which spread to new sites. New colonies of Plumatella repens produce mainly "sessoblasts" while mature ones switch to "floatoblasts". A study estimated that one group of colonies in a patch measuring produced 800,000 statoblasts.
Cupuladriid Bryozoa are capable of both sexual and asexual reproduction. The sexually reproducing colonies (aclonal) are the result of a larval cupuladriid growing into an adult stage whereas the asexual colonies(clonal) are a result of a fragment of a colony of cupuladriids growing into its own colony. The different forms of reproduction in cupuladriids are achieved through a variety of methods depending on the morphology and classification of the zooid.
Ecology
Habitats and distribution
Most marine species live in tropical waters at depths less than . However, a few have been found in deep-sea trenches, especially around cold seeps, and others near the poles. | Bryozoa | Wikipedia | 508 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
The great majority of bryozoans are sessile. Typically, sessile bryozoans live on hard substrates including rocks, sand or shells. Boring bryozoans leave unique borehole traces after dissolving calcium carbonate substrates. Encrusting forms are much the commonest of these in shallow seas, but erect forms become more common as the depth increases. An example of incrustation on pebbles and cobbles is found in the diverse Pleistocene bryozoans found in northern Japan, where fossils have been found of single stones covered with more than 20 bryozoan species. Sediments with smaller particles, like sand or silt, are usually unsuitable habitat for bryozoans, but tiny colonies have been found encrusting grains of coarse sand. Some bryozoan species specialize in colonizing marine algae, seagrasses, and even mangrove roots; the genus Amphibiobeania lives on the leaves of mangrove trees and is called "amphibious" because it can survive regular exposure to air at low tide.
There are a variety of "free-living" bryozoans that live un-attached to a substrate. A few forms such as Cristatella can move. Lunulitiform cheilostomes are one group of free-living bryozoans with mobile colonies. They form small round colonies un-attached to any substrate; colonies of the genus Selenaria have been observed to "walk" around using setae. Another cheilostome family, the Cupuladriidae, convergently evolved similarly shaped colonies capable of movement. When observed in an aquarium, Selenaria maculata colonies were recorded to crawl at a speed of one meter per hour, climb over each other, move toward light, and right themselves when turned upside-down. Later study of this genus showed that neuroelectrical activity in the colonies increased in correlation with movement toward light sources. It is theorized that the capacity for movement arose as a side effect when colonies evolved longer setae for unburying themselves from sediment. | Bryozoa | Wikipedia | 420 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Other free-living bryozoans are moved freely by waves, currents, or other phenomena. An Antarctic species, Alcyonidium pelagosphaera, consists of floating colonies. The pelagic species is between in diameter, has the shape of a hollow sphere and consists of a single layer of autozooids. It is still not known if these colonies are pelagic their whole life or only represents a temporarily and previously undescribed juvenile stage. Colonies of the species Alcyonidium disciforme, which is disc-shaped and similarly free-living, inhabit muddy seabeds in the Arctic and can sequester sand grains they have engulfed, potentially using the sand as ballast to turn themselves right-side-up after they have been overturned. Some bryozoan species can form bryoliths, sphere-shaped free-living colonies that grow outward in all directions as they roll about on the seabed.
In 2014 it was reported that the bryozoan Fenestrulina rugula had become a dominant species in parts of Antarctica. Global warming has increased the rate of scouring by icebergs, and this species is particularly adept at recolonizing scoured areas.
The phylactolaemates live in all types of freshwater environment – lakes and ponds, rivers and streams, and estuaries – and are among the most abundant sessile freshwater animals. Some ctenostomes are exclusively freshwater while others prefer brackish water but can survive in freshwater. Scientists' knowledge of freshwater bryozoan populations in many parts of the world is incomplete, even in some parts of Europe. It was long thought that some freshwater species occurred worldwide, but since 2002 all of these have been split into more localized species. | Bryozoa | Wikipedia | 361 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Bryozoans grow in clonal colonies. A larval Bryozoan settles on a hard substance and produces a colony asexually through budding. These colonies can grow thousands of individual zooids in a relatively short period of time. Even though colonies of zooids grow through asexual reproduction, Bryozoans are hermaphrodites and new colonies can be formed through sexual reproduction and the generation of free swimming larvae. When colonies grow too large, however, they can split in two. This is the only case where asexual reproduction results in a new colony separate from its predecessor. Most colonies are stationary. Indeed, these colonies tend to be settled on immobile substances such as sediment and coarse substances. There are some colonies of freshwater species such as Cristatella mucedo that are able to move slowly on a creeping foot.
Interactions with non-human organisms
Marine species are common on coral reefs, but seldom a significant proportion of the total biomass. In temperate waters, the skeletons of dead colonies form a significant component of shell gravels, and live ones are abundant in these areas. The marine lace-like bryozoan Membranipora membranacea produces spines in response to predation by several species of sea slugs (nudibranchs). Other predators on marine bryozoans include fish, sea urchins, pycnogonids, crustaceans, mites and starfish. In general marine echinoderms and molluscs eat masses of zooids by gouging pieces of colonies, breaking their mineralized "houses", while most arthropod predators on bryozoans eat individual zooids.
In freshwater, bryozoans are among the most important filter feeders, along with sponges and mussels. Freshwater bryozoans are attacked by many predators, including snails, insects, and fish.
In Thailand the introduced species Pomacea canaliculata (golden apple snail), which is generally a destructive herbivore, has wiped out phylactolaemate populations wherever it has appeared. P. canaliculata also preys on a common freshwater gymnolaemate, but with less devastating effect. Indigenous snails do not feed on bryozoans. | Bryozoa | Wikipedia | 468 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Several species of the hydroid family Zancleidae have symbiotic relationships with bryozoans, some of which are beneficial to the hydroids while others are parasitic. Modifications appear in the shapes of some these hydroids, for example smaller tentacles or encrustation of the roots by bryozoans. The bryozoan Alcyonidium nodosum protects the whelk Burnupena papyracea against predation by the powerful and voracious rock lobster Jasus lalandii. While whelk shells encrusted by the bryozoans are stronger than those without this reinforcement, chemical defenses produced by the bryozoans are probably the more significant deterrent.
In the Banc d'Arguin offshore Mauritania the species Acanthodesia commensale, which is generally growing attached to gravel and hard-substrate, has formed a facultative symbiotic relationship with hermit crabs of the species Pseudopagurus cf. granulimanus resulting in egg-size structures known as bryoliths. Nucleating on an empty gastropod shell, the bryozoan colonies form multilamellar skeletal crusts that produce spherical encrustations and extend the living chamber of the hermit crab through helicospiral tubular growth.
Some phylactolaemate species are intermediate hosts for a group of myxozoa that have also been found to cause proliferative kidney disease, which is often fatal in salmonid fish, and has severely reduced wild fish populations in Europe and North America.
Membranipora membranacea, whose colonies feed and grow exceptionally fast in a wide range of current speeds, was first noticed in the Gulf of Maine in 1987 and quickly became the most abundant organism living on kelps. This invasion reduced the kelp population by breaking their fronds, so that its place as the dominant "vegetation" in some areas was taken by another invader, the large alga Codium fragile tomentosoides. These changes reduced the area of habitat available for local fish and invertebrates. M. membranacea has also invaded the northwest coast of the US. A few freshwater species have been also found thousands of kilometers from their native ranges. Some may have been transported naturally as statoblasts. Others more probably were spread by humans, for example on imported water plants or as stowaways on ships. | Bryozoa | Wikipedia | 502 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
Interaction with humans
Fish farms and hatcheries have lost stock to proliferative kidney disease, which is caused by one or more myxozoans that use bryozoans as alternate hosts.
Some fishermen in the North Sea have had to find other work because of a form of eczema (a skin disease) known as "Dogger Bank itch", caused by contact with bryozoans that have stuck to nets and lobster pots.
Marine bryozoans are often responsible for biofouling on ships' hulls, on docks and marinas, and on offshore structures. They are among the first colonizers of new or recently cleaned structures. Freshwater species are occasional nuisances in water pipes, drinking water purification equipment, sewage treatment facilities, and the cooling pipes of power stations.
A group of chemicals called bryostatins can be extracted from the marine bryozoan Bugula neritina. In 2001 pharmaceutical company GPC Biotech licensed bryostatin 1 from Arizona State University for commercial development as a treatment for cancer. GPC Biotech canceled development in 2003, saying that bryostatin 1 showed little effectiveness and some toxic side effects. In January 2008 a clinical trial was submitted to the United States National Institutes of Health to measure the safety and effectiveness of Bryostatin 1 in the treatment of Alzheimer's disease. However, no participants had been recruited by the end of December 2008, when the study was scheduled for completion. More recent work shows it has positive effects on cognition in patients with Alzheimer's disease with few side effects. About of bryozoans must be processed to extract of bryostatin, As a result, synthetic equivalents have been developed that are simpler to produce and apparently at least as effective. | Bryozoa | Wikipedia | 363 | 3416 | https://en.wikipedia.org/wiki/Bryozoa | Biology and health sciences | Lophotrochozoa | null |
The bay leaf is an aromatic leaf commonly used as a herb in cooking. It can be used whole, either dried or fresh, in which case it is removed from the dish before consumption, or less commonly used in ground form. The flavor that a bay leaf imparts to a dish has not been universally agreed upon, but many agree it is a subtle addition.
Bay leaves come from various plants and are used for their distinctive flavor and fragrance. The most common source is the bay laurel (Laurus nobilis). Other types include California bay laurel, Indian bay leaf, West Indian bay laurel, and Mexican bay laurel. Bay leaves contain essential oils, such as eucalyptol, terpenes, and methyleugenol, which contribute to their taste and aroma.
Bay leaves are used in cuisines including Indian, Filipino, European, and Caribbean. They are typically used in soups, stews, meat, seafood, and vegetable dishes. The leaves should be removed from the cooked food before eating as they can be abrasive in the digestive tract.
Bay leaves are used as an insect repellent in pantries and as an active ingredient in killing jars for entomology. In Eastern Orthodoxy liturgy, they are used to symbolize Jesus' destruction of Hades and freeing of the dead.
While some visually similar plants have poisonous leaves, bay leaves are not toxic. However, they remain stiff even after cooking and may pose a choking hazard or cause harm to the digestive tract if swallowed whole or in large pieces. Canadian food and drug regulations set specific standards for bay leaves, including limits on ash content, moisture levels, and essential oil content. | Bay leaf | Wikipedia | 336 | 3419 | https://en.wikipedia.org/wiki/Bay%20leaf | Biology and health sciences | Herbs and spices | Plants |
Sources
Bay leaves come from several plants, such as:
Bay laurel (Laurus nobilis, Lauraceae). Fresh or dried bay leaves are used in cooking for their distinctive flavour and fragrance. The leaves should be removed from the cooked food before eating (see safety section below). The leaves are often used to flavour soups, stews, braises and pâtés in many countries. The fresh leaves are very mild and do not develop their full flavour until several weeks after picking and drying.
California bay leaf. The leaf of the California bay tree (Umbellularia californica, Lauraceae), also known as California laurel, Oregon myrtle, and pepperwood, is similar to the Mediterranean bay laurel but contains the toxin umbellulone, which can cause methemoglobinemia.
Indian bay leaf or malabathrum (Cinnamomum tamala, Lauraceae) differs from bay laurel leaves, which are shorter and light- to medium-green in colour, with one large vein down the length of the leaf. Indian bay leaves are about twice as long and wider, usually olive green in colour, and have three veins running the length of the leaf. Culinarily, Indian bay leaves are quite different, having a fragrance and taste similar to cinnamon (cassia) bark, but milder.
Indonesian bay leaf or Indonesian laurel (salam leaf, Syzygium polyanthum, Myrtaceae) is not commonly found outside Indonesia; this herb is applied to meat and, less often, to rice and to vegetables.
West Indian bay leaf, the leaf of the West Indian bay tree (Pimenta racemosa, Myrtaceae) is used culinarily (especially in Caribbean cuisine) and to produce the cologne called bay rum.
Mexican bay leaf (Litsea glaucescens, Lauraceae).
Chemical constituents
The leaves of the European / Mediterranean plant Laurus nobilis contain about 1.3% essential oils (ol. lauri folii), consisting of 45% eucalyptol, 12% other terpenes, 8–12% terpinyl acetate, 3–4% sesquiterpenes, 3% methyleugenol, and other α- and β-pinenes, phellandrene, linalool, geraniol, terpineol, and also contain lauric acid. | Bay leaf | Wikipedia | 489 | 3419 | https://en.wikipedia.org/wiki/Bay%20leaf | Biology and health sciences | Herbs and spices | Plants |
Taste and aroma
If eaten whole, Laurus nobilis bay leaves are pungent and have a sharp, bitter taste. As with many spices and flavourings, the fragrance of the bay leaf is more noticeable than its taste. When the leaf is dried, the aroma is herbal, slightly floral, and somewhat similar to oregano and thyme. Myrcene, a component of many essential oils used in perfumery, can be extracted from this bay leaf. They also contain eugenol.
Uses
In Indian cuisine, bay laurel leaves are sometimes used in place of Indian bay leaf, although they have a different flavour. They are most often used in rice dishes like biryani and as an ingredient in garam masala. Bay leaves are called (, in Hindi), Tejpātā (তেজপাতা) in Bengali, তেজ পাত in Assamese and usually rendered into English as Tej Patta.
In the Philippines, dried bay laurel leaves are used in several Filipino dishes, such as menudo, beef pares, and adobo. Bay leaves were used for flavouring by the ancient Greeks. They are a fixture in the cooking of many European cuisines (particularly those of the Mediterranean), as well as in the Americas. They are used in soups, stews, brines, meat, seafood, vegetable dishes, and sauces. The leaves also flavour many classic French and Italian dishes. The leaves are most often used whole (sometimes in a ) and removed before serving (they can be abrasive in the digestive tract). Thai and Laotian cuisine employs bay leaf (, ) in a few Arab-influenced dishes, notably massaman curry.
Bay leaves can also be crushed or ground before cooking. Crushed bay leaves impart more fragrance than whole leaves, but are more difficult to remove and thus they are often used in a muslin bag or tea infuser. Ground bay laurel may be substituted for whole leaves and does not need to be removed, but it is much stronger.
To brew tea, bay leaves are best boiled for a brief period—typically 3 minutes—to prevent bitterness, as prolonged boiling may overpower the tea's flavor. Fresh bay leaves impart a stronger aroma, while dried leaves require longer steeping for a similar effect. | Bay leaf | Wikipedia | 471 | 3419 | https://en.wikipedia.org/wiki/Bay%20leaf | Biology and health sciences | Herbs and spices | Plants |
Bay leaves are also used in the making of jerk chicken in the Caribbean Islands. The bay leaves are soaked and placed on the cool side of the grill. Pimento sticks are placed on top of the leaves, and the chicken is placed on top and smoked. The leaves are also added whole to soups, stews, and other Caribbean dishes.
Bay leaves can also be used scattered in a pantry to repel meal moths, flies, and cockroaches. Mediouni-Ben Jemaa and Tersim 2011 find the essential oil to be usable as an insect repellent.
Bay leaves have been used in entomology as the active ingredient in killing jars. The crushed, fresh, young leaves are put into the jar under a layer of paper. The vapors they release kill insects slowly but effectively and keep the specimens relaxed and easy to mount. The leaves discourage the growth of molds. They are not effective for killing large beetles and similar specimens, but insects that have been killed in a cyanide killing jar can be transferred to a laurel jar to await mounting. There is confusion in the literature about whether Laurus nobilis is a source of cyanide to any practical extent, but there is no evidence that cyanide is relevant to its value in killing jars. It certainly is rich in various essential oil components that could incapacitate insects in high concentrations; such compounds include 1,8-cineole, alpha-terpinyl acetate, and methyl eugenol. It also is unclear to what extent the alleged effect of cyanide released by the crushed leaves has been mis-attributed to Laurus nobilis in confusion with the unrelated Prunus laurocerasus, the so-called cherry laurel, which certainly does contain dangerous concentrations of cyanogenic glycosides together with the enzymes to generate the hydrogen cyanide from the glycocides if the leaf is physically damaged.
Bay leaves are used in Eastern Orthodoxy liturgy. To mark Jesus' destruction of Hades and freeing of the dead, parishioners throw bay leaves and flowers into the air, letting them flutter to the ground. | Bay leaf | Wikipedia | 434 | 3419 | https://en.wikipedia.org/wiki/Bay%20leaf | Biology and health sciences | Herbs and spices | Plants |
Safety
Some members of the laurel family, as well as the unrelated but visually similar mountain laurel and cherry laurel, have leaves that are poisonous to humans and livestock. While these plants are not sold anywhere for culinary use, their visual similarity to bay leaves has led to the oft-repeated belief that bay leaves should be removed from food after cooking because they are poisonous. This is not true; bay leaves may be eaten without toxic effect. However, they remain unpleasantly stiff even after thorough cooking, and if swallowed whole or in large pieces they may pose a risk of harming the digestive tract or causing choking. Thus, most recipes that use bay leaves will recommend their removal after the cooking process has finished.
Canadian food and drug regulations
The Canadian government requires that ground bay leaves contain no more than 4.5% total ash material, with a maximum of 0.5% of which is insoluble in hydrochloric acid. To be considered dried, they must contain 7% moisture or less. The oil content cannot be less than 1 milliliter per 100 grams of the spice. | Bay leaf | Wikipedia | 221 | 3419 | https://en.wikipedia.org/wiki/Bay%20leaf | Biology and health sciences | Herbs and spices | Plants |
A bulletin board system (BBS), also called a computer bulletin board service (CBBS), is a computer server running software that allows users to connect to the system using a terminal program. Once logged in, the user performs functions such as uploading and downloading software and data, reading news and bulletins, and exchanging messages with other users through public message boards and sometimes via direct chatting. In the early 1980s, message networks such as FidoNet were developed to provide services such as NetMail, which is similar to internet-based email.
Many BBSes also offered online games in which users could compete with each other. BBSes with multiple phone lines often provided chat rooms, allowing users to interact with each other. Bulletin board systems were in many ways a precursor to the modern form of the World Wide Web, social networks, and other aspects of the Internet. Low-cost, high-performance asynchronous modems drove the use of online services and BBSes through the early 1990s. InfoWorld estimated that there were 60,000 BBSes serving 17 million users in the United States alone in 1994, a collective market much larger than major online services such as CompuServe.
The introduction of inexpensive dial-up internet service and the Mosaic web browser offered ease of use and global access that BBS and online systems did not provide, and led to a rapid crash in the market starting in late 1994 to early 1995. Over the next year, many of the leading BBS software providers went bankrupt and tens of thousands of BBSes disappeared. Today, BBSing survives largely as a nostalgic hobby in most parts of the world, but it is still a popular form of communication for middle aged Taiwanese (see PTT Bulletin Board System). Most surviving BBSes are accessible over Telnet and typically offer free email accounts, FTP services, and IRC. Some offer access through packet switched networks or packet radio connections.
History
Precursors
A precursor to the public bulletin board system was Community Memory, which started in August 1973 in Berkeley, California. Microcomputers did not exist at that time, and modems were both expensive and slow. Community Memory ran on a mainframe computer and was accessed through terminals located in several San Francisco Bay Area neighborhoods. The poor quality of the original modem connecting the terminals to the mainframe prompted Community Memory hardware person, Lee Felsenstein, to invent the Pennywhistle modem, whose design was influential in the mid-1970s. | Bulletin board system | Wikipedia | 506 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
Community Memory allowed the user to type messages into a computer terminal after inserting a coin, and offered a "pure" bulletin board experience with public messages only (no email or other features). It did offer the ability to tag messages with keywords, which the user could use in searches. The system acted primarily in the form of a buy and sell system with the tags taking the place of the more traditional classifications. But users found ways to express themselves outside these bounds, and the system spontaneously created stories, poetry and other forms of communications. The system was expensive to operate, and when their host machine became unavailable and a new one could not be found, the system closed in January 1975.
Similar functionality was available to most mainframe users, which might be considered a sort of ultra-local BBS when used in this fashion. Commercial systems, expressly intended to offer these features to the public, became available in the late 1970s and formed the online service market that lasted into the 1990s. One particularly influential example was PLATO, which had thousands of users by the late 1970s, many of whom used the messaging and chat room features of the system in the same way that would later become common on BBSes.
The first BBSes
Early modems were generally either expensive or very simple devices using acoustic couplers to handle telephone operation. The user would pick up the phone, dial a number, then press the handset into rubber cups on the top of the modem. Disconnecting at the end of a call required the user to pick up the handset and return it to the phone. Examples of direct-connecting modems did exist, and these often allowed the host computer to send it commands to answer or hang up calls, but these were very expensive devices used by large banks and similar companies.
With the introduction of microcomputers with expansion slots, like the S-100 bus machines and Apple II, it became possible for the modem to communicate instructions and data on separate lines. These machines typically only supported asynchronous communications, and synchronous modems were much more expensive than asynchronous modems. A number of modems of this sort were available by the late 1970s. This made the BBS possible for the first time, as it allowed software on the computer to pick up an incoming call, communicate with the user, and then hang up the call when the user logged off. | Bulletin board system | Wikipedia | 489 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
The first public dial-up BBS was developed by Ward Christensen and Randy Suess, members of the Chicago Area Computer Hobbyists' Exchange (CACHE). According to an early interview, when Chicago was snowed under during the Great Blizzard of 1978, the two began preliminary work on the Computerized Bulletin Board System, or CBBS. The system came into existence largely through a fortuitous combination of Christensen having a spare S-100 bus computer and an early Hayes internal modem, and Suess's insistence that the machine be placed at his house in Chicago where it would be a local phone call for more users. Christensen patterned the system after the cork board his local computer club used to post information like "need a ride". CBBS officially went online on 16 February 1978. CBBS, which kept a count of callers, reportedly connected 253,301 callers before it was finally retired.
Smartmodem
A key innovation required for the popularization of the BBS was the Smartmodem manufactured by Hayes Microcomputer Products. Internal modems like the ones used by CBBS and similar early systems were usable, but generally expensive due to the manufacturer having to make a different modem for every computer platform they wanted to target. They were also limited to those computers with internal expansion, and could not be used with other useful platforms like video terminals. External modems were available for these platforms but required the phone to be dialed using a conventional handset. Internal modems could be software-controlled to perform outbound and inbound calls, but external modems had only the data pins to communicate with the host system.
Hayes' solution to the problem was to use a small microcontroller to implement a system that examined the data flowing into the modem from the host computer, watching for certain command strings. This allowed commands to be sent to and from the modem using the same data pins as all the rest of the data, meaning it would work on any system that could support even the most basic modems. The Smartmodem could pick up the phone, dial numbers, and hang up again, all without any operator intervention. The Smartmodem was not necessary for BBS use but made overall operation dramatically simpler. It also improved usability for the caller, as most terminal software allowed different phone numbers to be stored and dialed on command, allowing the user to easily connect to a series of systems. | Bulletin board system | Wikipedia | 494 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
The introduction of the Smartmodem led to the first real wave of BBS systems. Limited in speed and storage capacity, these systems were normally dedicated solely to messaging, private email and public forums. File transfers were extremely slow at these speeds, and file libraries were typically limited to text files containing lists of other BBS systems. These systems attracted a particular type of user who used the BBS as a unique type of communications medium, and when these local systems were crowded from the market in the 1990s, their loss was lamented for many years.
Higher speeds, commercialization
Speed improved with the introduction of 1200 bit/s asynchronous modems in the early 1980s, giving way to 2400 bit/s fairly rapidly. The improved performance led to a substantial increase in BBS popularity. Most of the information was displayed using ordinary ASCII text or ANSI art, but a number of systems attempted character-based graphical user interfaces (GUIs) which began to be practical at 2400 bit/s.
There was a lengthy delay before 9600 bit/s models began to appear on the market. 9600 bit/s was not even established as a strong standard before V.32bis at 14.4 kbit/s took over in the early 1990s. This period also saw the rapid rise in capacity and a dramatic drop in the price of hard drives. By the late 1980s, many BBS systems had significant file libraries, and this gave rise to leechingusers calling BBSes solely for their files. These users would use the modem for some time, leaving less time for other users, who got busy signals. The resulting upheaval eliminated many of the pioneering message-centric systems. | Bulletin board system | Wikipedia | 349 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
This also gave rise to a new class of BBS systems, dedicated solely to file upload and downloads. These systems charged for access, typically a flat monthly fee, compared to the per-hour fees charged by Event Horizons BBS and most online services. Many third-party services were developed to support these systems, offering simple credit card merchant account gateways for the payment of monthly fees, and entire file libraries on compact disk that made initial setup very easy. Early 1990s editions of Boardwatch were filled with ads for single-click install solutions dedicated to these new sysops. While this gave the market a bad reputation, it also led to its greatest success. During the early 1990s, there were a number of mid-sized software companies dedicated to BBS software, and the number of BBSes in service reached its peak.
Towards the early 1990s, BBS became so popular that it spawned three monthly magazines, Boardwatch, BBS Magazine, and in Asia and Australia, Chips 'n Bits Magazine which devoted extensive coverage of the software and technology innovations and people behind them, and listings to US and worldwide BBSes. In addition, in the US, a major monthly magazine, Computer Shopper, carried a list of BBSes along with a brief abstract of each of their offerings.
GUIs
Through the late 1980s and early 1990s, there was considerable experimentation with ways to develop user-friendly interfaces for BBSes. Almost every popular system used ANSI-based color menus to make reading easier on capable hardware and terminal emulators, and most also allowed cursor commands to offer command-line recall and similar features. Another common feature was the use of autocomplete to make menu navigation simpler, a feature that would not re-appear on the Web until decades later. | Bulletin board system | Wikipedia | 360 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
A number of systems also made forays into GUI-based interfaces, either using character graphics sent from the host, or using custom GUI-based terminal systems. The latter initially appeared on the Macintosh platform, where TeleFinder and FirstClass became very popular. FirstClass offered a host of features that would be difficult or impossible under a terminal-based solution, including bi-directional information flow and non-blocking operation that allowed the user to exchange files in both directions while continuing to use the message system and chat, all in separate windows. Will Price's "Hermes", released in 1988, combined a familiar PC style with Macintosh GUI interface. (Hermes was already "venerable" by 1994 although the Hermes II release remained popular.) Skypix featured on Amiga a complete markup language. It used a standardized set of icons to indicate mouse driven commands available online and to recognize different filetypes present on BBS storage media. It was capable of transmitting data like images, audio files, and audio clips between users linked to the same BBS or off-line if the BBS was in the circuit of the FidoNet organization.
On the PC, efforts were more oriented to extensions of the original terminal concept, with the GUI being described in the information on the host. One example was the Remote Imaging Protocol, essentially a picture description system, which remained relatively obscure. Probably the ultimate development of this style of operation was the dynamic page implementation of the University of Southern California BBS (USCBBS) by Susan Biddlecomb, which predated the implementation of the HTML Dynamic web page. A complete Dynamic web page implementation was accomplished using TBBS with a TDBS add-on presenting a complete menu system individually customized for each user.
Rise of the Internet and decline of BBS
The demand for complex ANSI and ASCII screens and larger file transfers taxed available channel capacity, which in turn increased demand for faster modems. 14.4 kbit/s modems were standard for a number of years while various companies attempted to introduce non-standard systems with higher performancenormally about 19.2 kbit/s. Another delay followed due to a long V.34 standards process before 28.8 kbit/s was released, only to be quickly replaced by 33.6 kbit/s, and then 56 kbit/s. | Bulletin board system | Wikipedia | 478 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
These increasing speeds had the side effect of dramatically reducing the noticeable effects of channel efficiency. When modems were slow, considerable effort was put into developing the most efficient protocols and display systems possible. TCP/IP ran slowly over 1200 bit/s modems. 56 kbit/s modems could access the protocol suite more quickly than with slower modems. Dial-up Internet service became widely available in the mid-1990s to the general public outside of universities and research laboratories, and connectivity was included in most general-use operating systems by default as Internet access became popular.
These developments together resulted in the sudden obsolescence of bulletin board technology in 1995 and the collapse of its supporting market. Technically, Internet service offered an enormous advantage over BBS systems, as a single connection to the user's Internet service provider allowed them to contact services around the world. In comparison, BBS systems relied on a direct point-to-point connection, so even dialing multiple local systems required multiple phone calls. Internet protocols also allowed a single connection to be used to contact multiple services simultaneously; for example, downloading files from an FTP library while checking the weather on a local news website. Even with a shell account, it was possible to multitask using job control or a terminal multiplexer such as GNU Screen. In comparison, a connection to a BBS allowed access only to the information on that system.
Estimating numbers
According to the FidoNet Nodelist, BBSes reached their peak usage around 1996, which was the same period that the World Wide Web and AOL became mainstream. BBSes rapidly declined in popularity thereafter, and were replaced by systems using the Internet for connectivity. Some of the larger commercial BBSes, such as MaxMegabyte and ExecPC BBS, evolved into Internet service providers.
The website textfiles.com serves as an archive that documents the history of the BBS. The historical BBS list on textfiles.com contains over 105,000 BBSes that have existed over a span of 20 years in North America alone. The owner of textfiles.com, Jason Scott, also produced BBS: The Documentary, a DVD film that chronicles the history of the BBS and features interviews with well-known people (mostly from the United States) from the heyday BBS era. | Bulletin board system | Wikipedia | 475 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
In the 2000s, most traditional BBS systems migrated to the Internet using Telnet or SSH protocols. As of September 2022, between 900 and 1000 are thought to be active via the Internet fewer than 30 of these being of the traditional "dial-up" (modem) variety.
Software and hardware
Unlike modern websites and online services that are typically hosted by third-party companies in commercial data centers, BBS computers (especially for smaller boards) were typically operated from the system operator's home. As such, access could be unreliable, and in many cases, only one user could be on the system at a time. Only larger BBSes with multiple phone lines using specialized hardware, multitasking software, or a LAN connecting multiple computers, could host multiple simultaneous users.
The first BBSes each used their own unique software, quite often written entirely or at least customized by the system operators themselves, running on early S-100 bus microcomputer systems such as the Altair 8800, IMSAI 8080 and Cromemco under the CP/M operating system. Soon after, BBS software was being written for all of the major home computer systems of the late 1970s erathe Apple II, Atari 8-bit computers, Commodore PET, TI-99/4A, and TRS-80 being some of the most popular.
In 1981, the IBM Personal Computer was introduced and MS-DOS soon became the operating system on which the majority of BBS programs were run. RBBS-PC, ported over from the CP/M world, and Fido BBS, developed by Tom Jennings (who later founded FidoNet) were the first notable MS-DOS BBS programs. Many successful commercial BBS programs were developed, such as PCBoard BBS, RemoteAccess BBS, Magpie and Wildcat! BBS. Popular freeware BBS programs included Telegard BBS and Renegade BBS, which both had early origins from leaked WWIV BBS source code. | Bulletin board system | Wikipedia | 408 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
BBS systems on other systems remained popular, especially home computers, largely because they catered to the audience of users running those machines. The ubiquitous Commodore 64 (introduced in 1982) was a common platform in the 1980s. Popular commercial BBS programs were Blue Board, Ivory BBS, Color64 and CNet 64. There was also a devoted contingent of BBS users on TI-99/4A computers, long after Texas Instruments had discontinued the computer in the aftermath of their price war with Commodore. Popular BBSes for the TI-99/4A included Techie, TIBBS (Texas Instruments Bulletin Board System), TI-COMM, and Zyolog. In the early 1990s, a small number of BBSes were also running on the Commodore Amiga. Popular BBS software for the Amiga were ABBS, Amiexpress, C-Net, StormforceBBS, Infinity and Tempest. There was also a small faction of devoted Atari BBSes that used the Atari 800, then the 800XL, and eventually the 1040ST. The earlier machines generally lacked hard drive capabilities, which limited them primarily to messaging.
MS-DOS continued to be the most popular operating system for BBS use up until the mid-1990s, and in the early years, most multi-node BBSes were running under a DOS based multitasker such as DESQview or consisted of multiple computers connected via a LAN. In the late 1980s, a handful of BBS developers implemented multitasking communications routines inside their software, allowing multiple phone lines and users to connect to the same BBS computer. These included Galacticomm's MajorBBS (later WorldGroup), eSoft The Bread Board System (TBBS), and Falken. Other popular BBS's were Maximus and Opus, with some associated applications such as BinkleyTerm being based on characters from the Berkley Breathed cartoon strip of Bloom County. Though most BBS software had been written in BASIC or Pascal (with some low-level routines written in assembly language), the C language was starting to gain popularity. | Bulletin board system | Wikipedia | 422 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
By 1995, many of the DOS-based BBSes had begun switching to modern multitasking operating systems, such as OS/2, Windows 95, and Linux. One of the first graphics-based BBS applications was Excalibur BBS with low-bandwidth applications that required its own client for efficiency. This led to one of the earliest implementations of Electronic Commerce in 1996 with replication of partner stores around the globe. TCP/IP networking allowed most of the remaining BBSes to evolve and include Internet hosting capabilities. Recent BBS software, such as Synchronet, Mystic BBS, EleBBS, DOC, Magpie or Wildcat! BBS, provide access using the Telnet protocol rather than dialup, or by using legacy DOS-based BBS software with a FOSSIL-to-Telnet redirector such as NetFoss.
Presentation
BBSes were generally text-based, rather than GUI-based, and early BBSes conversed using the simple ASCII character set. However, some home computer manufacturers extended the ASCII character set to take advantage of the advanced color and graphics capabilities of their systems. BBS software authors included these extended character sets in their software, and terminal program authors included the ability to display them when a compatible system was called. Atari's native character set was known as ATASCII, while most Commodore BBSes supported PETSCII. PETSCII was also supported by the nationwide online service Quantum Link.
The use of these custom character sets was generally incompatible between manufacturers. Unless a caller was using terminal emulation software written for, and running on, the same type of system as the BBS, the session would simply fall back to simple ASCII output. For example, a Commodore 64 user calling an Atari BBS would use ASCII rather than the native character set of either. As time progressed, most terminal programs began using the ASCII standard, but could use their native character set if it was available. | Bulletin board system | Wikipedia | 405 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
COCONET, a BBS system made by Coconut Computing, Inc., was released in 1988 and only supported a GUI (no text interface was initially available but eventually became available around 1990), and worked in EGA/VGA graphics mode, which made it stand out from text-based BBS systems. COCONET's bitmap and vector graphics and support for multiple type fonts were inspired by the PLATO system, and the graphics capabilities were based on what was available in the Borland Graphics Interface library. A competing approach called Remote Imaging Protocol (RIP) emerged and was promoted by Telegrafix in the early to mid-1990s but it never became widespread. A teletext technology called NAPLPS was also considered, and although it became the underlying graphics technology behind the Prodigy service, it never gained popularity in the BBS market. There were several GUI-based BBSes on the Apple Macintosh platform, including TeleFinder and FirstClass, but these were mostly confined to the Mac market.
In the UK, the BBC Micro based OBBS software, available from Pace for use with their modems, optionally allowed for color and graphics using the Teletext based graphics mode available on that platform. Other systems used the Viewdata protocols made popular in the UK by British Telecom's Prestel service, and the on-line magazine Micronet 800 whom were busy giving away modems with their subscriptions.
Over time, terminal manufacturers started to support ANSI X3.64 in addition to or instead of proprietary terminal control codes, e.g., color, cursor positioning.
The most popular form of online graphics was ANSI art, which combined the IBM Extended ASCII character set's blocks and symbols with ANSI escape sequences to allow changing colors on demand, provide cursor control and screen formatting, and even basic musical tones. During the late 1980s and early 1990s, most BBSes used ANSI to make elaborate welcome screens, and colorized menus, and thus, ANSI support was a sought-after feature in terminal client programs. The development of ANSI art became so popular that it spawned an entire BBS "artscene" subculture devoted to it.
The Amiga Skyline BBS software in 1988 featured a script markup language communication protocol called Skypix which was capable of giving the user a complete graphical interface, featuring rich graphics, changeable fonts, mouse-controlled actions, animations and sound. | Bulletin board system | Wikipedia | 504 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
Today, most BBS software that is still actively supported, such as Worldgroup, Wildcat! BBS and Citadel/UX, is Web-enabled, and the traditional text interface has been replaced (or operates concurrently) with a Web-based user interface. For those more nostalgic for the true BBS experience, one can use NetSerial (Windows) or DOSBox (Windows/*nix) to redirect DOS COM port software to telnet, allowing them to connect to Telnet BBSes using 1980s and 1990s era modem terminal emulation software, like Telix, Terminate, Qmodem and Procomm Plus. Modern 32-bit terminal emulators such as mTelnet and SyncTerm include native telnet support.
Content and access
Since most early BBSes were run by computer hobbyists, content was largely technical, with user communities revolving around hardware and software discussions.
As the BBS phenomenon grew, so did the popularity of special interest boards. Bulletin Board Systems could be found for almost every hobby and interest. Popular interests included politics, religion, music, dating, and alternative lifestyles. Many system operators also adopted a theme in which they customized their entire BBS (welcome screens, prompts, menus, and so on) to reflect that theme. Common themes were based on fantasy, or were intended to give the user the illusion of being somewhere else, such as in a sanatorium, wizard's castle, or on a pirate ship.
In the early days, the file download library consisted of files that the system operators obtained themselves from other BBSes and friends. Many BBSes inspected every file uploaded to their public file download library to ensure that the material did not violate copyright law. As time went on, shareware CD-ROMs were sold with up to thousands of files on each CD-ROM. Small BBSes copied each file individually to their hard drive. Some systems used a CD-ROM drive to make the files available. Advanced BBSes used Multiple CD-ROM disc changer units that switched 6 CD-ROM disks on demand for the caller(s). Large systems used all 26 DOS drive letters with multi-disk changers housing tens of thousands of copyright-free shareware or freeware files available to all callers. These BBSes were generally more family-friendly, avoiding the seedier side of BBSes. Access to these systems varied from single to multiple modem lines with some requiring little or no confirmed registration. | Bulletin board system | Wikipedia | 508 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
Some BBSes, called elite, WaReZ, or pirate boards, were exclusively used for distributing cracked software, phreaking materials, and other questionable or unlawful content. These BBSes often had multiple modems and phone lines, allowing several users to upload and download files at once. Most elite BBSes used some form of new user verification, where new users would have to apply for membership and attempt to prove that they were not a law enforcement officer or a lamer. The largest elite boards accepted users by invitation only. Elite boards also spawned their own subculture and gave rise to the slang known today as leetspeak.
Another common type of board was the support BBS run by a manufacturer of computer products or software. These boards were dedicated to supporting users of the company's products with question and answer forums, news and updates, and downloads. Most of them were not a free call. Today, these services have moved to the Web.
Some general-purpose Bulletin Board Systems had special levels of access that were given to those who paid extra money, uploaded useful files or knew the system operator personally. These specialty and pay BBSes usually had something unique to offer their users, such as large file libraries, warez, pornography, chat rooms or Internet access.
Pay BBSes such as The WELL and Echo NYC (now Internet forums rather than dial-up), ExecPC, PsudNetwork and MindVox (which folded in 1996) were admired for their close, friendly communities and quality discussion forums. However, many free BBSes also maintained close communities, and some even had annual or bi-annual events where users would travel great distances to meet face-to-face with their on-line friends. These events were especially popular with BBSes that offered chat rooms.
Some of the BBSes that provided access to illegal content faced opposition. On July 12, 1985, in conjunction with a credit card fraud investigation, the Middlesex County, New Jersey Sheriff's department raided and seized The Private Sector BBS, which was the official BBS for grey hat hacker quarterly 2600 Magazine at the time. The notorious Rusty n Edie's BBS, in Boardman, Ohio, was raided by the FBI in January 1993 for trading unlicensed software, and later sued by Playboy for copyright infringement in November 1997. In Flint, Michigan, a 21-year-old man was charged with distributing child pornography through his BBS in March 1996.
Networks | Bulletin board system | Wikipedia | 500 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
Most early BBSes operated as individual systems. Information contained on that BBS never left the system, and users would only interact with the information and user community on that BBS alone. However, as BBSes became more widespread, there evolved a desire to connect systems together to share messages and files with distant systems and users. The largest such network was FidoNet.
As is it was prohibitively expensive for the hobbyist system operator to have a dedicated connection to another system, FidoNet was developed as a store and forward network. Private email (Netmail), public message boards (Echomail) and eventually even file attachments on a FidoNet-capable BBS would be bundled into one or more archive files over a set time interval. These archive files were then compressed with ARC or ZIP and forwarded to (or polled by) another nearby node or hub via a dialup Xmodem session. Messages would be relayed around various FidoNet hubs until they were eventually delivered to their destination. The hierarchy of FidoNet BBS nodes, hubs, and zones was maintained in a routing table called a Nodelist. Some larger BBSes or regional FidoNet hubs would make several transfers per day, some even to multiple nodes or hubs, and as such, transfers usually occurred at night or in the early morning when toll rates were lowest. In Fido's heyday, sending a Netmail message to a user on a distant FidoNet node, or participating in an Echomail discussion could take days, especially if any FidoNet nodes or hubs in the message's route only made one transfer call per day. | Bulletin board system | Wikipedia | 339 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
FidoNet was platform-independent and would work with any BBS that was written to use it. BBSes that did not have integrated FidoNet capability could usually add it using an external FidoNet front-end mailer such as SEAdog, FrontDoor, BinkleyTerm, InterMail or D'Bridge, and a mail processor such as FastEcho or Squish. The front-end mailer would conduct the periodic FidoNet transfers, while the mail processor would usually run just before and just after the mailer ran. This program would scan for and pack up new outgoing messages, and then unpack, sort and "toss" the incoming messages into a BBS user's local email box or into the BBS's local message bases reserved for Echomail. As such, these mail processors were commonly called "scanner/tosser/packers".
Many other BBS networks followed the example of FidoNet, using the same standards and the same software. These were called FidoNet Technology Networks (FTNs). They were usually smaller and targeted at selected audiences. Some networks used QWK doors, and others such as RelayNet (RIME) and WWIVnet used non-Fido software and standards.
Before commercial Internet access became common, these networks of BBSes provided regional and international e-mail and message bases. Some even provided gateways, such as UFGATE, by which members could send and receive e-mail to and from the Internet via UUCP, and many FidoNet discussion groups were shared via gateway to Usenet. Elaborate schemes allowed users to download binary files, search gopherspace, and interact with distant programs, all using plain-text e-mail.
As the volume of FidoNet Mail increased and newsgroups from the early days of the Internet became available, satellite data downstream services became viable for larger systems. The satellite service provided access to FidoNet and Usenet newsgroups in large volumes at a reasonable fee. By connecting a small dish and receiver, a constant downstream of thousands of FidoNet and Usenet newsgroups could be received. The local BBS only needed to upload new outgoing messages via the modem network back to the satellite service. This method drastically reduced phone data transfers while dramatically increasing the number of message forums. | Bulletin board system | Wikipedia | 478 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
FidoNet is still in use today, though in a much smaller form, and many Echomail groups are still shared with Usenet via FidoNet to Usenet gateways. Widespread abuse of Usenet with spam and pornography has led to many of these FidoNet gateways to cease operation completely.
Shareware and freeware
Much of the shareware movement was started via user distribution of software through BBSes. A notable example was Phil Katz's PKARC (and later PKZIP, using the same ".zip" algorithm that WinZip and other popular archivers now use); also other concepts of software distribution like freeware, postcardware like JPEGview and donationware like Red Ryder for the Macintosh first appeared on BBS sites. Doom from id Software and nearly all Apogee Software games were distributed as shareware. The Internet has largely erased the distinction of sharewaremost users now download the software directly from the developer's website rather than receiving it from another BBS user "sharing" it. Today, shareware often refers to electronically distributed software from a small developer.
Many commercial BBS software companies that continue to support their old BBS software products switched to the shareware model or made it entirely free. Some companies were able to make the move to the Internet and provide commercial products with BBS capabilities.
Features
A classic BBS had:
A computer
One or more modems
One or more phone lines, with more allowing for increased concurrent users
A BBS software package
A sysop – system operator
A user community | Bulletin board system | Wikipedia | 317 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
The BBS software usually provides:
Menu systems
One or more message bases
Uploading and downloading of message packets in QWK format using XMODEM, YMODEM or ZMODEM
File areas
Live viewing of all caller activity by the system operator
Voting – opinion booths
Statistics on message posters, top uploaders / downloaders
Online games (usually single player or only a single active player at a given time)
A doorway to third-party online games
Usage auditing capabilities
Multi-user chat (only possible on multi-line BBSes)
Internet email (more common in later Internet-connected BBSes)
Networked message boards
Most modern BBSes allow telnet access over the Internet using a telnet server and a virtual FOSSIL driver.
A "yell for SysOp" page caller side menu item that sounded an audible alarm to the system operator. If chosen, the system operator could then initiate a text-to-text chat with the caller.
Primitive social networking features, such as leaving messages on a user's profile | Bulletin board system | Wikipedia | 208 | 3430 | https://en.wikipedia.org/wiki/Bulletin%20board%20system | Technology | Internet | null |
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for special senses such as vision, hearing and olfaction. Being the most specialized organ, it is responsible for receiving information from the sensory nervous system, processing those information (thought, cognition, and intelligence) and the coordination of motor control (muscle activity and endocrine system).
While invertebrate brains arise from paired segmental ganglia (each of which is only responsible for the respective body segment) of the ventral nerve cord, vertebrate brains develop axially from the midline dorsal nerve cord as a vesicular enlargement at the rostral end of the neural tube, with centralized control over all body segments. All vertebrate brains can be embryonically divided into three parts: the forebrain (prosencephalon, subdivided into telencephalon and diencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon, subdivided into metencephalon and myelencephalon). The spinal cord, which directly interacts with somatic functions below the head, can be considered a caudal extension of the myelencephalon enclosed inside the vertebral column. Together, the brain and spinal cord constitute the central nervous system in all vertebrates.
In humans, the cerebral cortex contains approximately 14–16 billion neurons, and the estimated number of neurons in the cerebellum is 55–70 billion. Each neuron is connected by synapses to several thousand other neurons, typically communicating with one another via cytoplasmic processes known as dendrites and axons. Axons are usually myelinated and carry trains of rapid micro-electric signal pulses called action potentials to target specific recipient cells in other areas of the brain or distant parts of the body. The prefrontal cortex, which controls executive functions, is particularly well developed in humans. | Brain | Wikipedia | 435 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Physiologically, brains exert centralized control over a body's other organs. They act on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.
The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from a digital computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways.
This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important that are covered in the human brain article are brain disease and the effects of brain damage.
Structure
The shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from invertebrates. | Brain | Wikipedia | 358 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.
Cellular structure | Brain | Wikipedia | 161 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The brains of all species are composed primarily of two broad classes of brain cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. In humans, the cerebral cortex contains approximately 14–16 billion neurons, and the estimated number of neurons in the cerebellum is 55–70 billion. Each neuron is connected by synapses to several thousand other neurons. The property that makes neurons unique is their ability to send signals to specific target cells, sometimes over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.
Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell. | Brain | Wikipedia | 445 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.
Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.
Evolution
Generic bilaterian nervous system | Brain | Wikipedia | 297 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Except for a few primitive organisms such as sponges (which have no nervous system) and cnidarians (which have a diffuse nervous system consisting of a nerve net), all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body plan (that is, left and right sides that are approximate mirror images of each other). All bilaterians are thought to have descended from a common ancestor that appeared late in the Cryogenian period, 700–650 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body. At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates. The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, such as vertebrates, it is a large and very complex organ. Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain".
There are a few types of existing bilaterians that lack a recognizable brain, including echinoderms and tunicates. It has not been definitively established whether the existence of these brainless species indicates that the earliest bilaterians lacked a brain, or whether their ancestors evolved in a way that led to the disappearance of a previously existing brain structure.
Invertebrates
This category includes tardigrades, arthropods, molluscs, and numerous types of worms. The diversity of invertebrate body plans is matched by an equal diversity in brain structures. | Brain | Wikipedia | 402 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Two groups of invertebrates have notably complex brains: arthropods (insects, crustaceans, arachnids, and others), and cephalopods (octopuses, squids, and similar molluscs). The brains of arthropods and cephalopods arise from twin parallel nerve cords that extend through the body of the animal. Arthropods have a central brain, the supraesophageal ganglion, with three divisions and large optical lobes behind each eye for visual processing. Cephalopods such as the octopus and squid have the largest brains of any invertebrates. | Brain | Wikipedia | 127 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
There are several invertebrate species whose brains have been studied intensively because they have properties that make them convenient for experimental work:
Fruit flies (Drosophila), because of the large array of techniques available for studying their genetics, have been a natural subject for studying the role of genes in brain development. In spite of the large evolutionary distance between insects and mammals, many aspects of Drosophila neurogenetics have been shown to be relevant to humans. The first biological clock genes, for example, were identified by examining Drosophila mutants that showed disrupted daily activity cycles. A search in the genomes of vertebrates revealed a set of analogous genes, which were found to play similar roles in the mouse biological clock—and therefore almost certainly in the human biological clock as well. Studies done on Drosophila, also show that most neuropil regions of the brain are continuously reorganized throughout life in response to specific living conditions.
The nematode worm Caenorhabditis elegans, like Drosophila, has been studied largely because of its importance in genetics. In the early 1970s, Sydney Brenner chose it as a model organism for studying the way that genes control development. One of the advantages of working with this worm is that the body plan is very stereotyped: the nervous system of the hermaphrodite contains exactly 302 neurons, always in the same places, making identical synaptic connections in every worm. Brenner's team sliced worms into thousands of ultrathin sections and photographed each one under an electron microscope, then visually matched fibers from section to section, to map out every neuron and synapse in the entire body. The complete neuronal wiring diagram of C.elegans – its connectome was achieved. Nothing approaching this level of detail is available for any other organism, and the information gained has enabled a multitude of studies that would otherwise have not been possible.
The sea slug Aplysia californica was chosen by Nobel Prize-winning neurophysiologist Eric Kandel as a model for studying the cellular basis of learning and memory, because of the simplicity and accessibility of its nervous system, and it has been examined in hundreds of experiments.
Vertebrates | Brain | Wikipedia | 459 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The first vertebrates appeared over 500 million years ago (Mya) during the Cambrian period, and may have resembled the modern jawless fish (hagfish and lamprey) in form. Jawed vertebrates appeared by 445 Mya, tetrapods by 350 Mya, amniotes by 310 Mya and mammaliaforms by 200 Mya (approximately). Each vertebrate clade has an equally long evolutionary history, but the brains of modern fish, amphibians, reptiles, birds and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical structures, but many are rudimentary in the hagfish, whereas in mammals the foremost part (forebrain, especially the telencephalon) is greatly developed and expanded.
Brains are most commonly compared in terms of their mass. The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. As a rule of thumb, brain size increases with body size, but not in a simple linear proportion. In general, smaller animals tend to have proportionally larger brains, measured as a fraction of body size. For mammals, the relationship between brain volume and body mass essentially follows a power law with an exponent of about 0.75. This formula describes the central tendency, but every family of mammals departs from it to some degree, in a way that reflects in part the complexity of their behavior. For example, primates have brains 5 to 10 times larger than the formula predicts. Predators, who have to implement various hunting strategies against the ever changing anti-predator adaptations, tend to have larger brains relative to body size than their prey. | Brain | Wikipedia | 355 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three vesicular swellings at the front end of the neural tube; these swellings eventually become the forebrain (prosencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon), respectively. At the earliest stages of brain development, the three areas are roughly equal in size. In many aquatic/semiaquatic vertebrates such as fish and amphibians, the three parts remain similar in size in adults, but in terrestrial tetrapods such as mammals, the forebrain becomes much larger than the other parts, the hindbrain develops a bulky dorsal extension known as the cerebellum, and the midbrain becomes very small as a result.
The brains of vertebrates are made of very soft tissue. Living brain tissue is pinkish on the outside and mostly white on the inside, with subtle variations in color. Vertebrate brains are surrounded by a system of connective tissue membranes called meninges, which separate the skull from the brain. Cerebral arteries pierce the outer two layers of the meninges, the dura and arachnoid mater, into the subarachnoid space and perfuse the brain parenchyma via arterioles perforating into the innermost layer of the meninges, the pia mater. The endothelial cells in the cerebral blood vessel walls are joined tightly to one another, forming the blood–brain barrier, which blocks the passage of many toxins and pathogens (though at the same time blocking antibodies and some drugs, thereby presenting special challenges in treatment of diseases of the brain). As a result of the osmotic restriction by the blood-brain barrier, the metabolites within the brain are cleared mostly by bulk flow of the cerebrospinal fluid within the glymphatic system instead of via venules like other parts of the body. | Brain | Wikipedia | 429 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Neuroanatomists usually divide the vertebrate brain into six main subregions: the telencephalon (the cerebral hemispheres), diencephalon (thalamus and hypothalamus), mesencephalon (midbrain), cerebellum, pons and medulla oblongata, with the midbrain, pons and medulla often collectively called the brainstem. Each of these areas has a complex internal structure. Some parts, such as the cerebral cortex and the cerebellar cortex, are folded into convoluted gyri and sulci in order to maximize surface area within the available intracranial space. Other parts, such as the thalamus and hypothalamus, consist of many small clusters of nuclei known as "ganglia". Thousands of distinguishable areas can be identified within the vertebrate brain based on fine distinctions of neural structure, chemistry, and connectivity.
Although the same basic components are present in all vertebrate brains, some branches of vertebrate evolution have led to substantial distortions of brain geometry, especially in the forebrain area. The brain of a shark shows the basic components in a straightforward way, but in teleost fishes (the great majority of existing fish species), the forebrain has become "everted", like a sock turned inside out. In birds, there are also major changes in forebrain structure. These distortions can make it difficult to match brain components from one species with those of another species.
Here is a list of some of the most important vertebrate brain components, along with a brief description of their functions as currently understood: | Brain | Wikipedia | 349 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The medulla, along with the spinal cord, contains many small nuclei involved in a wide variety of sensory and involuntary motor functions such as vomiting, heart rate and digestive processes.
The pons lies in the brainstem directly above the medulla. Among other things, it contains nuclei that control often voluntary but simple acts such as sleep, respiration, swallowing, bladder function, equilibrium, eye movement, facial expressions, and posture.
The hypothalamus is a small region at the base of the forebrain, whose complexity and importance belies its size. It is composed of numerous small nuclei, each with distinct connections and neurochemistry. The hypothalamus is engaged in additional involuntary or partially voluntary acts such as sleep and wake cycles, eating and drinking, and the release of some hormones.
The thalamus is a collection of nuclei with diverse functions: some are involved in relaying information to and from the cerebral hemispheres, while others are involved in motivation. The subthalamic area (zona incerta) seems to contain action-generating systems for several types of "consummatory" behaviors such as eating, drinking, defecation, and copulation.
The cerebellum modulates the outputs of other brain systems, whether motor-related or thought related, to make them certain and precise. Removal of the cerebellum does not prevent an animal from doing anything in particular, but it makes actions hesitant and clumsy. This precision is not built-in but learned by trial and error. The muscle coordination learned while riding a bicycle is an example of a type of neural plasticity that may take place largely within the cerebellum. 10% of the brain's total volume consists of the cerebellum and 50% of all neurons are held within its structure.
The optic tectum allows actions to be directed toward points in space, most commonly in response to visual input. In mammals, it is usually referred to as the superior colliculus, and its best-studied function is to direct eye movements. It also directs reaching movements and other object-directed actions. It receives strong visual inputs, but also inputs from other senses that are useful in directing actions, such as auditory input in owls and input from the thermosensitive pit organs in snakes. In some primitive fishes, such as lampreys, this region is the largest part of the brain. The superior colliculus is part of the midbrain. | Brain | Wikipedia | 507 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The pallium is a layer of grey matter that lies on the surface of the forebrain and is the most complex and most recent evolutionary development of the brain as an organ. In reptiles and mammals, it is called the cerebral cortex. Multiple functions involve the pallium, including smell and spatial memory. In mammals, where it becomes so large as to dominate the brain, it takes over functions from many other brain areas. In many mammals, the cerebral cortex consists of folded bulges called gyri that create deep furrows or fissures called sulci. The folds increase the surface area of the cortex and therefore increase the amount of gray matter and the amount of information that can be stored and processed.
The hippocampus, strictly speaking, is found only in mammals. However, the area it derives from, the medial pallium, has counterparts in all vertebrates. There is evidence that this part of the brain is involved in complex events such as spatial memory and navigation in fishes, birds, reptiles, and mammals.
The basal ganglia are a group of interconnected structures in the forebrain. The primary function of the basal ganglia appears to be action selection: they send inhibitory signals to all parts of the brain that can generate motor behaviors, and in the right circumstances can release the inhibition, so that the action-generating systems are able to execute their actions. Reward and punishment exert their most important neural effects by altering connections within the basal ganglia.
The olfactory bulb is a special structure that processes olfactory sensory signals and sends its output to the olfactory part of the pallium. It is a major brain component in many vertebrates, but is greatly reduced in humans and other primates (whose senses are dominated by information acquired by sight rather than smell). | Brain | Wikipedia | 366 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Reptiles
Modern reptiles and mammals diverged from a common ancestor around 320 million years ago. The number of extant reptiles far exceeds the number of mammalian species, with 11,733 recognized species of reptiles compared to 5,884 extant mammals. Along with the species diversity, reptiles have diverged in terms of external morphology, from limbless to tetrapod gliders to armored chelonians, reflecting adaptive radiation to a diverse array of environments.
Morphological differences are reflected in the nervous system phenotype, such as: absence of lateral motor column neurons in snakes, which innervate limb muscles controlling limb movements; absence of motor neurons that innervate trunk muscles in tortoises; presence of innervation from the trigeminal nerve to pit organs responsible to infrared detection in snakes. Variation in size, weight, and shape of the brain can be found within reptiles. For instance, crocodilians have the largest brain volume to body weight proportion, followed by turtles, lizards, and snakes. Reptiles vary in the investment in different brain sections. Crocodilians have the largest telencephalon, while snakes have the smallest. Turtles have the largest diencephalon per body weight whereas crocodilians have the smallest. On the other hand, lizards have the largest mesencephalon.
Yet their brains share several characteristics revealed by recent anatomical, molecular, and ontogenetic studies. Vertebrates share the highest levels of similarities during embryological development, controlled by conserved transcription factors and signaling centers, including gene expression, morphological and cell type differentiation. In fact, high levels of transcriptional factors can be found in all areas of the brain in reptiles and mammals, with shared neuronal clusters enlightening brain evolution. Conserved transcription factors elucidate that evolution acted in different areas of the brain by either retaining similar morphology and function, or diversifying it. | Brain | Wikipedia | 382 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Anatomically, the reptilian brain has less subdivisions than the mammalian brain, however it has numerous conserved aspects including the organization of the spinal cord and cranial nerve, as well as elaborated brain pattern of organization. Elaborated brains are characterized by migrated neuronal cell bodies away from the periventricular matrix, region of neuronal development, forming organized nuclear groups. Aside from reptiles and mammals, other vertebrates with elaborated brains include hagfish, galeomorph sharks, skates, rays, teleosts, and birds. Overall elaborated brains are subdivided in forebrain, midbrain, and hindbrain.
The hindbrain coordinates and integrates sensory and motor inputs and outputs responsible for, but not limited to, walking, swimming, or flying. It contains input and output axons interconnecting the spinal cord, midbrain and forebrain transmitting information from the external and internal environments. The midbrain links sensory, motor, and integrative components received from the hindbrain, connecting it to the forebrain. The tectum, which includes the optic tectum and torus semicircularis, receives auditory, visual, and somatosensory inputs, forming integrated maps of the sensory and visual space around the animal. The tegmentum receives incoming sensory information and forwards motor responses to and from the forebrain. The isthmus connects the hindbrain with midbrain. The forebrain region is particularly well developed, is further divided into diencephalon and telencephalon. Diencephalon is related to regulation of eye and body movement in response to visual stimuli, sensory information, circadian rhythms, olfactory input, and autonomic nervous system.Telencephalon is related to control of movements, neurotransmitters and neuromodulators responsible for integrating inputs and transmitting outputs are present, sensory systems, and cognitive functions.
Birds
Mammals
The most obvious difference between the brains of mammals and other vertebrates is their size. On average, a mammal has a brain roughly twice as large as that of a bird of the same body size, and ten times as large as that of a reptile of the same body size. | Brain | Wikipedia | 462 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain, which is greatly enlarged and also altered in structure. The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the cerebrum is lined with a comparatively simple three-layered structure called the pallium. In mammals, the pallium evolves into a complex six-layered structure called neocortex or isocortex. Several areas at the edge of the neocortex, including the hippocampus and amygdala, are also much more extensively developed in mammals than in other vertebrates.
The elaboration of the cerebral cortex carries with it changes to other brain areas. The superior colliculus, which plays a major role in visual control of behavior in most vertebrates, shrinks to a small size in mammals, and many of its functions are taken over by visual areas of the cerebral cortex. The cerebellum of mammals contains a large portion (the neocerebellum) dedicated to supporting the cerebral cortex, which has no counterpart in other vertebrates.
In placentals, there is a wide nerve tract connecting the cerebral hemispheres called the corpus callosum.
Primates
The brains of humans and other primates contain the same structures as the brains of other mammals, but are generally larger in proportion to body size. The encephalization quotient (EQ) is used to compare brain sizes across species. It takes into account the nonlinearity of the brain-to-body relationship. Humans have an average EQ in the 7-to-8 range, while most other primates have an EQ in the 2-to-3 range. Dolphins have values higher than those of primates other than humans, but nearly all other mammals have EQ values that are substantially lower. | Brain | Wikipedia | 421 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Most of the enlargement of the primate brain comes from a massive expansion of the cerebral cortex, especially the prefrontal cortex and the parts of the cortex involved in vision. The visual processing network of primates includes at least 30 distinguishable brain areas, with a complex web of interconnections. It has been estimated that visual processing areas occupy more than half of the total surface of the primate neocortex. The prefrontal cortex carries out functions that include planning, working memory, motivation, attention, and executive control. It takes up a much larger proportion of the brain for primates than for other species, and an especially large fraction of the human brain.
Development
The brain develops in an intricately orchestrated sequence of stages. It changes in shape from a simple swelling at the front of the nerve cord in the earliest embryonic stages, to a complex array of areas and connections. Neurons are created in special zones that contain stem cells, and then migrate through the tissue to reach their ultimate locations. Once neurons have positioned themselves, their axons sprout and navigate through the brain, branching and extending as they go, until the tips reach their targets and form synaptic connections. In a number of parts of the nervous system, neurons and synapses are produced in excessive numbers during the early stages, and then the unneeded ones are pruned away. | Brain | Wikipedia | 280 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
For vertebrates, the early stages of neural development are similar across all species. As the embryo transforms from a round blob of cells into a wormlike structure, a narrow strip of ectoderm running along the midline of the back is induced to become the neural plate, the precursor of the nervous system. The neural plate folds inward to form the neural groove, and then the lips that line the groove merge to enclose the neural tube, a hollow cord of cells with a fluid-filled ventricle at the center. At the front end, the ventricles and cord swell to form three vesicles that are the precursors of the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). At the next stage, the forebrain splits into two vesicles called the telencephalon (which will contain the cerebral cortex, basal ganglia, and related structures) and the diencephalon (which will contain the thalamus and hypothalamus). At about the same time, the hindbrain splits into the metencephalon (which will contain the cerebellum and pons) and the myelencephalon (which will contain the medulla oblongata). Each of these areas contains proliferative zones where neurons and glial cells are generated; the resulting cells then migrate, sometimes for long distances, to their final positions.
Once a neuron is in place, it extends dendrites and an axon into the area around it. Axons, because they commonly extend a great distance from the cell body and need to reach specific targets, grow in a particularly complex way. The tip of a growing axon consists of a blob of protoplasm called a growth cone, studded with chemical receptors. These receptors sense the local environment, causing the growth cone to be attracted or repelled by various cellular elements, and thus to be pulled in a particular direction at each point along its path. The result of this pathfinding process is that the growth cone navigates through the brain until it reaches its destination area, where other chemical cues cause it to begin generating synapses. Considering the entire brain, thousands of genes create products that influence axonal pathfinding. | Brain | Wikipedia | 487 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The synaptic network that finally emerges is only partly determined by genes, though. In many parts of the brain, axons initially "overgrow", and then are "pruned" by mechanisms that depend on neural activity. In the projection from the eye to the midbrain, for example, the structure in the adult contains a very precise mapping, connecting each point on the surface of the retina to a corresponding point in a midbrain layer. In the first stages of development, each axon from the retina is guided to the right general vicinity in the midbrain by chemical cues, but then branches very profusely and makes initial contact with a wide swath of midbrain neurons. The retina, before birth, contains special mechanisms that cause it to generate waves of activity that originate spontaneously at a random point and then propagate slowly across the retinal layer. These waves are useful because they cause neighboring neurons to be active at the same time; that is, they produce a neural activity pattern that contains information about the spatial arrangement of the neurons. This information is exploited in the midbrain by a mechanism that causes synapses to weaken, and eventually vanish, if activity in an axon is not followed by activity of the target cell. The result of this sophisticated process is a gradual tuning and tightening of the map, leaving it finally in its precise adult form.
Similar things happen in other brain areas: an initial synaptic matrix is generated as a result of genetically determined chemical guidance, but then gradually refined by activity-dependent mechanisms, partly driven by internal dynamics, partly by external sensory inputs. In some cases, as with the retina-midbrain system, activity patterns depend on mechanisms that operate only in the developing brain, and apparently exist solely to guide development. | Brain | Wikipedia | 371 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
In humans and many other mammals, new neurons are created mainly before birth, and the infant brain contains substantially more neurons than the adult brain. There are, however, a few areas where new neurons continue to be generated throughout life. The two areas for which adult neurogenesis is well established are the olfactory bulb, which is involved in the sense of smell, and the dentate gyrus of the hippocampus, where there is evidence that the new neurons play a role in storing newly acquired memories. With these exceptions, however, the set of neurons that is present in early childhood is the set that is present for life. Glial cells are different: as with most types of cells in the body, they are generated throughout the lifespan.
There has long been debate about whether the qualities of mind, personality, and intelligence can be attributed to heredity or to upbringing. Although many details remain to be settled, neuroscience shows that both factors are important. Genes determine both the general form of the brain and how it reacts to experience, but experience is required to refine the matrix of synaptic connections, resulting in greatly increased complexity. The presence or absence of experience is critical at key periods of development. Additionally, the quantity and quality of experience are important. For example, animals raised in enriched environments demonstrate thick cerebral cortices, indicating a high density of synaptic connections, compared to animals with restricted levels of stimulation.
Physiology
The functions of the brain depend on the ability of neurons to transmit electrochemical signals to other cells, and their ability to respond appropriately to electrochemical signals received from other cells. The electrical properties of neurons are controlled by a wide variety of biochemical and metabolic processes, most notably the interactions between neurotransmitters and receptors that take place at synapses. | Brain | Wikipedia | 366 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Neurotransmitters and receptors
Neurotransmitters are chemicals that are released at synapses when the local membrane is depolarised and Ca2+ enters into the cell, typically when an action potential arrives at the synapse – neurotransmitters attach themselves to receptor molecules on the membrane of the synapse's target cell (or cells), and thereby alter the electrical or chemical properties of the receptor molecules. With few exceptions, each neuron in the brain releases the same chemical neurotransmitter, or combination of neurotransmitters, at all the synaptic connections it makes with other neurons; this rule is known as Dale's principle. Thus, a neuron can be characterized by the neurotransmitters that it releases. The great majority of psychoactive drugs exert their effects by altering specific neurotransmitter systems. This applies to drugs such as cannabinoids, nicotine, heroin, cocaine, alcohol, fluoxetine, chlorpromazine, and many others.
The two neurotransmitters that are most widely found in the vertebrate brain are glutamate, which almost always exerts excitatory effects on target neurons, and gamma-aminobutyric acid (GABA), which is almost always inhibitory. Neurons using these transmitters can be found in nearly every part of the brain. Because of their ubiquity, drugs that act on glutamate or GABA tend to have broad and powerful effects. Some general anesthetics act by reducing the effects of glutamate; most tranquilizers exert their sedative effects by enhancing the effects of GABA.
There are dozens of other chemical neurotransmitters that are used in more limited areas of the brain, often areas dedicated to a particular function. Serotonin, for example—the primary target of many antidepressant drugs and many dietary aids—comes exclusively from a small brainstem area called the raphe nuclei. Norepinephrine, which is involved in arousal, comes exclusively from a nearby small area called the locus coeruleus. Other neurotransmitters such as acetylcholine and dopamine have multiple sources in the brain but are not as ubiquitously distributed as glutamate and GABA.
Electrical activity | Brain | Wikipedia | 499 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
As a side effect of the electrochemical processes used by neurons for signaling, brain tissue generates electric fields when it is active. When large numbers of neurons show synchronized activity, the electric fields that they generate can be large enough to detect outside the skull, using electroencephalography (EEG) or magnetoencephalography (MEG). EEG recordings, along with recordings made from electrodes implanted inside the brains of animals such as rats, show that the brain of a living animal is constantly active, even during sleep. Each part of the brain shows a mixture of rhythmic and nonrhythmic activity, which may vary according to behavioral state. In mammals, the cerebral cortex tends to show large slow delta waves during sleep, faster alpha waves when the animal is awake but inattentive, and chaotic-looking irregular activity when the animal is actively engaged in a task, called beta and gamma waves. During an epileptic seizure, the brain's inhibitory control mechanisms fail to function and electrical activity rises to pathological levels, producing EEG traces that show large wave and spike patterns not seen in a healthy brain. Relating these population-level patterns to the computational functions of individual neurons is a major focus of current research in neurophysiology.
Metabolism
All vertebrates have a blood–brain barrier that allows metabolism inside the brain to operate differently from metabolism in other parts of the body. The neurovascular unit regulates cerebral blood flow so that activated neurons can be supplied with energy. Glial cells play a major role in brain metabolism by controlling the chemical composition of the fluid that surrounds neurons, including levels of ions and nutrients. | Brain | Wikipedia | 337 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Brain tissue consumes a large amount of energy in proportion to its volume, so large brains place severe metabolic demands on animals. The need to limit body weight in order, for example, to fly, has apparently led to selection for a reduction of brain size in some species, such as bats. Most of the brain's energy consumption goes into sustaining the electric charge (membrane potential) of neurons. Most vertebrate species devote between 2% and 8% of basal metabolism to the brain. In primates, however, the percentage is much higher—in humans it rises to 20–25%. The energy consumption of the brain does not vary greatly over time, but active regions of the cerebral cortex consume somewhat more energy than inactive regions; this forms the basis for the functional brain imaging methods of PET, fMRI, and NIRS. The brain typically gets most of its energy from oxygen-dependent metabolism of glucose (i.e., blood sugar), but ketones provide a major alternative source, together with contributions from medium chain fatty acids (caprylic and heptanoic acids), lactate, acetate, and possibly amino acids.
Function
Information from the sense organs is collected in the brain. There it is used to determine what actions the organism is to take. The brain processes the raw data to extract information about the structure of the environment. Next it combines the processed information with information about the current needs of the animal and with memory of past circumstances. Finally, on the basis of the results, it generates motor response patterns. These signal-processing tasks require intricate interplay between a variety of functional subsystems.
The function of the brain is to provide coherent control over the actions of an animal. A centralized brain allows groups of muscles to be co-activated in complex patterns; it also allows stimuli impinging on one part of the body to evoke responses in other parts, and it can prevent different parts of the body from acting at cross-purposes to each other.
Perception
The human brain is provided with information about light, sound, the chemical composition of the atmosphere, temperature, the position of the body in space (proprioception), the chemical composition of the bloodstream, and more. In other animals additional senses are present, such as the infrared heat-sense of snakes, the magnetic field sense of some birds, or the electric field sense mainly seen in aquatic animals. | Brain | Wikipedia | 485 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Each sensory system begins with specialized receptor cells, such as photoreceptor cells in the retina of the eye, or vibration-sensitive hair cells in the cochlea of the ear. The axons of sensory receptor cells travel into the spinal cord or brain, where they transmit their signals to a first-order sensory nucleus dedicated to one specific sensory modality. This primary sensory nucleus sends information to higher-order sensory areas that are dedicated to the same modality. Eventually, via a way-station in the thalamus, the signals are sent to the cerebral cortex, where they are processed to extract the relevant features, and integrated with signals coming from other sensory systems.
Motor control
Motor systems are areas of the brain that are involved in initiating body movements, that is, in activating muscles. Except for the muscles that control the eye, which are driven by nuclei in the midbrain, all the voluntary muscles in the body are directly innervated by motor neurons in the spinal cord and hindbrain. Spinal motor neurons are controlled both by neural circuits intrinsic to the spinal cord, and by inputs that descend from the brain. The intrinsic spinal circuits implement many reflex responses, and contain pattern generators for rhythmic movements such as walking or swimming. The descending connections from the brain allow for more sophisticated control.
The brain contains several motor areas that project directly to the spinal cord. At the lowest level are motor areas in the medulla and pons, which control stereotyped movements such as walking, breathing, or swallowing. At a higher level are areas in the midbrain, such as the red nucleus, which is responsible for coordinating movements of the arms and legs. At a higher level yet is the primary motor cortex, a strip of tissue located at the posterior edge of the frontal lobe. The primary motor cortex sends projections to the subcortical motor areas, but also sends a massive projection directly to the spinal cord, through the pyramidal tract. This direct corticospinal projection allows for precise voluntary control of the fine details of movements. Other motor-related brain areas exert secondary effects by projecting to the primary motor areas. Among the most important secondary areas are the premotor cortex, supplementary motor area, basal ganglia, and cerebellum. In addition to all of the above, the brain and spinal cord contain extensive circuitry to control the autonomic nervous system which controls the movement of the smooth muscle of the body.
Sleep | Brain | Wikipedia | 499 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Many animals alternate between sleeping and waking in a daily cycle. Arousal and alertness are also modulated on a finer time scale by a network of brain areas. A key component of the sleep system is the suprachiasmatic nucleus (SCN), a tiny part of the hypothalamus located directly above the point at which the optic nerves from the two eyes cross. The SCN contains the body's central biological clock. Neurons there show activity levels that rise and fall with a period of about 24 hours, circadian rhythms: these activity fluctuations are driven by rhythmic changes in expression of a set of "clock genes". The SCN continues to keep time even if it is excised from the brain and placed in a dish of warm nutrient solution, but it ordinarily receives input from the optic nerves, through the retinohypothalamic tract (RHT), that allows daily light-dark cycles to calibrate the clock.
The SCN projects to a set of areas in the hypothalamus, brainstem, and midbrain that are involved in implementing sleep-wake cycles. An important component of the system is the reticular formation, a group of neuron-clusters scattered diffusely through the core of the lower brain. Reticular neurons send signals to the thalamus, which in turn sends activity-level-controlling signals to every part of the cortex. Damage to the reticular formation can produce a permanent state of coma.
Sleep involves great changes in brain activity. Until the 1950s it was generally believed that the brain essentially shuts off during sleep, but this is now known to be far from true; activity continues, but patterns become very different. There are two types of sleep: REM sleep (with dreaming) and NREM (non-REM, usually without dreaming) sleep, which repeat in slightly varying patterns throughout a sleep episode. Three broad types of distinct brain activity patterns can be measured: REM, light NREM and deep NREM. During deep NREM sleep, also called slow wave sleep, activity in the cortex takes the form of large synchronized waves, whereas in the waking state it is noisy and desynchronized. Levels of the neurotransmitters norepinephrine and serotonin drop during slow wave sleep, and fall almost to zero during REM sleep; levels of acetylcholine show the reverse pattern.
Homeostasis | Brain | Wikipedia | 502 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
For any animal, survival requires maintaining a variety of parameters of bodily state within a limited range of variation: these include temperature, water content, salt concentration in the bloodstream, blood glucose levels, blood oxygen level, and others. The ability of an animal to regulate the internal environment of its body—the milieu intérieur, as the pioneering physiologist Claude Bernard called it—is known as homeostasis (Greek for "standing still"). Maintaining homeostasis is a crucial function of the brain. The basic principle that underlies homeostasis is negative feedback: any time a parameter diverges from its set-point, sensors generate an error signal that evokes a response that causes the parameter to shift back toward its optimum value. (This principle is widely used in engineering, for example in the control of temperature using a thermostat.)
In vertebrates, the part of the brain that plays the greatest role is the hypothalamus, a small region at the base of the forebrain whose size does not reflect its complexity or the importance of its function. The hypothalamus is a collection of small nuclei, most of which are involved in basic biological functions. Some of these functions relate to arousal or to social interactions such as sexuality, aggression, or maternal behaviors; but many of them relate to homeostasis. Several hypothalamic nuclei receive input from sensors located in the lining of blood vessels, conveying information about temperature, sodium level, glucose level, blood oxygen level, and other parameters. These hypothalamic nuclei send output signals to motor areas that can generate actions to rectify deficiencies. Some of the outputs also go to the pituitary gland, a tiny gland attached to the brain directly underneath the hypothalamus. The pituitary gland secretes hormones into the bloodstream, where they circulate throughout the body and induce changes in cellular activity.
Motivation | Brain | Wikipedia | 401 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The individual animals need to express survival-promoting behaviors, such as seeking food, water, shelter, and a mate. The motivational system in the brain monitors the current state of satisfaction of these goals, and activates behaviors to meet any needs that arise. The motivational system works largely by a reward–punishment mechanism. When a particular behavior is followed by favorable consequences, the reward mechanism in the brain is activated, which induces structural changes inside the brain that cause the same behavior to be repeated later, whenever a similar situation arises. Conversely, when a behavior is followed by unfavorable consequences, the brain's punishment mechanism is activated, inducing structural changes that cause the behavior to be suppressed when similar situations arise in the future.
Most organisms studied to date use a reward–punishment mechanism: for instance, worms and insects can alter their behavior to seek food sources or to avoid dangers. In vertebrates, the reward-punishment system is implemented by a specific set of brain structures, at the heart of which lie the basal ganglia, a set of interconnected areas at the base of the forebrain. The basal ganglia are the central site at which decisions are made: the basal ganglia exert a sustained inhibitory control over most of the motor systems in the brain; when this inhibition is released, a motor system is permitted to execute the action it is programmed to carry out. Rewards and punishments function by altering the relationship between the inputs that the basal ganglia receive and the decision-signals that are emitted. The reward mechanism is better understood than the punishment mechanism, because its role in drug abuse has caused it to be studied very intensively. Research has shown that the neurotransmitter dopamine plays a central role: addictive drugs such as cocaine, amphetamine, and nicotine either cause dopamine levels to rise or cause the effects of dopamine inside the brain to be enhanced. | Brain | Wikipedia | 392 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Learning and memory
Almost all animals are capable of modifying their behavior as a result of experience—even the most primitive types of worms. Because behavior is driven by brain activity, changes in behavior must somehow correspond to changes inside the brain. Already in the late 19th century theorists like Santiago Ramón y Cajal argued that the most plausible explanation is that learning and memory are expressed as changes in the synaptic connections between neurons. Until 1970, however, experimental evidence to support the synaptic plasticity hypothesis was lacking. In 1971 Tim Bliss and Terje Lømo published a paper on a phenomenon now called long-term potentiation: the paper showed clear evidence of activity-induced synaptic changes that lasted for at least several days. Since then technical advances have made these sorts of experiments much easier to carry out, and thousands of studies have been made that have clarified the mechanism of synaptic change, and uncovered other types of activity-driven synaptic change in a variety of brain areas, including the cerebral cortex, hippocampus, basal ganglia, and cerebellum. Brain-derived neurotrophic factor (BDNF) and physical activity appear to play a beneficial role in the process.
Neuroscientists currently distinguish several types of learning and memory that are implemented by the brain in distinct ways: | Brain | Wikipedia | 270 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Working memory is the ability of the brain to maintain a temporary representation of information about the task that an animal is currently engaged in. This sort of dynamic memory is thought to be mediated by the formation of cell assemblies—groups of activated neurons that maintain their activity by constantly stimulating one another.
Episodic memory is the ability to remember the details of specific events. This sort of memory can last for a lifetime. Much evidence implicates the hippocampus in playing a crucial role: people with severe damage to the hippocampus sometimes show amnesia, that is, inability to form new long-lasting episodic memories.
Semantic memory is the ability to learn facts and relationships. This sort of memory is probably stored largely in the cerebral cortex, mediated by changes in connections between cells that represent specific types of information.
Instrumental learning is the ability for rewards and punishments to modify behavior. It is implemented by a network of brain areas centered on the basal ganglia.
Motor learning is the ability to refine patterns of body movement by practicing, or more generally by repetition. A number of brain areas are involved, including the premotor cortex, basal ganglia, and especially the cerebellum, which functions as a large memory bank for microadjustments of the parameters of movement.
Research
The field of neuroscience encompasses all approaches that seek to understand the brain and the rest of the nervous system. Psychology seeks to understand mind and behavior, and neurology is the medical discipline that diagnoses and treats diseases of the nervous system. The brain is also the most important organ studied in psychiatry, the branch of medicine that works to study, prevent, and treat mental disorders. Cognitive science seeks to unify neuroscience and psychology with other fields that concern themselves with the brain, such as computer science (artificial intelligence and similar fields) and philosophy. | Brain | Wikipedia | 371 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The oldest method of studying the brain is anatomical, and until the middle of the 20th century, much of the progress in neuroscience came from the development of better cell stains and better microscopes. Neuroanatomists study the large-scale structure of the brain as well as the microscopic structure of neurons and their components, especially synapses. Among other tools, they employ a plethora of stains that reveal neural structure, chemistry, and connectivity. In recent years, the development of immunostaining techniques has allowed investigation of neurons that express specific sets of genes. Also, functional neuroanatomy uses medical imaging techniques to correlate variations in human brain structure with differences in cognition or behavior.
Neurophysiologists study the chemical, pharmacological, and electrical properties of the brain: their primary tools are drugs and recording devices. Thousands of experimentally developed drugs affect the nervous system, some in highly specific ways. Recordings of brain activity can be made using electrodes, either glued to the scalp as in EEG studies, or implanted inside the brains of animals for extracellular recordings, which can detect action potentials generated by individual neurons. Because the brain does not contain pain receptors, it is possible using these techniques to record brain activity from animals that are awake and behaving without causing distress. The same techniques have occasionally been used to study brain activity in human patients with intractable epilepsy, in cases where there was a medical necessity to implant electrodes to localize the brain area responsible for epileptic seizures. Functional imaging techniques such as fMRI are also used to study brain activity; these techniques have mainly been used with human subjects, because they require a conscious subject to remain motionless for long periods of time, but they have the great advantage of being noninvasive. | Brain | Wikipedia | 367 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Another approach to brain function is to examine the consequences of damage to specific brain areas. Even though it is protected by the skull and meninges, surrounded by cerebrospinal fluid, and isolated from the bloodstream by the blood–brain barrier, the delicate nature of the brain makes it vulnerable to numerous diseases and several types of damage. In humans, the effects of strokes and other types of brain damage have been a key source of information about brain function. Because there is no ability to experimentally control the nature of the damage, however, this information is often difficult to interpret. In animal studies, most commonly involving rats, it is possible to use electrodes or locally injected chemicals to produce precise patterns of damage and then examine the consequences for behavior.
Computational neuroscience encompasses two approaches: first, the use of computers to study the brain; second, the study of how brains perform computation. On one hand, it is possible to write a computer program to simulate the operation of a group of neurons by making use of systems of equations that describe their electrochemical activity; such simulations are known as biologically realistic neural networks. On the other hand, it is possible to study algorithms for neural computation by simulating, or mathematically analyzing, the operations of simplified "units" that have some of the properties of neurons but abstract out much of their biological complexity. The computational functions of the brain are studied both by computer scientists and neuroscientists.
Computational neurogenetic modeling is concerned with the study and development of dynamic neuronal models for modeling brain functions with respect to genes and dynamic interactions between genes.
Recent years have seen increasing applications of genetic and genomic techniques to the study of the brain and a focus on the roles of neurotrophic factors and physical activity in neuroplasticity. The most common subjects are mice, because of the availability of technical tools. It is now possible with relative ease to "knock out" or mutate a wide variety of genes, and then examine the effects on brain function. More sophisticated approaches are also being used: for example, using Cre-Lox recombination it is possible to activate or deactivate genes in specific parts of the brain, at specific times. | Brain | Wikipedia | 452 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Recent years have also seen rapid advances in single-cell sequencing technologies, and these have been used to leverage the cellular heterogeneity of the brain as a means of better understanding the roles of distinct cell types in disease and biology (as well as how genomic variants influence individual cell types). In 2024, investigators studied a large integrated dataset of almost 3 million nuclei from the human prefrontal cortext from 388 individuals. In doing so, they annotated 28 cell types to evaluate expression and chromatin variation across gene families and drug targets. They identified about half a million cell type–specific regulatory elements and about 1.5 million single-cell expression quantitative trait loci (i.e., genomic variants with strong statistical associations with changes in gene expression within specific cell types), which were then used to build cell-type regulatory networks (the study also describes cell-to-cell communication networks). These networks were found to manifest cellular changes in aging and neuropsychiatric disorders. As part of the same investigation, a machine learning model was designed to accurately impute single-cell expression (this model prioritized ~250 disease-risk genes and drug targets with associated cell types).
History
The oldest brain to have been discovered was in Armenia in the Areni-1 cave complex. The brain, estimated to be over 5,000 years old, was found in the skull of a 12 to 14-year-old girl. Although the brains were shriveled, they were well preserved due to the climate found inside the cave.
Early philosophers were divided as to whether the seat of the soul lies in the brain or heart. Aristotle favored the heart, and thought that the function of the brain was merely to cool the blood. Democritus, the inventor of the atomic theory of matter, argued for a three-part soul, with intellect in the head, emotion in the heart, and lust near the liver. The unknown author of On the Sacred Disease, a medical treatise in the Hippocratic Corpus, came down unequivocally in favor of the brain, writing: | Brain | Wikipedia | 433 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
The Roman physician Galen also argued for the importance of the brain, and theorized in some depth about how it might work. Galen traced out the anatomical relationships among brain, nerves, and muscles, demonstrating that all muscles in the body are connected to the brain through a branching network of nerves. He postulated that nerves activate muscles mechanically by carrying a mysterious substance he called pneumata psychikon, usually translated as "animal spirits". Galen's ideas were widely known during the Middle Ages, but not much further progress came until the Renaissance, when detailed anatomical study resumed, combined with the theoretical speculations of René Descartes and those who followed him. Descartes, like Galen, thought of the nervous system in hydraulic terms. He believed that the highest cognitive functions are carried out by a non-physical res cogitans, but that the majority of behaviors of humans, and all behaviors of animals, could be explained mechanistically.
The first real progress toward a modern understanding of nervous function, though, came from the investigations of Luigi Galvani (1737–1798), who discovered that a shock of static electricity applied to an exposed nerve of a dead frog could cause its leg to contract. Since that time, each major advance in understanding has followed more or less directly from the development of a new technique of investigation. Until the early years of the 20th century, the most important advances were derived from new methods for staining cells. Particularly critical was the invention of the Golgi stain, which (when correctly used) stains only a small fraction of neurons, but stains them in their entirety, including cell body, dendrites, and axon. Without such a stain, brain tissue under a microscope appears as an impenetrable tangle of protoplasmic fibers, in which it is impossible to determine any structure. In the hands of Camillo Golgi, and especially of the Spanish neuroanatomist Santiago Ramón y Cajal, the new stain revealed hundreds of distinct types of neurons, each with its own unique dendritic structure and pattern of connectivity. | Brain | Wikipedia | 425 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
In the first half of the 20th century, advances in electronics enabled investigation of the electrical properties of nerve cells, culminating in work by Alan Hodgkin, Andrew Huxley, and others on the biophysics of the action potential, and the work of Bernard Katz and others on the electrochemistry of the synapse. These studies complemented the anatomical picture with a conception of the brain as a dynamic entity. Reflecting the new understanding, in 1942 Charles Sherrington visualized the workings of the brain waking from sleep:
The invention of electronic computers in the 1940s, along with the development of mathematical information theory, led to a realization that brains can potentially be understood as information processing systems. This concept formed the basis of the field of cybernetics, and eventually gave rise to the field now known as computational neuroscience. The earliest attempts at cybernetics were somewhat crude in that they treated the brain as essentially a digital computer in disguise, as for example in John von Neumann's 1958 book, The Computer and the Brain. Over the years, though, accumulating information about the electrical responses of brain cells recorded from behaving animals has steadily moved theoretical concepts in the direction of increasing realism.
One of the most influential early contributions was a 1959 paper titled What the frog's eye tells the frog's brain: the paper examined the visual responses of neurons in the retina and optic tectum of frogs, and came to the conclusion that some neurons in the tectum of the frog are wired to combine elementary responses in a way that makes them function as "bug perceivers". A few years later David Hubel and Torsten Wiesel discovered cells in the primary visual cortex of monkeys that become active when sharp edges move across specific points in the field of view—a discovery for which they won a Nobel Prize. Follow-up studies in higher-order visual areas found cells that detect binocular disparity, color, movement, and aspects of shape, with areas located at increasing distances from the primary visual cortex showing increasingly complex responses. Other investigations of brain areas unrelated to vision have revealed cells with a wide variety of response correlates, some related to memory, some to abstract types of cognition such as space. | Brain | Wikipedia | 451 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Theorists have worked to understand these response patterns by constructing mathematical models of neurons and neural networks, which can be simulated using computers. Some useful models are abstract, focusing on the conceptual structure of neural algorithms rather than the details of how they are implemented in the brain; other models attempt to incorporate data about the biophysical properties of real neurons. No model on any level is yet considered to be a fully valid description of brain function, though. The essential difficulty is that sophisticated computation by neural networks requires distributed processing in which hundreds or thousands of neurons work cooperatively—current methods of brain activity recording are only capable of isolating action potentials from a few dozen neurons at a time.
Furthermore, even single neurons appear to be complex and capable of performing computations. So, brain models that do not reflect this are too abstract to be representative of brain operation; models that do try to capture this are very computationally expensive and arguably intractable with present computational resources. However, the Human Brain Project is trying to build a realistic, detailed computational model of the entire human brain. The wisdom of this approach has been publicly contested, with high-profile scientists on both sides of the argument.
In the second half of the 20th century, developments in chemistry, electron microscopy, genetics, computer science, functional brain imaging, and other fields progressively opened new windows into brain structure and function. In the United States, the 1990s were officially designated as the "Decade of the Brain" to commemorate advances made in brain research, and to promote funding for such research.
In the 21st century, these trends have continued, and several new approaches have come into prominence, including multielectrode recording, which allows the activity of many brain cells to be recorded all at the same time; genetic engineering, which allows molecular components of the brain to be altered experimentally; genomics, which allows variations in brain structure to be correlated with variations in DNA properties and neuroimaging.
Society and culture
As food
Animal brains are used as food in numerous cuisines.
In rituals
Some archaeological evidence suggests that the mourning rituals of European Neanderthals also involved the consumption of the brain.
The Fore people of Papua New Guinea are known to eat human brains. In funerary rituals, those close to the dead would eat the brain of the deceased to create a sense of immortality. A prion disease called kuru has been traced to this. | Brain | Wikipedia | 482 | 3717 | https://en.wikipedia.org/wiki/Brain | Biology and health sciences | Biology | null |
Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limited to 2.5 milliwatts, giving it a very short range of up to . It employs UHF radio waves in the ISM bands, from 2.402GHz to 2.48GHz. It is mainly used as an alternative to wired connections to exchange files between nearby portable devices and connect cell phones and music players with wireless headphones, wireless speakers, HIFI systems, car audio and wireless transmission between TVs and soundbars.
Bluetooth is managed by the Bluetooth Special Interest Group (SIG), which has more than 35,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics. The IEEE standardized Bluetooth as IEEE 802.15.1 but no longer maintains the standard. The Bluetooth SIG oversees the development of the specification, manages the qualification program, and protects the trademarks. A manufacturer must meet Bluetooth SIG standards to market it as a Bluetooth device. A network of patents applies to the technology, which is licensed to individual qualifying devices. , 4.7 billion Bluetooth integrated circuit chips are shipped annually. Bluetooth was first demonstrated in space in 2024, an early test envisioned to enhance IoT capabilities.
Etymology
The name "Bluetooth" was proposed in 1997 by Jim Kardach of Intel, one of the founders of the Bluetooth SIG. The name was inspired by a conversation with Sven Mattisson who related Scandinavian history through tales from Frans G. Bengtsson's The Long Ships, a historical novel about Vikings and the 10th-century Danish king Harald Bluetooth. Upon discovering a picture of the runestone of Harald Bluetooth in the book A History of the Vikings by Gwyn Jones, Kardach proposed Bluetooth as the codename for the short-range wireless program which is now called Bluetooth.
According to Bluetooth's official website,
Bluetooth is the Anglicised version of the Scandinavian Blåtand/Blåtann (or in Old Norse blátǫnn). It was the epithet of King Harald Bluetooth, who united the disparate
Danish tribes into a single kingdom; Kardach chose the name to imply that Bluetooth similarly unites communication protocols. | Bluetooth | Wikipedia | 492 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
The Bluetooth logo is a bind rune merging the Younger Futhark runes (ᚼ, Hagall) and (ᛒ, Bjarkan), Harald's initials.
History
The development of the "short-link" radio technology, later named Bluetooth, was initiated in 1989 by Nils Rydbeck, CTO at Ericsson Mobile in Lund, Sweden. The purpose was to develop wireless headsets, according to two inventions by Johan Ullman, and . Nils Rydbeck tasked Tord Wingren with specifying and Dutchman Jaap Haartsen and Sven Mattisson with developing. Both were working for Ericsson in Lund. Principal design and development began in 1994 and by 1997 the team had a workable solution. From 1997 Örjan Johansson became the project leader and propelled the technology and standardization.
In 1997, Adalio Sanchez, then head of IBM ThinkPad product R&D, approached Nils Rydbeck about collaborating on integrating a mobile phone into a ThinkPad notebook. The two assigned engineers from Ericsson and IBM studied the idea. The conclusion was that power consumption on cellphone technology at that time was too high to allow viable integration into a notebook and still achieve adequate battery life. Instead, the two companies agreed to integrate Ericsson's short-link technology on both a ThinkPad notebook and an Ericsson phone to accomplish the goal.
Since neither IBM ThinkPad notebooks nor Ericsson phones were the market share leaders in their respective markets at that time, Adalio Sanchez and Nils Rydbeck agreed to make the short-link technology an open industry standard to permit each player maximum market access. Ericsson contributed the short-link radio technology, and IBM contributed patents around the logical layer. Adalio Sanchez of IBM then recruited Stephen Nachtsheim of Intel to join and then Intel also recruited Toshiba and Nokia. In May 1998, the Bluetooth SIG was launched with IBM and Ericsson as the founding signatories and a total of five members: Ericsson, Intel, Nokia, Toshiba, and IBM. | Bluetooth | Wikipedia | 416 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
The first Bluetooth device was revealed in 1999. It was a hands-free mobile headset that earned the "Best of show Technology Award" at COMDEX. The first Bluetooth mobile phone was the unreleased prototype Ericsson T36, though it was the revised Ericsson model T39 that actually made it to store shelves in June 2001. However Ericsson released the R520m in Quarter 1 of 2001, making the R520m the first ever commercially available Bluetooth phone. In parallel, IBM introduced the IBM ThinkPad A30 in October 2001 which was the first notebook with integrated Bluetooth.
Bluetooth's early incorporation into consumer electronics products continued at Vosi Technologies in Costa Mesa, California, initially overseen by founding members Bejan Amini and Tom Davidson. Vosi Technologies had been created by real estate developer Ivano Stegmenga, with United States Patent 608507, for communication between a cellular phone and a vehicle's audio system. At the time, Sony/Ericsson had only a minor market share in the cellular phone market, which was dominated in the US by Nokia and Motorola. Due to ongoing negotiations for an intended licensing agreement with Motorola beginning in the late 1990s, Vosi could not publicly disclose the intention, integration, and initial development of other enabled devices which were to be the first "Smart Home" internet connected devices.
Vosi needed a means for the system to communicate without a wired connection from the vehicle to the other devices in the network. Bluetooth was chosen, since Wi-Fi was not yet readily available or supported in the public market. Vosi had begun to develop the Vosi Cello integrated vehicular system and some other internet connected devices, one of which was intended to be a table-top device named the Vosi Symphony, networked with Bluetooth. Through the negotiations with Motorola, Vosi introduced and disclosed its intent to integrate Bluetooth in its devices. In the early 2000s a legal battle ensued between Vosi and Motorola, which indefinitely suspended release of the devices. Later, Motorola implemented it in their devices which initiated the significant propagation of Bluetooth in the public market due to its large market share at the time.
In 2012, Jaap Haartsen was nominated by the European Patent Office for the European Inventor Award. | Bluetooth | Wikipedia | 464 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Implementation
Bluetooth operates at frequencies between 2.402 and 2.480GHz, or 2.400 and 2.4835GHz, including guard bands 2MHz wide at the bottom end and 3.5MHz wide at the top. This is in the globally unlicensed (but not unregulated) industrial, scientific and medical (ISM) 2.4GHz short-range radio frequency band. Bluetooth uses a radio technology called frequency-hopping spread spectrum. Bluetooth divides transmitted data into packets, and transmits each packet on one of 79 designated Bluetooth channels. Each channel has a bandwidth of 1MHz. It usually performs 1600hops per second, with adaptive frequency-hopping (AFH) enabled. Bluetooth Low Energy uses 2MHz spacing, which accommodates 40 channels.
Originally, Gaussian frequency-shift keying (GFSK) modulation was the only modulation scheme available. Since the introduction of Bluetooth 2.0+EDR, π/4-DQPSK (differential quadrature phase-shift keying) and 8-DPSK modulation may also be used between compatible devices. Devices functioning with GFSK are said to be operating in basic rate (BR) mode, where an instantaneous bit rate of 1Mbit/s is possible. The term Enhanced Data Rate (EDR) is used to describe π/4-DPSK (EDR2) and 8-DPSK (EDR3) schemes, transferring 2 and 3Mbit/s respectively.
In 2019, Apple published an extension called HDR which supports data rates of 4 (HDR4) and 8 (HDR8) Mbit/s using π/4-DQPSK modulation on 4 MHz channels with forward error correction (FEC). | Bluetooth | Wikipedia | 377 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Bluetooth is a packet-based protocol with a master/slave architecture. One master may communicate with up to seven slaves in a piconet. All devices within a given piconet use the clock provided by the master as the base for packet exchange. The master clock ticks with a period of 312.5μs, two clock ticks then make up a slot of 625μs, and two slots make up a slot pair of 1250μs. In the simple case of single-slot packets, the master transmits in even slots and receives in odd slots. The slave, conversely, receives in even slots and transmits in odd slots. Packets may be 1, 3, or 5 slots long, but in all cases, the master's transmission begins in even slots and the slave's in odd slots.
The above excludes Bluetooth Low Energy, introduced in the 4.0 specification, which uses the same spectrum but somewhat differently.
Communication and connection
A master BR/EDR Bluetooth device can communicate with a maximum of seven devices in a piconet (an ad hoc computer network using Bluetooth technology), though not all devices reach this maximum. The devices can switch roles, by agreement, and the slave can become the master (for example, a headset initiating a connection to a phone necessarily begins as master—as an initiator of the connection—but may subsequently operate as the slave).
The Bluetooth Core Specification provides for the connection of two or more piconets to form a scatternet, in which certain devices simultaneously play the master/leader role in one piconet and the slave role in another.
At any given time, data can be transferred between the master and one other device (except for the little-used broadcast mode). The master chooses which slave device to address; typically, it switches rapidly from one device to another in a round-robin fashion. Since it is the master that chooses which slave to address, whereas a slave is (in theory) supposed to listen in each receive slot, being a master is a lighter burden than being a slave. Being a master of seven slaves is possible; being a slave of more than one master is possible. The specification is vague as to required behavior in scatternets. | Bluetooth | Wikipedia | 464 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Uses
Bluetooth is a standard wire-replacement communications protocol primarily designed for low power consumption, with a short range based on low-cost transceiver microchips in each device. Because the devices use a radio (broadcast) communications system, they do not have to be in visual line of sight of each other; however, a quasi optical wireless path must be viable.
Bluetooth classes and power use
Historically, the Bluetooth range was defined by the radio class, with a lower class (and higher output power) having larger range. The actual range of a given link depends on several qualities of both communicating devices and the air and obstacles in between. The primary attributes affecting range are the data rate, protocol (Bluetooth Classic or Bluetooth Low Energy), transmission power, and receiver sensitivity, and the relative orientations and gains of both antennas.
The effective range varies depending on propagation conditions, material coverage, production sample variations, antenna configurations and battery conditions. Most Bluetooth applications are for indoor conditions, where attenuation of walls and signal fading due to signal reflections make the range far lower than specified line-of-sight ranges of the Bluetooth products.
Most Bluetooth applications are battery-powered Class 2 devices, with little difference in range whether the other end of the link is a Class 1 or Class 2 device as the lower-powered device tends to set the range limit. In some cases the effective range of the data link can be extended when a Class 2 device is connecting to a Class 1 transceiver with both higher sensitivity and transmission power than a typical Class 2 device. In general, however, Class 1 devices have sensitivities similar to those of Class 2 devices. Connecting two Class 1 devices with both high sensitivity and high power can allow ranges far in excess of the typical 100 m, depending on the throughput required by the application. Some such devices allow open field ranges of up to 1 km and beyond between two similar devices without exceeding legal emission limits.
Bluetooth profile
To use Bluetooth wireless technology, a device must be able to interpret certain Bluetooth profiles.
For example,
The Headset Profile (HSP) connects headphones and earbuds to a cell phone or laptop.
The Health Device Profile (HDP) can connect a cell phone to a digital thermometer or heart rate detector.
The Video Distribution Profile (VDP) sends a video stream from a video camera to a TV screen or a recording device. | Bluetooth | Wikipedia | 495 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Profiles are definitions of possible applications and specify general behaviors that Bluetooth-enabled devices use to communicate with other Bluetooth devices. These profiles include settings to parameterize and to control the communication from the start. Adherence to profiles saves the time for transmitting the parameters anew before the bi-directional link becomes effective. There are a wide range of Bluetooth profiles that describe many different types of applications or use cases for devices.
List of applications | Bluetooth | Wikipedia | 87 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Wireless control and communication between a mobile phone and a handsfree headset. This was one of the earliest applications to become popular.
Wireless control of audio and communication functions between a mobile phone and a Bluetooth compatible car stereo system (and sometimes between the SIM card and the car phone).
Wireless communication between a smartphone and a smart lock for unlocking doors.
Wireless control of and communication with iOS and Android device phones, tablets and portable wireless speakers.
Wireless Bluetooth headset and intercom. Idiomatically, a headset is sometimes called "a Bluetooth".
Wireless streaming of audio to headphones with or without communication capabilities.
Wireless streaming of data collected by Bluetooth-enabled fitness devices to phone or PC.
Wireless networking between PCs in a confined space and where little bandwidth is required.
Wireless communication with PC input and output devices, the most common being the mouse, keyboard and printer.
Transfer of files, contact details, calendar appointments, and reminders between devices with OBEX and sharing directories via FTP.
Triggering the camera shutter of a smartphone using a Bluetooth controlled selfie stick.
Replacement of previous wired RS-232 serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.
For controls where infrared was often used.
For low bandwidth applications where higher USB bandwidth is not required and cable-free connection desired.
Sending small advertisements from Bluetooth-enabled advertising hoardings to other, discoverable, Bluetooth devices.
Wireless bridge between two Industrial Ethernet (e.g., PROFINET) networks.
Game consoles have been using Bluetooth as a wireless communications protocol for peripherals since the seventh generation, including Nintendo's Wii and Sony's PlayStation 3 which use Bluetooth for their respective controllers.
Dial-up internet access on personal computers or PDAs using a data-capable mobile phone as a wireless modem.
Short-range transmission of health sensor data from medical devices to mobile phone, set-top box or dedicated telehealth devices.
Allowing a DECT phone to ring and answer calls on behalf of a nearby mobile phone.
Real-time location systems (RTLS) are used to track and identify the location of objects in real time using "Nodes" or "tags" attached to, or embedded in, the objects tracked, and "Readers" that receive and process the wireless signals from these tags to determine their locations. | Bluetooth | Wikipedia | 487 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Personal security application on mobile phones for prevention of theft or loss of items. The protected item has a Bluetooth marker (e.g., a tag) that is in constant communication with the phone. If the connection is broken (the marker is out of range of the phone) then an alarm is raised. This can also be used as a man overboard alarm.
Calgary, Alberta, Canada's Roads Traffic division uses data collected from travelers' Bluetooth devices to predict travel times and road congestion for motorists.
Wireless transmission of audio (a more reliable alternative to FM transmitters)
Live video streaming to the visual cortical implant device by Nabeel Fattah in Newcastle university 2017.
Connection of motion controllers to a PC when using VR headsets
Wireless connection between TVs and soundbars. | Bluetooth | Wikipedia | 162 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Devices
Bluetooth exists in numerous products such as telephones, speakers, tablets, media players, robotics systems, laptops, and game console equipment as well as some high definition headsets, modems, hearing aids and even watches. Bluetooth is useful when transferring information between two or more devices that are near each other in low-bandwidth situations. Bluetooth is commonly used to transfer sound data with telephones (i.e., with a Bluetooth headset) or byte data with hand-held computers (transferring files).
Bluetooth protocols simplify the discovery and setup of services between devices. Bluetooth devices can advertise all of the services they provide. This makes using services easier, because more of the security, network address and permission configuration can be automated than with many other network types.
Computer requirements
A personal computer that does not have embedded Bluetooth can use a Bluetooth adapter that enables the PC to communicate with Bluetooth devices. While some desktop computers and most recent laptops come with a built-in Bluetooth radio, others require an external adapter, typically in the form of a small USB "dongle".
Unlike its predecessor, IrDA, which requires a separate adapter for each device, Bluetooth lets multiple devices communicate with a computer over a single adapter.
Operating system implementation | Bluetooth | Wikipedia | 267 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
For Microsoft platforms, Windows XP Service Pack 2 and SP3 releases work natively with Bluetooth v1.1, v2.0 and v2.0+EDR. Previous versions required users to install their Bluetooth adapter's own drivers, which were not directly supported by Microsoft. Microsoft's own Bluetooth dongles (packaged with their Bluetooth computer devices) have no external drivers and thus require at least Windows XP Service Pack 2. Windows Vista RTM/SP1 with the Feature Pack for Wireless or Windows Vista SP2 work with Bluetooth v2.1+EDR. Windows 7 works with Bluetooth v2.1+EDR and Extended Inquiry Response (EIR).
The Windows XP and Windows Vista/Windows 7 Bluetooth stacks support the following Bluetooth profiles natively: PAN, SPP, DUN, HID, HCRP. The Windows XP stack can be replaced by a third party stack that supports more profiles or newer Bluetooth versions. The Windows Vista/Windows 7 Bluetooth stack supports vendor-supplied additional profiles without requiring that the Microsoft stack be replaced. Windows 8 and later support Bluetooth Low Energy (BLE). It is generally recommended to install the latest vendor driver and its associated stack to be able to use the Bluetooth device at its fullest extent.
Apple products have worked with Bluetooth since Mac OSX v10.2, which was released in 2002.
Linux has two popular Bluetooth stacks, BlueZ and Fluoride. The BlueZ stack is included with most Linux kernels and was originally developed by Qualcomm. Fluoride, earlier known as Bluedroid is included in Android OS and was originally developed by Broadcom.
There is also Affix stack, developed by Nokia. It was once popular, but has not been updated since 2005.
FreeBSD has included Bluetooth since its v5.0 release, implemented through netgraph.
NetBSD has included Bluetooth since its v4.0 release. Its Bluetooth stack was ported to OpenBSD as well, however OpenBSD later removed it as unmaintained.
DragonFly BSD has had NetBSD's Bluetooth implementation since 1.11 (2008). A netgraph-based implementation from FreeBSD has also been available in the tree, possibly disabled until 2014-11-15, and may require more work. | Bluetooth | Wikipedia | 487 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Specifications and features
The specifications were formalized by the Bluetooth Special Interest Group (SIG) and formally announced on 20 May 1998. In 2014 it had a membership of over 30,000 companies worldwide. It was established by Ericsson, IBM, Intel, Nokia and Toshiba, and later joined by many other companies.
All versions of the Bluetooth standards are backward-compatible with all earlier versions.
The Bluetooth Core Specification Working Group (CSWG) produces mainly four kinds of specifications:
The Bluetooth Core Specificationtypically released every few years
Core Specification Addendum (CSA)
Core Specification Supplements (CSS)can be released more frequently than Addenda
Errataavailable with a Bluetooth SIG account: Errata login)
Bluetooth 1.0 and 1.0B
Products were not interoperable.
Anonymity was not possible, preventing certain services from using Bluetooth environments.
Bluetooth 1.1
Ratified as IEEE Standard 802.15.1–2002
Many errors found in the v1.0B specifications were fixed.
Added possibility of non-encrypted channels.
Received signal strength indicator (RSSI)
Bluetooth 1.2
Major enhancements include:
Faster connection and discovery
Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence
Higher transmission speeds in practice than in v1.1, up to 721 kbit/s
Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets, and may optionally increase audio latency to provide better concurrent data transfer
Host Controller Interface (HCI) operation with three-wire UART
Ratified as IEEE Standard 802.15.1–2005
Introduced flow control and retransmission modes for
Bluetooth 2.0 + EDR
This version of the Bluetooth Core Specification was released before 2005. The main difference is the introduction of an Enhanced Data Rate (EDR) for faster data transfer. The data rate of EDR is 3Mbit/s, although the maximum data transfer rate (allowing for inter-packet time and acknowledgements) is 2.1Mbit/s. EDR uses a combination of GFSK and phase-shift keying modulation (PSK) with two variants, π/4-DQPSK and 8-DPSK. EDR can provide a lower power consumption through a reduced duty cycle. | Bluetooth | Wikipedia | 506 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
The specification is published as Bluetooth v2.0 + EDR, which implies that EDR is an optional feature. Aside from EDR, the v2.0 specification contains other minor improvements, and products may claim compliance to "Bluetooth v2.0" without supporting the higher data rate. At least one commercial device states "Bluetooth v2.0 without EDR" on its data sheet.
Bluetooth 2.1 + EDR
Bluetooth Core Specification version 2.1 + EDR was adopted by the Bluetooth SIG on 26 July 2007.
The headline feature of v2.1 is secure simple pairing (SSP): this improves the pairing experience for Bluetooth devices, while increasing the use and strength of security.
Version 2.1 allows various other improvements, including extended inquiry response (EIR), which provides more information during the inquiry procedure to allow better filtering of devices before connection; and sniff subrating, which reduces the power consumption in low-power mode.
Bluetooth 3.0 + HS
Version 3.0 + HS of the Bluetooth Core Specification was adopted by the Bluetooth SIG on 21 April 2009. Bluetooth v3.0 + HS provides theoretical data transfer speeds of up to 24 Mbit/s, though not over the Bluetooth link itself. Instead, the Bluetooth link is used for negotiation and establishment, and the high data rate traffic is carried over a colocated 802.11 link.
The main new feature is (Alternative MAC/PHY), the addition of 802.11 as a high-speed transport. The high-speed part of the specification is not mandatory, and hence only devices that display the "+HS" logo actually support Bluetooth over 802.11 high-speed data transfer. A Bluetooth v3.0 device without the "+HS" suffix is only required to support features introduced in Core Specification version 3.0 or earlier Core Specification Addendum 1. | Bluetooth | Wikipedia | 399 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
L2CAP Enhanced modes Enhanced Retransmission Mode (ERTM) implements reliable L2CAP channel, while Streaming Mode (SM) implements unreliable channel with no retransmission or flow control. Introduced in Core Specification Addendum 1.
Alternative MAC/PHY Enables the use of alternative MAC and PHYs for transporting Bluetooth profile data. The Bluetooth radio is still used for device discovery, initial connection and profile configuration. However, when large quantities of data must be sent, the high-speed alternative MAC PHY 802.11 (typically associated with Wi-Fi) transports the data. This means that Bluetooth uses proven low power connection models when the system is idle, and the faster radio when it must send large quantities of data. AMP links require enhanced L2CAP modes.
Unicast Connectionless Data Permits sending service data without establishing an explicit L2CAP channel. It is intended for use by applications that require low latency between user action and reconnection/transmission of data. This is only appropriate for small amounts of data.
Enhanced Power Control Updates the power control feature to remove the open loop power control, and also to clarify ambiguities in power control introduced by the new modulation schemes added for EDR. Enhanced power control removes the ambiguities by specifying the behavior that is expected. The feature also adds closed loop power control, meaning RSSI filtering can start as the response is received. Additionally, a "go straight to maximum power" request has been introduced. This is expected to deal with the headset link loss issue typically observed when a user puts their phone into a pocket on the opposite side to the headset.
Ultra-wideband
The high-speed (AMP) feature of Bluetooth v3.0 was originally intended for UWB, but the WiMedia Alliance, the body responsible for the flavor of UWB intended for Bluetooth, announced in March 2009 that it was disbanding, and ultimately UWB was omitted from the Core v3.0 specification. | Bluetooth | Wikipedia | 414 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
On 16 March 2009, the WiMedia Alliance announced it was entering into technology transfer agreements for the WiMedia Ultra-wideband (UWB) specifications. WiMedia has transferred all current and future specifications, including work on future high-speed and power-optimized implementations, to the Bluetooth Special Interest Group (SIG), Wireless USB Promoter Group and the USB Implementers Forum. After successful completion of the technology transfer, marketing, and related administrative items, the WiMedia Alliance ceased operations.
In October 2009, the Bluetooth Special Interest Group suspended development of UWB as part of the alternative MAC/PHY, Bluetooth v3.0 + HS solution. A small, but significant, number of former WiMedia members had not and would not sign up to the necessary agreements for the IP transfer. As of 2009, the Bluetooth SIG was in the process of evaluating other options for its longer-term roadmap.
Bluetooth 4.0
The Bluetooth SIG completed the Bluetooth Core Specification version 4.0 (called Bluetooth Smart) and has been adopted . It includes Classic Bluetooth, Bluetooth high speed and Bluetooth Low Energy (BLE) protocols. Bluetooth high speed is based on Wi-Fi, and Classic Bluetooth consists of legacy Bluetooth protocols.
Bluetooth Low Energy, previously known as Wibree, is a subset of Bluetooth v4.0 with an entirely new protocol stack for rapid build-up of simple links. As an alternative to the Bluetooth standard protocols that were introduced in Bluetooth v1.0 to v3.0, it is aimed at very low power applications powered by a coin cell. Chip designs allow for two types of implementation, dual-mode, single-mode and enhanced past versions. The provisional names Wibree and Bluetooth ULP (Ultra Low Power) were abandoned and the BLE name was used for a while. In late 2011, new logos "Bluetooth Smart Ready" for hosts and "Bluetooth Smart" for sensors were introduced as the general-public face of BLE.
Compared to Classic Bluetooth, Bluetooth Low Energy is intended to provide considerably reduced power consumption and cost while maintaining a similar communication range. In terms of lengthening the battery life of Bluetooth devices, represents a significant progression. | Bluetooth | Wikipedia | 471 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
In a single-mode implementation, only the low energy protocol stack is implemented. Dialog Semiconductor, STMicroelectronics, AMICCOM, CSR, Nordic Semiconductor and Texas Instruments have released single mode Bluetooth Low Energy solutions.
In a dual-mode implementation, Bluetooth Smart functionality is integrated into an existing Classic Bluetooth controller. , the following semiconductor companies have announced the availability of chips meeting the standard: Qualcomm Atheros, CSR, Broadcom and Texas Instruments. The compliant architecture shares all of Classic Bluetooth's existing radio and functionality resulting in a negligible cost increase compared to Classic Bluetooth.
Cost-reduced single-mode chips, which enable highly integrated and compact devices, feature a lightweight Link Layer providing ultra-low power idle mode operation, simple device discovery, and reliable point-to-multipoint data transfer with advanced power-save and secure encrypted connections at the lowest possible cost.
General improvements in version 4.0 include the changes necessary to facilitate BLE modes, as well the Generic Attribute Profile (GATT) and Security Manager (SM) services with AES Encryption.
Core Specification Addendum 2 was unveiled in December 2011; it contains improvements to the audio Host Controller Interface and to the High Speed (802.11) Protocol Adaptation Layer.
Core Specification Addendum 3 revision 2 has an adoption date of 24 July 2012.
Core Specification Addendum 4 has an adoption date of 12 February 2013.
Bluetooth 4.1
The Bluetooth SIG announced formal adoption of the Bluetooth v4.1 specification on 4 December 2013. This specification is an incremental software update to Bluetooth Specification v4.0, and not a hardware update. The update incorporates Bluetooth Core Specification Addenda (CSA 1, 2, 3 & 4) and adds new features that improve consumer usability. These include increased co-existence support for LTE, bulk data exchange rates—and aid developer innovation by allowing devices to support multiple roles simultaneously.
New features of this specification include:
Mobile wireless service coexistence signaling
Train nudging and generalized interlaced scanning
Low Duty Cycle Directed Advertising
L2CAP connection-oriented and dedicated channels with credit-based flow control
Dual Mode and Topology
LE Link Layer Topology
802.11n PAL
Audio architecture updates for Wide Band Speech
Fast data advertising interval
Limited discovery time
Some features were already available in a Core Specification Addendum (CSA) before the release of v4.1. | Bluetooth | Wikipedia | 506 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Bluetooth 4.2
Released on 2 December 2014, it introduces features for the Internet of things.
The major areas of improvement are:
Bluetooth Low Energy Secure Connection with Data Packet Length Extension to improve the cryptographic protocol
Link Layer Privacy with Extended Scanner Filter Policies to improve data security
Internet Protocol Support Profile (IPSP) version 6 ready for Bluetooth smart devices to support the Internet of things and home automation
Older Bluetooth hardware may receive 4.2 features such as Data Packet Length Extension and improved privacy via firmware updates.
Bluetooth 5
The Bluetooth SIG released Bluetooth 5 on 6 December 2016. Its new features are mainly focused on new Internet of Things technology. Sony was the first to announce Bluetooth 5.0 support with its Xperia XZ Premium in Feb 2017 during the Mobile World Congress 2017. The Samsung Galaxy S8 launched with Bluetooth 5 support in April 2017. In September 2017, the iPhone 8, 8 Plus and iPhone X launched with Bluetooth 5 support as well. Apple also integrated Bluetooth 5 in its new HomePod offering released on 9 February 2018. Marketing drops the point number; so that it is just "Bluetooth 5" (unlike Bluetooth 4.0); the change is for the sake of "Simplifying our marketing, communicating user benefits more effectively and making it easier to signal significant technology updates to the market."
Bluetooth 5 provides, for BLE, options that can double the data rate (2Mbit/s burst) at the expense of range, or provide up to four times the range at the expense of data rate. The increase in transmissions could be important for Internet of Things devices, where many nodes connect throughout a whole house. Bluetooth 5 increases capacity of connectionless services such as location-relevant navigation of low-energy Bluetooth connections.
The major areas of improvement are:
Slot Availability Mask (SAM)
2 Mbit/s PHY for
LE Long Range
High Duty Cycle Non-Connectable Advertising
LE Advertising Extensions
LE Channel Selection Algorithm #2
Features added in CSA5 – integrated in v5.0:
Higher Output Power
The following features were removed in this version of the specification:
Park State
Bluetooth 5.1
The Bluetooth SIG presented Bluetooth 5.1 on 21 January 2019. | Bluetooth | Wikipedia | 458 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
The major areas of improvement are:
Angle of arrival (AoA) and Angle of Departure (AoD) which are used for locating and tracking of devices
Advertising Channel Index
GATT caching
Minor Enhancements batch 1:
HCI support for debug keys in LE Secure Connections
Sleep clock accuracy update mechanism
ADI field in scan response data
Interaction between and Flow Specification
Block Host channel classification for secondary advertising
Allow the SID to appear in scan response reports
Specify the behavior when rules are violated
Periodic Advertising Sync Transfer
Features added in Core Specification Addendum (CSA) 6 – integrated in v5.1:
Models
Mesh-based model hierarchy
The following features were removed in this version of the specification:
Unit keys
Bluetooth 5.2
On 31 December 2019, the Bluetooth SIG published the Bluetooth Core Specification version 5.2. The new specification adds new features:
Enhanced Attribute Protocol (EATT), an improved version of the Attribute Protocol (ATT)
LE Power Control
LE Isochronous Channels
LE Audio that is built on top of the new 5.2 features. BT LE Audio was announced in January 2020 at CES by the Bluetooth SIG. Compared to regular Bluetooth Audio, Bluetooth Low Energy Audio makes lower battery consumption possible and creates a standardized way of transmitting audio over BT LE. Bluetooth LE Audio also allows one-to-many and many-to-one transmission, allowing multiple receivers from one source or one receiver for multiple sources, known as Auracast. It uses a new LC3 codec. BLE Audio will also add support for hearing aids. On 12 July 2022, the Bluetooth SIG announced the completion of Bluetooth LE Audio. The standard has a lower minimum latency claim of 20–30 ms vs Bluetooth Classic audio of 100–200 ms. At IFA in August 2023 Samsung announced support for Auracast through a software update for their Galaxy Buds2 Pro and two of their TV's. In October users started getting updates for the earbuds.
Bluetooth 5.3
The Bluetooth SIG published the Bluetooth Core Specification version 5.3 on 13 July 2021. The feature enhancements of Bluetooth 5.3 are:
Connection Subrating
Periodic Advertisement Interval
Channel Classification Enhancement
Encryption key size control enhancements
The following features were removed in this version of the specification:
Alternate MAC and PHY (AMP) Extension | Bluetooth | Wikipedia | 480 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Bluetooth 5.4
The Bluetooth SIG released the Bluetooth Core Specification version 5.4 on 7 February 2023. This new version adds the following features:
Periodic Advertising with Responses (PAwR)
Encrypted Advertising Data
LE Security Levels Characteristic
Advertising Coding Selection
Bluetooth 6.0
The Bluetooth SIG released the Bluetooth Core Specification version 6.0 on 27 August 2024. This version adds the following features:
Bluetooth Channel Sounding
Decision-based advertising filtering
Monitoring advertisers
enhancement
LL extended feature set
Frame space update
Technical information
Architecture
Software
Seeking to extend the compatibility of Bluetooth devices, the devices that adhere to the standard use an interface called HCI (Host Controller Interface) between the host and the controller.
High-level protocols such as the SDP (Protocol used to find other Bluetooth devices within the communication range, also responsible for detecting the function of devices in range), RFCOMM (Protocol used to emulate serial port connections) and TCS (Telephony control protocol) interact with the baseband controller through the L2CAP (Logical Link Control and Adaptation Protocol). The L2CAP protocol is responsible for the segmentation and reassembly of the packets.
Hardware
The hardware that makes up the Bluetooth device is made up of, logically, two parts; which may or may not be physically separate. A radio device, responsible for modulating and transmitting the signal; and a digital controller. The digital controller is likely a CPU, one of whose functions is to run a Link Controller; and interfaces with the host device; but some functions may be delegated to hardware. The Link Controller is responsible for the processing of the baseband and the management of ARQ and physical layer FEC protocols. In addition, it handles the transfer functions (both asynchronous and synchronous), audio coding (e.g. SBC (codec)) and data encryption. The CPU of the device is responsible for attending the instructions related to Bluetooth of the host device, in order to simplify its operation. To do this, the CPU runs software called Link Manager that has the function of communicating with other devices through the LMP protocol.
A Bluetooth device is a short-range wireless device. Bluetooth devices are fabricated on RF CMOS integrated circuit (RF circuit) chips.
Bluetooth protocol stack | Bluetooth | Wikipedia | 483 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Bluetooth is defined as a layer protocol architecture consisting of core protocols, cable replacement protocols, telephony control protocols, and adopted protocols. Mandatory protocols for all Bluetooth stacks are LMP, L2CAP and SDP. In addition, devices that communicate with Bluetooth almost universally can use these protocols: HCI and RFCOMM.
Link Manager
The Link Manager (LM) is the system that manages establishing the connection between devices. It is responsible for the establishment, authentication and configuration of the link. The Link Manager locates other managers and communicates with them via the management protocol of the LMP link. To perform its function as a service provider, the LM uses the services included in the Link Controller (LC).
The Link Manager Protocol basically consists of several PDUs (Protocol Data Units) that are sent from one device to another. The following is a list of supported services:
Transmission and reception of data.
Name request
Request of the link addresses.
Establishment of the connection.
Authentication.
Negotiation of link mode and connection establishment.
Host Controller Interface
The Host Controller Interface provides a command interface between the controller and the host.
Logical Link Control and Adaptation Protocol
The Logical Link Control and Adaptation Protocol (L2CAP) is used to multiplex multiple logical connections between two devices using different higher level protocols.
Provides segmentation and reassembly of on-air packets.
In Basic mode, L2CAP provides packets with a payload configurable up to 64 kB, with 672 bytes as the default MTU, and 48 bytes as the minimum mandatory supported MTU.
In Retransmission and Flow Control modes, L2CAP can be configured either for isochronous data or reliable data per channel by performing retransmissions and CRC checks.
Bluetooth Core Specification Addendum 1 adds two additional L2CAP modes to the core specification. These modes effectively deprecate original Retransmission and Flow Control modes:
Enhanced Retransmission Mode (ERTM) This mode is an improved version of the original retransmission mode. This mode provides a reliable L2CAP channel.
Streaming Mode (SM) This is a very simple mode, with no retransmission or flow control. This mode provides an unreliable L2CAP channel. | Bluetooth | Wikipedia | 463 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Reliability in any of these modes is optionally and/or additionally guaranteed by the lower layer Bluetooth BDR/EDR air interface by configuring the number of retransmissions and flush timeout (time after which the radio flushes packets). In-order sequencing is guaranteed by the lower layer.
Only L2CAP channels configured in ERTM or SM may be operated over AMP logical links.
Service Discovery Protocol
The Service Discovery Protocol (SDP) allows a device to discover services offered by other devices, and their associated parameters. For example, when you use a mobile phone with a Bluetooth headset, the phone uses SDP to determine which Bluetooth profiles the headset can use (Headset Profile, Hands Free Profile (HFP), Advanced Audio Distribution Profile (A2DP) etc.) and the protocol multiplexer settings needed for the phone to connect to the headset using each of them. Each service is identified by a Universally unique identifier (UUID), with official services (Bluetooth profiles) assigned a short form UUID (16 bits rather than the full 128).
Radio Frequency Communications
Radio Frequency Communications (RFCOMM) is a cable replacement protocol used for generating a virtual serial data stream. RFCOMM provides for binary data transport and emulates EIA-232 (formerly RS-232) control signals over the Bluetooth baseband layer, i.e., it is a serial port emulation.
RFCOMM provides a simple, reliable, data stream to the user, similar to TCP. It is used directly by many telephony related profiles as a carrier for AT commands, as well as being a transport layer for OBEX over Bluetooth.
Many Bluetooth applications use RFCOMM because of its widespread support and publicly available API on most operating systems. Additionally, applications that used a serial port to communicate can be quickly ported to use RFCOMM.
Bluetooth Network Encapsulation Protocol
The Bluetooth Network Encapsulation Protocol (BNEP) is used for transferring another protocol stack's data via an L2CAP channel.
Its main purpose is the transmission of IP packets in the Personal Area Networking Profile.
BNEP performs a similar function to SNAP in Wireless LAN. | Bluetooth | Wikipedia | 459 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Audio/Video Control Transport Protocol
The Audio/Video Control Transport Protocol (AVCTP) is used by the remote control profile to transfer AV/C commands over an L2CAP channel. The music control buttons on a stereo headset use this protocol to control the music player.
Audio/Video Distribution Transport Protocol
The Audio/Video Distribution Transport Protocol (AVDTP) is used by the advanced audio distribution (A2DP) profile to stream music to stereo headsets over an L2CAP channel intended for video distribution profile in the Bluetooth transmission.
Telephony Control Protocol
The Telephony Control Protocol– Binary (TCS BIN) is the bit-oriented protocol that defines the call control signaling for the establishment of voice and data calls between Bluetooth devices. Additionally, "TCS BIN defines mobility management procedures for handling groups of Bluetooth TCS devices."
TCS-BIN is only used by the cordless telephony profile, which failed to attract implementers. As such it is only of historical interest.
Adopted protocols
Adopted protocols are defined by other standards-making organizations and incorporated into Bluetooth's protocol stack, allowing Bluetooth to code protocols only when necessary. The adopted protocols include:
Point-to-Point Protocol (PPP) Internet standard protocol for transporting IP datagrams over a point-to-point link.
TCP/IP/UDP Foundation Protocols for TCP/IP protocol suite
Object Exchange Protocol (OBEX) Session-layer protocol for the exchange of objects, providing a model for object and operation representation
Wireless Application Environment/Wireless Application Protocol (WAE/WAP) WAE specifies an application framework for wireless devices and WAP is an open standard to provide mobile users access to telephony and information services.
Baseband error correction
Depending on packet type, individual packets may be protected by error correction, either 1/3 rate forward error correction (FEC) or 2/3 rate. In addition, packets with CRC will be retransmitted until acknowledged by automatic repeat request (ARQ).
Setting up connections
Any Bluetooth device in discoverable mode transmits the following information on demand:
Device name
Device class
List of services
Technical information (for example: device features, manufacturer, Bluetooth specification used, clock offset) | Bluetooth | Wikipedia | 461 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Any device may perform an inquiry to find other devices to connect to, and any device can be configured to respond to such inquiries. However, if the device trying to connect knows the address of the device, it always responds to direct connection requests and transmits the information shown in the list above if requested. Use of a device's services may require pairing or acceptance by its owner, but the connection itself can be initiated by any device and held until it goes out of range. Some devices can be connected to only one device at a time, and connecting to them prevents them from connecting to other devices and appearing in inquiries until they disconnect from the other device.
Every device has a unique 48-bit address. However, these addresses are generally not shown in inquiries. Instead, friendly Bluetooth names are used, which can be set by the user. This name appears when another user scans for devices and in lists of paired devices.
Most cellular phones have the Bluetooth name set to the manufacturer and model of the phone by default. Most cellular phones and laptops show only the Bluetooth names and special programs are required to get additional information about remote devices. This can be confusing as, for example, there could be several cellular phones in range named T610 (see Bluejacking).
Pairing and bonding
Motivation
Many services offered over Bluetooth can expose private data or let a connecting party control the Bluetooth device. Security reasons make it necessary to recognize specific devices, and thus enable control over which devices can connect to a given Bluetooth device. At the same time, it is useful for Bluetooth devices to be able to establish a connection without user intervention (for example, as soon as in range).
To resolve this conflict, Bluetooth uses a process called bonding, and a bond is generated through a process called pairing. The pairing process is triggered either by a specific request from a user to generate a bond (for example, the user explicitly requests to "Add a Bluetooth device"), or it is triggered automatically when connecting to a service where (for the first time) the identity of a device is required for security purposes. These two cases are referred to as dedicated bonding and general bonding respectively.
Pairing often involves some level of user interaction. This user interaction confirms the identity of the devices. When pairing completes, a bond forms between the two devices, enabling those two devices to connect in the future without repeating the pairing process to confirm device identities. When desired, the user can remove the bonding relationship. | Bluetooth | Wikipedia | 507 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Implementation
During pairing, the two devices establish a relationship by creating a shared secret known as a link key. If both devices store the same link key, they are said to be paired or bonded. A device that wants to communicate only with a bonded device can cryptographically authenticate the identity of the other device, ensuring it is the same device it previously paired with. Once a link key is generated, an authenticated ACL link between the devices may be encrypted to protect exchanged data against eavesdropping. Users can delete link keys from either device, which removes the bond between the devices—so it is possible for one device to have a stored link key for a device it is no longer paired with.
Bluetooth services generally require either encryption or authentication and as such require pairing before they let a remote device connect. Some services, such as the Object Push Profile, elect not to explicitly require authentication or encryption so that pairing does not interfere with the user experience associated with the service use-cases. | Bluetooth | Wikipedia | 205 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Pairing mechanisms
Pairing mechanisms changed significantly with the introduction of Secure Simple Pairing in Bluetooth v2.1. The following summarizes the pairing mechanisms:
Legacy pairing: This is the only method available in Bluetooth v2.0 and before. Each device must enter a PIN code; pairing is only successful if both devices enter the same PIN code. Any 16-byte UTF-8 string may be used as a PIN code; however, not all devices may be capable of entering all possible PIN codes.
Limited input devices: The obvious example of this class of device is a Bluetooth Hands-free headset, which generally have few inputs. These devices usually have a fixed PIN, for example "0000" or "1234", that are hard-coded into the device.
Numeric input devices: Mobile phones are classic examples of these devices. They allow a user to enter a numeric value up to 16 digits in length.
Alpha-numeric input devices: PCs and smartphones are examples of these devices. They allow a user to enter full UTF-8 text as a PIN code. If pairing with a less capable device the user must be aware of the input limitations on the other device; there is no mechanism available for a capable device to determine how it should limit the available input a user may use.
Secure Simple Pairing (SSP): This is required by Bluetooth v2.1, although a Bluetooth v2.1 device may only use legacy pairing to interoperate with a v2.0 or earlier device. Secure Simple Pairing uses a form of public-key cryptography, and some types can help protect against man in the middle, or MITM attacks. SSP has the following authentication mechanisms:
Just works: As the name implies, this method just works, with no user interaction. However, a device may prompt the user to confirm the pairing process. This method is typically used by headsets with minimal IO capabilities, and is more secure than the fixed PIN mechanism this limited set of devices uses for legacy pairing. This method provides no man-in-the-middle (MITM) protection. | Bluetooth | Wikipedia | 434 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Numeric comparison: If both devices have a display, and at least one can accept a binary yes/no user input, they may use Numeric Comparison. This method displays a 6-digit numeric code on each device. The user should compare the numbers to ensure they are identical. If the comparison succeeds, the user(s) should confirm pairing on the device(s) that can accept an input. This method provides MITM protection, assuming the user confirms on both devices and actually performs the comparison properly.
Passkey Entry: This method may be used between a device with a display and a device with numeric keypad entry (such as a keyboard), or two devices with numeric keypad entry. In the first case, the display presents a 6-digit numeric code to the user, who then enters the code on the keypad. In the second case, the user of each device enters the same 6-digit number. Both of these cases provide MITM protection.
Out of band (OOB): This method uses an external means of communication, such as near-field communication (NFC) to exchange some information used in the pairing process. Pairing is completed using the Bluetooth radio, but requires information from the OOB mechanism. This provides only the level of MITM protection that is present in the OOB mechanism. | Bluetooth | Wikipedia | 273 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
SSP is considered simple for the following reasons:
In most cases, it does not require a user to generate a passkey.
For use cases not requiring MITM protection, user interaction can be eliminated.
For numeric comparison, MITM protection can be achieved with a simple equality comparison by the user.
Using OOB with NFC enables pairing when devices simply get close, rather than requiring a lengthy discovery process.
Security concerns
Prior to Bluetooth v2.1, encryption is not required and can be turned off at any time. Moreover, the encryption key is only good for approximately 23.5 hours; using a single encryption key longer than this time allows simple XOR attacks to retrieve the encryption key.
Turning off encryption is required for several normal operations, so it is problematic to detect if encryption is disabled for a valid reason or a security attack.
Bluetooth v2.1 addresses this in the following ways:
Encryption is required for all non-SDP (Service Discovery Protocol) connections
A new Encryption Pause and Resume feature is used for all normal operations that require that encryption be disabled. This enables easy identification of normal operation from security attacks.
The encryption key must be refreshed before it expires.
Link keys may be stored on the device file system, not on the Bluetooth chip itself. Many Bluetooth chip manufacturers let link keys be stored on the device—however, if the device is removable, this means that the link key moves with the device.
Security
Overview
Bluetooth implements confidentiality, authentication and key derivation with custom algorithms based on the SAFER+ block cipher. Bluetooth key generation is generally based on a Bluetooth PIN, which must be entered into both devices. This procedure might be modified if one of the devices has a fixed PIN (e.g., for headsets or similar devices with a restricted user interface). During pairing, an initialization key or master key is generated, using the E22 algorithm.
The E0 stream cipher is used for encrypting packets, granting confidentiality, and is based on a shared cryptographic secret, namely a previously generated link key or master key. Those keys, used for subsequent encryption of data sent via the air interface, rely on the Bluetooth PIN, which has been entered into one or both devices.
An overview of Bluetooth vulnerabilities exploits was published in 2007 by Andreas Becker. | Bluetooth | Wikipedia | 480 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
In September 2008, the National Institute of Standards and Technology (NIST) published a Guide to Bluetooth Security as a reference for organizations. It describes Bluetooth security capabilities and how to secure Bluetooth technologies effectively. While Bluetooth has its benefits, it is susceptible to denial-of-service attacks, eavesdropping, man-in-the-middle attacks, message modification, and resource misappropriation. Users and organizations must evaluate their acceptable level of risk and incorporate security into the lifecycle of Bluetooth devices. To help mitigate risks, included in the NIST document are security checklists with guidelines and recommendations for creating and maintaining secure Bluetooth piconets, headsets, and smart card readers.
Bluetooth v2.1 – finalized in 2007 with consumer devices first appearing in 2009 – makes significant changes to Bluetooth's security, including pairing. See the pairing mechanisms section for more about these changes.
Bluejacking
Bluejacking is the sending of either a picture or a message from one user to an unsuspecting user through Bluetooth wireless technology. Common applications include short messages, e.g., "You've just been bluejacked!" Bluejacking does not involve the removal or alteration of any data from the device.
Some form of DoS is also possible, even in modern devices, by sending unsolicited pairing requests in rapid succession; this becomes disruptive because most systems display a full screen notification for every connection request, interrupting every other activity, especially on less powerful devices.
History of security concerns | Bluetooth | Wikipedia | 315 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
2001–2004
In 2001, Jakobsson and Wetzel from Bell Laboratories discovered flaws in the Bluetooth pairing protocol and also pointed to vulnerabilities in the encryption scheme. In 2003, Ben and Adam Laurie from A.L. Digital Ltd. discovered that serious flaws in some poor implementations of Bluetooth security may lead to disclosure of personal data. In a subsequent experiment, Martin Herfurt from the trifinite.group was able to do a field-trial at the CeBIT fairgrounds, showing the importance of the problem to the world. A new attack called BlueBug was used for this experiment. In 2004 the first purported virus using Bluetooth to spread itself among mobile phones appeared on the Symbian OS.
The virus was first described by Kaspersky Lab and requires users to confirm the installation of unknown software before it can propagate. The virus was written as a proof-of-concept by a group of virus writers known as "29A" and sent to anti-virus groups. Thus, it should be regarded as a potential (but not real) security threat to Bluetooth technology or Symbian OS since the virus has never spread outside of this system. In August 2004, a world-record-setting experiment (see also Bluetooth sniping) showed that the range of Class 2 Bluetooth radios could be extended to with directional antennas and signal amplifiers.
This poses a potential security threat because it enables attackers to access vulnerable Bluetooth devices from a distance beyond expectation. The attacker must also be able to receive information from the victim to set up a connection. No attack can be made against a Bluetooth device unless the attacker knows its Bluetooth address and which channels to transmit on, although these can be deduced within a few minutes if the device is in use.
2005
In January 2005, a mobile malware worm known as Lasco surfaced. The worm began targeting mobile phones using Symbian OS (Series 60 platform) using Bluetooth enabled devices to replicate itself and spread to other devices. The worm is self-installing and begins once the mobile user approves the transfer of the file (Velasco.sis) from another device. Once installed, the worm begins looking for other Bluetooth enabled devices to infect. Additionally, the worm infects other .SIS files on the device, allowing replication to another device through the use of removable media (Secure Digital, CompactFlash, etc.). The worm can render the mobile device unstable. | Bluetooth | Wikipedia | 504 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
In April 2005, University of Cambridge security researchers published results of their actual implementation of passive attacks against the PIN-based pairing between commercial Bluetooth devices. They confirmed that attacks are practicably fast, and the Bluetooth symmetric key establishment method is vulnerable. To rectify this vulnerability, they designed an implementation that showed that stronger, asymmetric key establishment is feasible for certain classes of devices, such as mobile phones.
In June 2005, Yaniv Shaked and Avishai Wool published a paper describing both passive and active methods for obtaining the PIN for a Bluetooth link. The passive attack allows a suitably equipped attacker to eavesdrop on communications and spoof if the attacker was present at the time of initial pairing. The active method makes use of a specially constructed message that must be inserted at a specific point in the protocol, to make the master and slave repeat the pairing process. After that, the first method can be used to crack the PIN. This attack's major weakness is that it requires the user of the devices under attack to re-enter the PIN during the attack when the device prompts them to. Also, this active attack probably requires custom hardware, since most commercially available Bluetooth devices are not capable of the timing necessary.
In August 2005, police in Cambridgeshire, England, issued warnings about thieves using Bluetooth enabled phones to track other devices left in cars. Police are advising users to ensure that any mobile networking connections are de-activated if laptops and other devices are left in this way.
2006
In April 2006, researchers from Secure Network and F-Secure published a report that warns of the large number of devices left in a visible state, and issued statistics on the spread of various Bluetooth services and the ease of spread of an eventual Bluetooth worm.
In October 2006, at the Luxembourgish Hack.lu Security Conference, Kevin Finistere and Thierry Zoller demonstrated and released a remote root shell via Bluetooth on Mac OS X v10.3.9 and v10.4. They also demonstrated the first Bluetooth PIN and Linkkeys cracker, which is based on the research of Wool and Shaked. | Bluetooth | Wikipedia | 435 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
2017
In April 2017, security researchers at Armis discovered multiple exploits in the Bluetooth software in various platforms, including Microsoft Windows, Linux, Apple iOS, and Google Android. These vulnerabilities are collectively called "BlueBorne". The exploits allow an attacker to connect to devices or systems without authentication and can give them "virtually full control over the device". Armis contacted Google, Microsoft, Apple, Samsung and Linux developers allowing them to patch their software before the coordinated announcement of the vulnerabilities on 12 September 2017.
2018
In July 2018, Lior Neumann and Eli Biham, researchers at the Technion – Israel Institute of Technology identified a security vulnerability in the latest Bluetooth pairing procedures: Secure Simple Pairing and LE Secure Connections.
Also, in October 2018, Karim Lounis, a network security researcher at Queen's University, identified a security vulnerability, called CDV (Connection Dumping Vulnerability), on various Bluetooth devices that allows an attacker to tear down an existing Bluetooth connection and cause the deauthentication and disconnection of the involved devices. The researcher demonstrated the attack on various devices of different categories and from different manufacturers.
2019
In August 2019, security researchers at the Singapore University of Technology and Design, Helmholtz Center for Information Security, and University of Oxford discovered a vulnerability, called KNOB (Key Negotiation of Bluetooth) in the key negotiation that would "brute force the negotiated encryption keys, decrypt the eavesdropped ciphertext, and inject valid encrypted messages (in real-time)".
Google released an Android security patch on 5 August 2019, which removed this vulnerability.
2023
In November 2023, researchers from Eurecom revealed a new class of attacks known as BLUFFS (Bluetooth Low Energy Forward and Future Secrecy Attacks). These 6 new attacks expand on and work in conjunction with the previously known KNOB and BIAS (Bluetooth Impersonation AttackS) attacks. While the previous KNOB and BIAS attacks allowed an attacker to decrypt and spoof Bluetooth packets within a session, BLUFFS extends this capability to all sessions generated by a device (including past, present, and future). All devices running Bluetooth versions 4.2 up to and including 5.4 are affected.
Health concerns | Bluetooth | Wikipedia | 462 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Bluetooth uses the radio frequency spectrum in the 2.402GHz to 2.480GHz range, which is non-ionizing radiation, of similar bandwidth to that used by wireless and mobile phones. No specific harm has been demonstrated, even though wireless transmission has been included by IARC in the possible carcinogen list. Maximum power output from a Bluetooth radio is 100mW for Class1, 2.5mW for Class2, and 1mW for Class3 devices. Even the maximum power output of Class1 is a lower level than the lowest-powered mobile phones. UMTS and W-CDMA output 250mW, GSM1800/1900 outputs 1000mW, and GSM850/900 outputs 2000mW.
Award programs
The Bluetooth Innovation World Cup, a marketing initiative of the Bluetooth Special Interest Group (SIG), was an international competition that encouraged the development of innovations for applications leveraging Bluetooth technology in sports, fitness and health care products. The competition aimed to stimulate new markets.
The Bluetooth Innovation World Cup morphed into the Bluetooth Breakthrough Awards in 2013. Bluetooth SIG subsequently launched the Imagine Blue Award in 2016 at Bluetooth World. The Bluetooth Breakthrough Awards program highlights the most innovative products and applications available today, prototypes coming soon, and student-led projects in the making. | Bluetooth | Wikipedia | 278 | 3742 | https://en.wikipedia.org/wiki/Bluetooth | Technology | Networks | null |
Boron is a chemical element. It has the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three valence electrons for forming covalent bonds, resulting in many compounds such as boric acid, the mineral sodium borate, and the ultra-hard crystals of boron carbide and boron nitride.
Boron is synthesized entirely by cosmic ray spallation and supernovas and not by stellar nucleosynthesis, so it is a low-abundance element in the Solar System and in the Earth's crust. It constitutes about 0.001 percent by weight of Earth's crust. It is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. These are mined industrially as evaporites, such as borax and kernite. The largest known deposits are in Turkey, the largest producer of boron minerals.
Elemental boron is found in small amounts in meteoroids, but chemically uncombined boron is not otherwise found naturally on Earth.
Several allotropes exist: amorphous boron is a brown powder; crystalline boron is silvery to black, extremely hard (9.3 on the Mohs scale), and a poor electrical conductor at room temperature (1.5 × 10−6 Ω−1 cm−1 room temperature electrical conductivity). The primary use of the element itself is as boron filaments with applications similar to carbon fibers in some high-strength materials.
Boron is primarily used in chemical compounds. About half of all production consumed globally is an additive in fiberglass for insulation and structural materials. The next leading use is in polymers and ceramics in high-strength, lightweight structural and heat-resistant materials. Borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. As sodium perborate, it is used as a bleach. A small amount is used as a dopant in semiconductors, and reagent intermediates in the synthesis of organic fine chemicals. A few boron-containing organic pharmaceuticals are used or are in study. Natural boron is composed of two stable isotopes, one of which (boron-10) has a number of uses as a neutron-capturing agent. | Boron | Wikipedia | 502 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
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