Scientists are also considering the use of magnetoencephalography (MEG) in future studies. This technology would link the spatial activation processes with the temporal patterns of brain response more accurately than simultaneously considering the response data from ERP and fMRI which are more limited.


Not only have studies suggested that the executive functioning of bilingualism extends beyond the language system, but bilinguals have also been shown to be faster processors who display fewer conflict effects than monolinguals in attentional tasks This research implies that there may be some spillover effects of learning a second language on other areas of cognitive function that could be explored.


One future direction theories on bilingual word recognition should take is the investigation of developmental aspects of bilingual lexical access. Most studies have investigated highly proficient bilinguals, but not many have looked at low-proficient bilinguals or even L2 learners. This new direction should prove to bring a lot of educational applications.


Expressive aphasia, also known as Broca's aphasia, is a type of aphasia characterized by partial loss of the ability to produce language (spoken, manual, or written), although comprehension generally remains intact. A person with expressive aphasia will exhibit effortful speech. Speech generally includes important content words but leaves out function words that have more grammatical significance than physical meaning, such as prepositions and articles. This is known as "telegraphic speech". The person's intended message may still be understood, but their sentence will not be grammatically correct. In very severe forms of expressive aphasia, a person may only speak using single word utterances. Typically, comprehension is mildly to moderately impaired in expressive aphasia due to difficulty understanding complex grammar.


It is caused by acquired damage to the anterior regions of the brain, such as Broca's area. It is one subset of a larger family of disorders known collectively as aphasia. Expressive aphasia contrasts with receptive aphasia, in which patients are able to speak in grammatical sentences that lack semantic significance and generally also have trouble with comprehension. Expressive aphasia differs from dysarthria, which is typified by a patient's inability to properly move the muscles of the tongue and mouth to produce speech. Expressive aphasia also differs from apraxia of speech, which is a motor disorder characterized by an inability to create and sequence motor plans for speech.


Broca's (expressive) aphasia is a type of non-fluent aphasia in which an individual's speech is halting and effortful. Misarticulations or distortions of consonants and vowels, namely phonetic dissolution, are common. Individuals with expressive aphasia may only produce single words, or words in groups of two or three. Long pauses between words are common and multi-syllabic words may be produced one syllable at a time with pauses between each syllable. The prosody of a person with Broca's aphasia is compromised by shortened length of utterances and the presence of self-repairs and disfluencies. Intonation and stress patterns are also deficient.


Self-monitoring is typically well preserved in patients with Broca's aphasia. They are usually aware of their communication deficits, and are more prone to depression and outbursts from frustration than are patients with other forms of aphasia.[7]


In general, word comprehension is preserved, allowing patients to have functional receptive language skills. Individuals with Broca's aphasia understand most of the everyday conversation around them, but higher-level deficits in receptive language can occur. Because comprehension is substantially impaired for more complex sentences, it is better to use simple language when speaking with an individual with expressive aphasia. This is exemplified by the difficulty to understand phrases or sentences with unusual structure. A typical patient with Broca's aphasia will misinterpret "the man is bitten by the dog" by switching the subject and object to “the dog is bitten by the man.”


Typically, people with expressive aphasia can understand speech and read better than they can produce speech and write. The person's writing will resemble their speech and will be effortful, lacking cohesion, and containing mostly content words. Letters will likely be formed clumsily and distorted and some may even be omitted. Although listening and reading are generally intact, subtle deficits in both reading and listening comprehension are almost always present during assessment of aphasia.


Because Broca's area is anterior to the primary motor cortex, which is responsible for movement of the face, hands, and arms, a lesion affecting Broca's areas may also result in hemiparesis (weakness of both limbs on the same side of the body) or hemiplegia (paralysis of both limbs on the same side of the body). The brain is wired contralaterally, which means the limbs on right side of the body are controlled by the left hemisphere and vice versa. Therefore, when Broca's area or surrounding areas in the left hemisphere are damaged, hemiplegia or hemiparesis often occurs on the right side of the body in individuals with Broca's aphasia.


Severity of expressive aphasia varies among patients. Some people may only have mild deficits and detecting problems with their language may be difficult. In the most extreme cases, patients may be able to produce only a single word. Even in such cases, over-learned and rote-learned speech patterns may be retained– for instance, some patients can count from one to ten, but cannot produce the same numbers in novel conversation.


In addition to difficulty expressing oneself, individuals with expressive aphasia are also noted to commonly have trouble with comprehension in certain linguistic areas. This agrammatism overlaps with receptive aphasia, but can be seen in patients who have expressive aphasia without being diagnosed as having receptive aphasia. The most well-noted of these are object-relative clauses, object Wh- questions, and topicalized structures (placing the topic at the beginning of the sentence). These three concepts all share phrasal movement, which can cause words to lose their thematic roles when they change order in the sentence. This is often not an issue for people without agrammatic aphasias, but many people with aphasia rely heavily on word order to understand roles that words play within the sentence.


The most common cause of expressive aphasia is stroke. A stroke is caused by hypoperfusion (lack of oxygen) to an area of the brain, which is commonly caused by thrombosis or embolism. Some form of aphasia occurs in 34 to 38% of stroke patients. Expressive aphasia occurs in approximately 12% of new cases of aphasia caused by stroke.


In most cases, expressive aphasia is caused by a stroke in Broca's area or the surrounding vicinity. Broca's area is in the lower part of the premotor cortex in the language dominant hemisphere and is responsible for planning motor speech movements. However, cases of expressive aphasia have been seen in patients with strokes in other areas of the brain. Patients with classic symptoms of expressive aphasia in general have more acute brain lesions, whereas patients with larger, widespread lesions exhibit a variety of symptoms that may be classified as global aphasia or left unclassified.


Expressive aphasia can also be caused by trauma to the brain, tumor, cerebral hemorrhage and by extradural abscess.


Understanding lateralization of brain function is important for understanding which areas of the brain cause expressive aphasia when damaged. In the past, it has been believed that the area for language production differs between left and right-handed individuals. If this were true, damage to the homologous region of Broca's area in the right hemisphere should cause aphasia in a left-handed individual. More recent studies have shown that even left-handed individuals typically have language functions only in the left hemisphere. However, left-handed individuals are more likely to have a dominance of language in the right hemisphere.


Less common causes of expressive aphasia include primary autoimmune phenomenon and autoimmune phenomenon that are secondary to cancer (as a paraneoplastic syndrome) have been listed as the primary hypothesis for several cases of aphasia, especially when presenting with other psychiatric disturbances and focal neurological deficits. Many case reports exist describing paraneoplastic aphasia, and the reports that are specific tend to describe expressive aphasia. Although most cases attempt to exclude micrometastasis, it is likely that some cases of paraneoplastic aphasia are actually extremely small metastasis to the vocal motor regions.


Neurodegenerative disorders may present with aphasia. Alzheimer's disease may present with either fluent aphasia or expressive aphasia. There are case reports of Creutzfeldt-Jakob disease presenting with expressive aphasia.


Expressive aphasia is classified as non-fluent aphasia, as opposed to fluent aphasia. Diagnosis is done on a case-by-case basis, as lesions often affect the surrounding cortex and deficits are highly variable among patients with aphasia.


A physician is typically the first person to recognize aphasia in a patient who is being treated for damage to the brain. Routine processes for determining the presence and location of lesion in the brain include magnetic resonance imaging (MRI) and computed tomography (CT) scans. The physician will complete a brief assessment of the patient's ability to understand and produce language. For further diagnostic testing, the physician will refer the patient to a speech-language pathologist, who will complete a comprehensive evaluation.


In order to diagnose a patient who is suffering from Broca's aphasia, there are certain commonly used tests and procedures. The Western Aphasia Battery (WAB) classifies individuals based on their scores on the subtests; spontaneous speech, auditory comprehension, repetition, and naming. The Boston Diagnostic Aphasia Examination (BDAE) can inform users what specific type of aphasia they may have, infer the location of lesion, and assess current language abilities. The Porch Index of Communication Ability (PICA) can predict potential recovery outcomes of the patients with aphasia. Quality of life measurement is also an important assessment tool. Tests such as the Assessment for Living with Aphasia (ALA) and the Satisfaction with Life Scale (SWLS) allow for therapists to target skills that are important and meaningful for the individual.


In addition to formal assessments, patient and family interviews are valid and important sources of information. The patient's previous hobbies, interests, personality, and occupation are all factors that will not only impact therapy but may motivate them throughout the recovery process. Patient interviews and observations allow professionals to learn the priorities of the patient and family and determine what the patient hopes to regain in therapy. Observations of the patient may also be beneficial to determine where to begin treatment. The current behaviors and interactions of the patient will provide the therapist with more insight about the client and their individual needs. Other information about the patient can be retrieved from medical records, patient referrals from physicians, and the nursing staff.


In non-speaking patients who use manual languages, diagnosis is often based on interviews from the patient's acquaintances, noting the differences in sign production pre- and post-damage to the brain. Many of these patients will also begin to rely on non-linguistic gestures to communicate, rather than signing since their language production is hindered.


Currently, there is no standard treatment for expressive aphasia. Most aphasia treatment is individualized based on a patient's condition and needs as assessed by a speech language pathologist. Patients go through a period of spontaneous recovery following brain injury in which they regain a great deal of language function.


In the months following injury or stroke, most patients receive traditional treatment for a few hours per day. Among other exercises, patients practice the repetition of words and phrases. Mechanisms are also taught in traditional treatment to compensate for lost language function such as drawing and using phrases that are easier to pronounce.


Emphasis is placed on establishing a basis for communication with family and caregivers in everyday life. Treatment is individualized based on the patient's own priorities, along with the family's input.


A patient may have the option of individual or group treatment. Although less common, group treatment has been shown to have advantageous outcomes. Some types of group treatments include family counseling, maintenance groups, support groups and treatment groups.


Melodic intonation therapy was inspired by the observation that individuals with non-fluent aphasia sometimes can sing words or phrases that they normally cannot speak. "Melodic Intonation Therapy was begun as an attempt to use the intact melodic/prosodic processing skills of the right hemisphere in those with aphasia to help cue retrieval words and expressive language." It is believed that this is because singing capabilities are stored in the right hemisphere of the brain, which is likely to remain unaffected after a stroke in the left hemisphere. However, recent evidence demonstrates that the capability of individuals with aphasia to sing entire pieces of text may actually result from rhythmic features and the familiarity with the lyrics.


The goal of Melodic Intonation Therapy is to utilize singing to access the language-capable regions in the right hemisphere and use these regions to compensate for lost function in the left hemisphere. The natural musical component of speech was used to engage the patients' ability to produce phrases. A clinical study revealed that singing and rhythmic speech may be similarly effective in the treatment of non-fluent aphasia and apraxia of speech. Moreover, evidence from randomized controlled trials is still needed to confirm that Melodic Intonation Therapy is suitable to improve propositional utterances and speech intelligibility in individuals with (chronic) non-fluent aphasia and apraxia of speech.


A pilot study reported positive results when comparing the efficacy of a modified form of MIT to no treatment in people with nonfluent aphasia with damage to their left-brain. A randomized controlled trial was conducted and the study reported benefits of utilizing modified MIT treatment early in the recovery phase for people with nonfluent aphasia.


Melodic Intonation Therapy is used by music therapists, board-certified professionals that use music as a therapeutic tool to effect certain non-musical outcomes in their patients. Speech language pathologists can also use this therapy for individuals who have had a left hemisphere stroke and non-fluent aphasias such as Broca's or even apraxia of speech.


Two important principles of constraint-induced aphasia therapy are that treatment is very intense, with sessions lasting for up to 6 hours over the course of 10 days and that language is used in a communication context in which it is closely linked to (nonverbal) actions. These principles are motivated by neuroscience insights about learning at the level of nerve cells (synaptic plasticity) and the coupling between cortical systems for language and action in the human brain. Constraint-induced therapy contrasts sharply with traditional therapy by the strong belief that mechanisms to compensate for lost language function, such as gesturing or writing, should not be used unless absolutely necessary, even in everyday life.


It is believed that CIAT works by the mechanism of increased neuroplasticity. By constraining an individual to use only speech, it is believed that the brain is more likely to reestablish old neural pathways and recruit new neural pathways to compensate for lost function.


The strongest results of CIAT have been seen in patients with chronic aphasia (lasting over 6 months). Studies of CIAT have confirmed that further improvement is possible even after a patient has reached a "plateau" period of recovery. It has also been proven that the benefits of CIAT are retained long term. However, improvements only seem to be made while a patient is undergoing intense therapy. Recent work has investigated combining constraint-induced aphasia therapy with drug treatment, which led to an amplification of therapy benefits.


In addition to active speech therapy, pharmaceuticals have also been considered as a useful treatment for expressive aphasia. This area of study is relatively new and much research continues to be conducted.


The following drugs have been suggested for use in treating aphasia and their efficacy has been studied in control studies.


The most effect has been shown by piracetam and amphetamine, which may increase cerebral plasticity and result in an increased capability to improve language function. It has been seen that piracetam is most effective when treatment is begun immediately following stroke. When used in chronic cases it has been much less efficient.


Bromocriptine has been shown by some studies to increase verbal fluency and word retrieval with therapy than with just therapy alone. Furthermore, its use seems to be restricted to non-fluent aphasia.


Donepezil has shown a potential for helping chronic aphasia.


No study has established irrefutable evidence that any drug is an effective treatment for aphasia therapy. Furthermore, no study has shown any drug to be specific for language recovery. Comparison between the recovery of language function and other motor function using any drug has shown that improvement is due to a global increase plasticity of neural networks.


In transcranial magnetic stimulation (TMS), magnetic fields are used to create electrical currents in specified cortical regions. The procedure is a painless and noninvasive method of stimulating the cortex. TMS works by suppressing the inhibition process in certain areas of the brain. By suppressing the inhibition of neurons by external factors, the targeted area of the brain may be reactivated and thereby recruited to compensate for lost function. Research has shown that patients can demonstrate increased object naming ability with regular transcranial magnetic stimulation than patients not receiving TMS. Furthermore, research suggests this improvement is sustained upon the completion of TMS therapy. However, some patients fail to show any significant improvement from TMS which indicates the need for further research of this treatment.


It has been proven that, among all types of therapies, one of the most important factors and best predictors for a successful outcome is the intensity of the therapy. By comparing the length and intensity of various methods of therapies, it was proven that intensity is a better predictor of recovery than the method of therapy used.


In most individuals with expressive aphasia, the majority of recovery is seen within the first year following a stroke or injury. The majority of this improvement is seen in the first four weeks in therapy following a stroke and slows thereafter. However, this timeline will vary depending upon the type of stroke experienced by the patient. Patients who experienced an ischemic stroke may recover in the days and weeks following the stroke, and then experience a plateau and gradual slowing of recovery. On the contrary, patients who experienced a hemorrhagic stroke experience a slower recovery in the first 4–8 weeks, followed by a faster recovery which eventually stabilizes.


Numerous factors impact the recovery process and outcomes. Site and extent of lesion greatly impacts recovery. Other factors that may affect prognosis are age, education, gender, and motivation. Occupation, handedness, personality, and emotional state may also be associated with recovery outcomes.


Studies have also found that prognosis of expressive aphasia correlates strongly with the initial severity of impairment. However, it has been seen that continued recovery is possible years after a stroke with effective treatment. Timing and intensity of treatment is another factor that impacts outcomes. Research suggests that even in later stages of recovery, intervention is effective at improving function, as well as, preventing loss of function.


Unlike receptive aphasia, patients with expressive aphasia are aware of their errors in language production. This may further motivate a person with expressive aphasia to progress in treatment, which would affect treatment outcomes. On the other hand, awareness of impairment may lead to higher levels of frustration, depression, anxiety, or social withdrawal, which have been proven to negatively affect a person's chance of recovery.


Expressive aphasia was first identified by the French neurologist Paul Broca. By examining the brains of deceased individuals having acquired expressive aphasia in life, he concluded that language ability is localized in the ventroposterior region of the frontal lobe. One of the most important aspects of Paul Broca's discovery was the observation that the loss of proper speech in expressive aphasia is due to the brain's loss of ability to produce language, as opposed to the mouth's loss of ability to produce words.


The discoveries of Paul Broca were made during the same period of time as the German Neurologist Carl Wernicke, who was also studying brains of aphasiacs post-mortem and identified the region now known as Wernicke's area. Discoveries of both men contributed to the concept of localization, which states that specific brain functions are all localized to a specific area of the brain. While both men made significant contributions to the field of aphasia, it was Carl Wernicke who realized the difference between patients with aphasia that could not produce language and those that could not comprehend language (the essential difference between expressive and receptive aphasia).


Aphasiology is the study of language impairment usually resulting from brain damage, due to neurovascular accident—hemorrhage, stroke—or associated with a variety of neurodegenerative diseases, including different types of dementia. It is also the name of a scientific journal covering the area. These specific language deficits, termed aphasias, may be defined as impairments of language production or comprehension that cannot be attributed to trivial causes such as deafness or oral paralysis. A number of aphasias have been described, but two are best known: expressive aphasia (Broca's aphasia) and receptive aphasia (Wernicke's or sensory aphasia).


Acute aphasias are often the result of tissue damage following a stroke.


Lesions exclusively to Broca's area (the foot of the inferior frontal gyrus) do not produce Broca's aphasia, but instead mild dysprosody and agraphia, sometimes accompanied by word-finding pauses and mild dysarthria. Not much is known about what other areas must be damaged in order to produce Broca's aphasia, but some maintain damage to the inferior pre-Rolandic motor strip (the motor cortex region responsible glossopharyngeal muscle control) is also necessary.


A fascinating corollary of this has come from research on aphasias in deaf users of sign language, who show deficits in signing and comprehension analogous to Expressive and Receptive aphasias in hearing populations. These studies demonstrate that the grammatical functions of Broca's area and the semantic functions of Wernicke's area are indeed deep, abstract properties of the language system independent of its modality of expression.


Another less commonly known aphasia is global aphasia, which generally manifests itself after a stroke affecting an extensive portion of the brain occurs, including infarction of both divisions of the middle cerebral artery and generally both Broca's area and Wernicke's area. Survivors with global aphasia may have great difficulty understanding and forming words and sentences, and generally experience a great deal of difficulty when trying to communicate. With considerable speech therapy rehabilitation, global aphasia may progress into expressive aphasia or receptive aphasia.


A person with anomic aphasia have word-finding difficulties. Anomic aphasia, also known as anomia, is a non-fluent aphasia, which means the person speaks hesitantly because of a difficulty naming words and/or producing correct syntax. The person struggles to find the right words for speaking and writing. Subjects tend to use circumlocutions, in which they speak around the word they can not find, to make up for their loss. People also with anomic aphasia tend to know how to use an object, but rather can not name the aforementioned object. Any damage in or near the zone of language can result in anomic aphasia. Other forms of aphasia often transition into a syndrome of primarily anomic aphasia in the process of recovery.


Conduction Aphasia is a rare form of aphasia in which fibres in the arcuate fasciculus and superior longitudinal fasciculus are damaged. These fibres are the link between the Wernicke's and Broca's area. Damage to the area connecting comprehension and expression together has the following symptoms: fluent speech, good comprehension, poor oral reading, repetition is poor and transpositions of sounds within words is very common.


Primary progressive aphasia is a rare disorder where people slowly lose their ability to talk, read, write, and comprehend what they hear in conversation over a period of time. It was first described as a distinct syndrome by Mesulam in 1982. There are three variants: progressive nonfluent aphasia (PNFA), semantic dementia (SD), and logopenic progressive aphasia (LPA).


MMN refers to the mismatch response in electroencephalography (EEG); MMF or MMNM refer to the mismatch response in magnetoencephalography (MEG).


The auditory MMN was discovered in 1978 by Risto Näätänen, A. W. K. Gaillard, and S. Mäntysalo at the Institute for Perception, TNO in The Netherlands.


The first report of a visual MMN was in 1990 by Rainer Cammer. For a history of the development of the visual MMN, see Pazo-Alvarez et al. (2003).


The auditory MMN can occur in response to deviance in pitch, intensity, or duration. The auditory MMN is a fronto-central negative potential with sources in the primary and non-primary auditory cortex and a typical latency of 150-250 ms after the onset of the deviant stimulus. Sources could also include the inferior frontal gyrus, and the insular cortex. The amplitude and latency of the MMN is related to how different the deviant stimulus is from the standard. Large deviances elicit MMN at earlier latencies. For very large deviances, the MMN can even overlap the N100.


The visual MMN can occur in response to deviance in such aspects as color, size, or duration. The visual MMN is an occipital negative potential with sources in the primary visual cortex and a typical latency of 150-250 ms after the onset of the deviant stimulus.


As kindred phenomena have been elicited with speech stimuli, under passive conditions that require very little active attention to the sound, a version of MMN has been frequently used in studies of neurolinguistic perception, to test whether or not these participants neurologically distinguish between certain kinds of sounds. The MMN response has been used to study how fetuses and newborns discriminate speech sounds. In addition to these kinds of studies focusing on phonological processing, some research has implicated the MMN in syntactic processing. Some of these studies have attempted to directly test the automaticity of the MMN, providing converging evidence for the understanding of the MMN as a task-independent and automatic response.


MMN is evoked by an infrequently presented stimulus ("deviant"), differing from the frequently-occurring stimuli ("standards") in one or several physical parameters like duration, intensity, or frequency. In addition, it is generated by a change in spectrally complex stimuli like phonemes, in synthesised instrumental tones, or in the spectral component of tone timbre. Also the temporal order reversals elicit an MMN when successive sound elements differ either in frequency, intensity, or duration. The MMN is not elicited by stimuli with deviant stimulus parameters when they are presented without the intervening standards. Thus, the MMN has been suggested to reflect change detection when a memory trace representing the constant standard stimulus and the neural code of the stimulus with deviant parameter(s) are discrepant.


The MMN data can be understood as providing evidence that stimulus features are separately analysed and stored in the vicinity of auditory cortex (for a discussion, please see the theory section below). The close resemblance of the behaviour of the MMN to that of the previously behaviourally observed "echoic" memory system strongly suggests that the MMN provides a non-invasive, objective, task-independently measurable physiological correlate of stimulus-feature representations in auditory sensory memory.


The experimental evidence suggests that the auditory sensory memory index MMN provides sensory data for attentional processes, and, in essence, governs certain aspects of attentive information processing. This is evident in the finding that the latency of the MMN determines the timing of behavioural responses to changes in the auditory environment. Furthermore, even individual differences in discrimination ability can be probed with the MMN. The MMN is a component of the chain of brain events causing attention switches to changes in the environment. Attentional instructions also affect MMN.


The MMN has been documented in a number of studies to disclose neuropathological changes.


Presently, the accumulated body of evidence suggests that while the MMN offers unique opportunities to basic research of the information processing of a healthy brain, it might be useful in tapping neurodegenerative changes as well.


MMN, which is elicited irrespective of attention, provides an objective means for evaluating possible auditory discrimination and sensory-memory anomalies in such clinical groups as dyslexics and patients with aphasia, who have a multitude of symptoms including attentional problems. Recent results suggest that a major problem underlying the reading deficit in dyslexia might be an inability of the dyslexics' auditory cortex to adequately model complex sound patterns with fast temporal variation. According to the results of an ongoing study, MMN might also be used in the evaluation of auditory perception deficits in aphasia.


Alzheimer's patients demonstrate decreased amplitude of MMN, especially with long inter-stimulus intervals; this is thought to reflect reduced span of auditory sensory memory. Parkinsonian patients do demonstrate a similar deficit pattern, whereas alcoholism would appear to enhance the MMN response. This latter, seemingly contradictory, finding could be explained by hyperexcitability of CNS neurones resulting from neuroadaptive changes taking place during a heavy drinking bout.


While the results obtained thus far seem encouraging, several steps need to be taken before the MMN can be used as a clinical tool in patient treatment. A focus of research in the late 1990s aimed to tackle some of the key signal-analysis problems encountered in development of clinical use of MMN and challenges still remain. Nevertheless, as it stands, clinical research employing the MMN has already produced significant knowledge on the CNS functional changes related to cognitive decline in the aforementioned clinical disorders.


A 2010 study found that MMN durations were reduced in a group of schizophrenia patients who later went on to have psychotic episodes, suggesting that MMN durations may predict future psychosis.


The mainstream "memory trace" interpretation of MMN is that it is elicited in response to violations of simple rules governing the properties of information. It is thought to arise from violation of an automatically formed, short-term neural model or memory trace of physical or abstract environmental regularities. However, other than MMN, there is no other neurophysiological evidence for the formation of the memory representation of those regularities.


Integral to this memory trace view is that there are:


i) a population of sensory afferent neuronal elements that respond to sound, and;


ii) a separate population of memory neuronal elements that build a neural model of standard stimulation and respond more vigorously when the incoming stimulation violates that neural model, eliciting an MMN.


An alternative "fresh afferent" interpretation is that there are no memory neuronal elements, but the sensory afferent neuronal elements that are tuned to properties of the standard stimulation respond less vigorously upon repeated stimulation. Thus when a deviant activates a distinct new population of neuronal elements that is tuned to the different properties of the deviant rather than the standard, these fresh afferents respond more vigorously, eliciting an MMN.


A third view is that the sensory afferents are the memory neurons.


The bi-directional hypothesis of language and action proposes that the sensorimotor and language comprehension areas of the brain exert reciprocal influence over one another. This hypothesis argues that areas of the brain involved in movement and sensation, as well as movement itself, influence cognitive processes such as language comprehension. In addition, the reverse effect is argued, where it is proposed that language comprehension influences movement and sensation. Proponents of the bi-directional hypothesis of language and action conduct and interpret linguistic, cognitive, and movement studies within the framework of embodied cognition and embodied language processing. Embodied language developed from embodied cognition, and proposes that sensorimotor systems are not only involved in the comprehension of language, but that they are necessary for understanding the semantic meaning of words.


The theory that sensory and motor processes are coupled to cognitive processes stems from action-oriented models of cognition. These theories, such as the embodied and situated cognitive theories, propose that cognitive processes are rooted in areas of the brain involved in movement planning and execution, as well as areas responsible for processing sensory input, termed sensorimotor areas or areas of action and perception. According to action-oriented models, higher cognitive processes evolved from sensorimotor brain regions, thereby necessitating sensorimotor areas for cognition and language comprehension. With this organization, it was then hypothesized that action and cognitive processes exert influence on one another in a bi-directional manner: action and perception influence language comprehension, and language comprehension influences sensorimotor processes.


Effects of Language Comprehension on Systems of Action.


Language comprehension tasks can exert influence over systems of action, both at the neural and behavioral level. This means that language stimuli influence both electrical activity in sensorimotor areas of the brain, as well as actual movement.


The ability of language to influence neural activity of motor systems also manifests itself behaviorally by altering movement. Semantic priming has been implicated in these behavioral changes, and has been used as evidence for the involvement of the motor system in language comprehension. The Action-Sentence Compatibility Effect (ACE) is indicative of these semantic priming effects. Understanding language that implies action may invoke motor facilitation, or prime the motor system, when the action or posture being performed to indicate language comprehension is compatible with action or posture implied by the language. Compatible ACE tasks have been shown to lead to shorter reaction times. This effect has been demonstrated on various types of movements, including hand posture during button pressing, reaching, and manual rotation.


Effects of Systems of Action on Language Comprehension.


The bi-directional hypothesis of action and language proposes that altering the activity of motor systems, either through altered neural activity or actual movement, influences language comprehension. Neural activity in specific areas of the brain can be altered using transcranial magnetic stimulation (TMS), or by studying patients with neuropathologies leading to specific sensory and/or motor deficits. Movement is also used to alter the activity of neural motor systems, increasing overall excitability of motor and pre-motor areas.


Lesions of sensory and motor areas have also been studied to elucidate the effects of sensorimotor systems on language comprehension. One such example of this is the patient JR; this patient has a lesion in areas in the auditory association cortex implicated in processing auditory information. This patient showcases significant impairments in conceptual and perceptual processing of sound-related language and objects. For example, processing the meaning of words describing sound-related objects (e.g., "bell') was significantly impaired in JR as compared to non-sound-related objects (e.g., "armchair"). These data suggest that damage of sensory regions involved in processing auditory information specifically impair processing of sound-related conceptual information, highlighting the necessity of sensory systems for language comprehension.


Movement has been shown to influence language comprehension. This has been demonstrated by priming motor areas with movement, increasing the excitability of motor and pre-motor areas associated with the body part being moved. It has been demonstrated that motor engagement of a specific body part decreases neural activity in language processing areas when processing words related to that body part. This decreased neural activity is a feature of semantic priming, and suggests that activation of specific motor areas through movement can facilitate language comprehension in a semantically-dependent manner. An interference effect has also been demonstrated. During incompatible ACE conditions, neural signatures of language comprehension have been shown to be inhibited. Combined, these pieces of evidence have been used to support a semantic role of the motor system.


Movement can also inhibit language comprehension tasks, particularly tasks of verbal working memory. When asked to memorize and verbally recall four-word sequences of either arm or leg action words, performing complex, rhythmic movements after presentation of the word sequences was demonstrated to interfere with memory performance. This performance deficit was body-part specific, where movement of the legs impaired performance of recall of leg words, and movement of the arms impaired recall of arm words. These data indicate that sensorimotor systems exhibit cortically specific "inhibitory casual effects" on memory of action words, as impairment was specific to motor engagement and bodily association of the words.


Relating cognitive functions to brain structures is done in the field of cognitive neuroscience. This field attempts to map cognitive processes, such as language comprehension, onto neural activation of specific brain structures.The bi-directional hypothesis of language and action requires that action and language processes have overlapping brain structures, or shared neural substrates, thereby necessitating motor areas for language comprehension. The neural substrates of embodied cognition are often studied using the cognitive tasks of object recognition, action recognition, working memory tasks, and language comprehension tasks. These networks have been elucidated with behavioral, computational, and imaging studies, but the discovery of their exact organization is ongoing.


A Jabberwocky sentence is a type of sentence of interest in neurolinguistics. Jabberwocky sentences take their name from the language of Lewis Carroll's well-known poem "Jabberwocky". In the poem, Carroll uses correct English grammar and syntax, but many of the words are made up and merely suggest meaning. A Jabberwocky sentence is therefore a sentence which uses correct grammar and syntax but contains nonsense words, rendering it semantically meaningless.


A second study by Silva-Pereyra et al. showed that preschoolers at the age of 36 months demonstrate similar processing patterns compared to adults when processing normal sentences with phrase structure violations, showing ERP activity analogous to the N150 and P600 in adults, but shifted later in time. When presented with phrase-structure violations in Jabberwocky sentences, however, preschoolers demonstrate activity analogous to a N400, typically associated with the extraction of meaning from words in adults, along with a diminished P600. This implies that semantics plays a role in syntactic processing in children and provides neurobiological evidence for interactive theories over modular theories of semantic and syntactic processing.


The motor theory of speech perception is the hypothesis that people perceive spoken words by identifying the vocal tract gestures with which they are pronounced rather than by identifying the sound patterns that speech generates. It originally claimed that speech perception is done through a specialized module that is innate and human-specific. Though the idea of a module has been qualified in more recent versions of the theory, the idea remains that the role of the speech motor system is not only to produce speech articulations but also to detect them.


The hypothesis has gained more interest outside the field of speech perception than inside. This has increased particularly since the discovery of mirror neurons that link the production and perception of motor movements, including those made by the vocal tract.


The theory was initially proposed in the Haskins Laboratories in the 1950s by Alvin Liberman and Franklin S. Cooper, and developed further by Donald Shankweiler, Michael Studdert-Kennedy, Ignatius Mattingly, Carol Fowler and Douglas Whalen.


The hypothesis has its origins in research using pattern playback to create reading machines for the blind that would substitute sounds for orthographic letters. This led to a close examination of how spoken sounds correspond to the acoustic spectrogram of them as a sequence of auditory sounds. This found that successive consonants and vowels overlap in time with one another (a phenomenon known as coarticulation). This suggested that speech is not heard like an acoustic "alphabet" or "cipher," but as a "code" of overlapping speech gestures.


Initially, the theory was associationist: infants mimic the speech they hear and that this leads to behavioristic associations between articulation and its sensory consequences. Later, this overt mimicry would be short-circuited and become speech perception. This aspect of the theory was dropped, however, with the discovery that prelinguistic infants could already detect most of the phonetic contrasts used to separate different speech sounds.


The behavioristic approach was replaced by a cognitivist one in which there was a speech module. The module detected speech in terms of hidden distal objects rather than at the proximal or immediate level of their input. The evidence for this was the research finding that speech processing was special such as duplex perception.


Initially, speech perception was assumed to link to speech objects that were both


This was later revised to include the phonetic gestures rather than motor commands, and then the gestures intended by the speaker at a prevocal, linguistic level, rather than actual movements.


The "speech is special" claim has been dropped, as it was found that speech perception could occur for nonspeech sounds (for example, slamming doors for duplex perception).


The discovery of mirror neurons has led to renewed interest in the motor theory of speech perception, and the theory still has its advocates, although there are also critics.


If speech is identified in terms of how it is physically made, then nonauditory information should be incorporated into speech percepts even if it is still subjectively heard as "sounds". This is, in fact, the case.


If people can hear the gestures in speech, then the imitation of speech should be very fast, as in when words are repeated that are heard in headphones as in speech shadowing. People can repeat heard syllables more quickly than they would be able to produce them normally.


Evidence exists that perception and production are generally coupled in the motor system. This is supported by the existence of mirror neurons that are activated both by seeing (or hearing) an action and when that action is carried out. Another source of evidence is that for common coding theory between the representations used for perception and action.


The motor theory of speech perception is not widely held in the field of speech perception, though it is more popular in other fields, such as theoretical linguistics. As three of its advocates have noted, "it has few proponents within the field of speech perception, and many authors cite it primarily to offer critical commentary".p. 361 Several critiques of it exist.


Speech perception is affected by nonproduction sources of information, such as context. Individual words are hard to understand in isolation but easy when heard in sentence context. It therefore seems that speech perception uses multiple sources that are integrated together in an optimal way.


The motor theory of speech perception would predict that speech motor abilities in infants predict their speech perception abilities, but in actuality it is the other way around. It would also predict that defects in speech production would impair speech perception, but they do not. However, this only affects the first and already superseded behaviorist version of the theory, where infants were supposed to learn "all" production-perception patterns by imitation early in childhood. This is no longer the mainstream view of motor-speech theorists.


Several sources of evidence for a specialized speech module have failed to be supported.


As a result, this part of the theory has been dropped by some researchers.


The evidence provided for the motor theory of speech perception is limited to tasks such as syllable discrimination that use speech units not full spoken words or spoken sentences. As a result, "speech perception is sometimes interpreted as referring to the perception of speech at the sublexical level. However, the ultimate goal of these studies is presumably to understand the neural processes supporting the ability to process speech sounds under ecologically valid conditions, that is, situations in which successful speech sound processing ultimately leads to contact with the mental lexicon and auditory comprehension." This however creates the problem of " a tenuous connection to their implicit target of investigation, speech recognition".


It has been suggested that birds also hear each other's bird song in terms of vocal gestures.


The coining of the term "neurolinguistics" is attributed to Edith Crowell Trager, Henri Hecaen and Alexandr Luria, in the late 1940s and 1950s; Luria's book "Problems in Neurolinguistics" is likely the first book with Neurolinguistics in the title. Harry Whitaker popularized neurolinguistics in the United States in the 1970s, founding the journal "Brain and Language" in 1974.


Although aphasiology is the historical core of neurolinguistics, in recent years the field has broadened considerably, thanks in part to the emergence of new brain imaging technologies (such as PET and fMRI) and time-sensitive electrophysiological techniques (EEG and MEG), which can highlight patterns of brain activation as people engage in various language tasks; electrophysiological techniques, in particular, emerged as a viable method for the study of language in 1980 with the discovery of the N400, a brain response shown to be sensitive to semantic issues in language comprehension. The N400 was the first language-relevant event-related potential to be identified, and since its discovery EEG and MEG have become increasingly widely used for conducting language research.


Neurolinguistics is closely related to the field of psycholinguistics, which seeks to elucidate the cognitive mechanisms of language by employing the traditional techniques of experimental psychology; today, psycholinguistic and neurolinguistic theories often inform one another, and there is much collaboration between the two fields.


Neurolinguistics research is carried out in all the major areas of linguistics; the main linguistic subfields, and how neurolinguistics addresses them, are given in the table below.


Neurolinguistics research investigates several topics, including where language information is processed, how language processing unfolds over time, how brain structures are related to language acquisition and learning, and how neurophysiology can contribute to speech and language pathology.


Much work in neurolinguistics has, like Broca's and Wernicke's early studies, investigated the locations of specific language "modules" within the brain. Research questions include what course language information follows through the brain as it is processed, whether or not particular areas specialize in processing particular sorts of information, how different brain regions interact with one another in language processing, and how the locations of brain activation differ when a subject is producing or perceiving a language other than his or her first language.


Another area of neurolinguistics literature involves the use of electrophysiological techniques to analyze the rapid processing of language in time. The temporal ordering of specific patterns of brain activity may reflect discrete computational processes that the brain undergoes during language processing; for example, one neurolinguistic theory of sentence parsing proposes that three brain responses (the ELAN, N400, and P600) are products of three different steps in syntactic and semantic processing.


Another topic is the relationship between brain structures and language acquisition. Research in first language acquisition has already established that infants from all linguistic environments go through similar and predictable stages (such as babbling), and some neurolinguistics research attempts to find correlations between stages of language development and stages of brain development, while other research investigates the physical changes (known as neuroplasticity) that the brain undergoes during second language acquisition, when adults learn a new language.


Neuroplasticity is observed when both Second Language acquisition and Language Learning experience are induced, the result of this language exposure concludes that an increase of gray and white matter could be found in children, young adults and the elderly.


Ping Li, Jennifer Legault, Kaitlyn A. Litcofsky, May 2014.


Neuroplasticity as a function of second language learning: Anatomical changes in the human brain


Cortex: A Journal Devoted to the Study of the Nervous System & Behavior, 410.1016/j.cortex.2014.05.00124996640


Neurolinguistic techniques are also used to study disorders and breakdowns in language, such as aphasia and dyslexia, and how they relate to physical characteristics of the brain.


Since one of the focuses of this field is the testing of linguistic and psycholinguistic models, the technology used for experiments is highly relevant to the study of neurolinguistics. Modern brain imaging techniques have contributed greatly to a growing understanding of the anatomical organization of linguistic functions. Brain imaging methods used in neurolinguistics may be classified into hemodynamic methods, electrophysiological methods, and methods that stimulate the cortex directly.


In addition to PET and fMRI, which show which areas of the brain are activated by certain tasks, researchers also use diffusion tensor imaging (DTI), which shows the neural pathways that connect different brain areas, thus providing insight into how different areas interact. Functional near-infrared spectroscopy (fNIRS) is another hemodynamic method used in language tasks.


Neurolinguists employ a variety of experimental techniques in order to use brain imaging to draw conclusions about how language is represented and processed in the brain. These techniques include the "subtraction" paradigm, "mismatch design", "violation-based" studies, various forms of "priming", and "direct stimulation" of the brain.


Many language studies, particularly in fMRI, use the subtraction paradigm, in which brain activation in a task thought to involve some aspect of language processing is compared against activation in a baseline task thought to involve similar non-linguistic processes but not to involve the linguistic process. For example, activations while participants read words may be compared to baseline activations while participants read strings of random letters (in attempt to isolate activation related to lexical processing—the processing of real words), or activations while participants read syntactically complex sentences may be compared to baseline activations while participants read simpler sentences.


In psycholinguistics and neurolinguistics, "priming" refers to the phenomenon whereby a subject can recognize a word more quickly if he or she has recently been presented with a word that is similar in meaning or morphological makeup (i.e., composed of similar parts). If a subject is presented with a "prime" word such as "doctor" and then a "target" word such as "nurse", if the subject has a faster-than-usual response time to "nurse" then the experimenter may assume that word "nurse" in the brain had already been accessed when the word "doctor" was accessed. Priming is used to investigate a wide variety of questions about how words are stored and retrieved in the brain and how structurally complex sentences are processed.


In many neurolinguistics experiments, subjects do not simply sit and listen to or watch stimuli, but also are instructed to perform some sort of task in response to the stimuli. Subjects perform these tasks while recordings (electrophysiological or hemodynamic) are being taken, usually in order to ensure that they are paying attention to the stimuli. At least one study has suggested that the task the subject does has an effect on the brain responses and the results of the experiment.


The lexical decision task involves subjects seeing or hearing an isolated word and answering whether or not it is a real word. It is frequently used in priming studies, since subjects are known to make a lexical decision more quickly if a word has been primed by a related word (as in "doctor" priming "nurse").


Many studies, especially violation-based studies, have subjects make a decision about the "acceptability" (usually grammatical acceptability or semantic acceptability) of stimuli. Such a task is often used to "ensure that subjects [are] reading the sentences attentively and that they [distinguish] acceptable from unacceptable sentences in the way the [experimenter] expect[s] them to do."


Experimental evidence has shown that the instructions given to subjects in an acceptability judgment task can influence the subjects' brain responses to stimuli. One experiment showed that when subjects were instructed to judge the "acceptability" of sentences they did not show an N400 brain response (a response commonly associated with semantic processing), but that they did show that response when instructed to ignore grammatical acceptability and only judge whether or not the sentences "made sense".


Some studies use a "probe verification" task rather than an overt acceptability judgment; in this paradigm, each experimental sentence is followed by a "probe word", and subjects must answer whether or not the probe word had appeared in the sentence. This task, like the acceptability judgment task, ensures that subjects are reading or listening attentively, but may avoid some of the additional processing demands of acceptability judgments, and may be used no matter what type of violation is being presented in the study.


Subjects may be instructed not to judge whether or not the sentence is grammatically acceptable or logical, but whether the proposition expressed by the sentence is true or false. This task is commonly used in psycholinguistic studies of child language.


Another related form of experiment is the double-task experiment, in which a subject must perform an extra task (such as sequential finger-tapping or articulating nonsense syllables) while responding to linguistic stimuli; this kind of experiment has been used to investigate the use of working memory in language processing.


Some relevant journals include the "Journal of Neurolinguistics" and "Brain and Language". Both are subscription access journals, though some abstracts may be generally available.


Clinical linguistics is a sub-discipline of applied linguistics involved in the description, analysis, and treatment of language disabilities, especially the application of linguistic theory to the field of Speech-Language Pathology. The study of the linguistic aspect of communication disorders is of relevance to a broader understanding of language and linguistic theory.


The International Clinical Phonetics and Linguistics Association is the unofficial organization of the field and was formed in 1991. The Journal of Clinical Linguistics and Phonetics is the major research journal of the field and was founded by Martin J. Ball.


Practitioners of clinical linguistics typically work in Speech-Language Pathology departments or linguistics departments. They conduct research with the aims of improving the assessment, treatment, and analysis of disordered speech and language, and offering insights to formal linguistic theories. While the majority of clinical linguistics journals still focus only on English linguistics, there is an emerging movement toward comparative clinical linguistics across multiple languages.


The study of communication disorders has a history that can be traced all the way back to the ancient Greeks. Modern clinical linguistics, however, largely has its roots in the twentieth century, with the term ‘clinical linguistics’ gaining wider currency in the 1970s, with it being used as the title of a book by prominent linguist David Crystal in 1981. Widely credited as the ‘father of clinical linguistics’, Crystal's book "Clinical Linguistics" went on to become one of the most influential books of the field, as this new discipline was mapped out in great detail.


These are the main disciplines of clinical linguistics:


Phonetics is a branch of linguistics that studies the sounds of human speech. Clinical phonetics involve applications of phonetics to describe speech differences and disorders, including information about speech sounds and the perceptual skills used in clinical settings.


Phonology is one of the branches of linguistics that is concerned with the systematic organization of sounds in spoken languages and signs in sign languages. Unlike clinical phonetics, clinical phonology focuses on the application of phonology on interpretations of speech sounds in a particular language and how it deals with phoneme.


In linguistics, prosody is concerned with elements of speech that are not individual phonetic segments (vowels and consonants) but are properties of syllables and larger units of speech. Prosody is essential in communicative functions such as expressing emotions or affective states.


Morphology is the study of words, how they are formed, and their relationship to other words in the same language. It analyses the structure of words and part of words, such as stems, root words, prefixes, and suffixes.


Syntax is the set of rules, principles and processes that govern the structure of sentences in a given language, usually including word order. Every language has a different set of syntactic rules, but all languages have some form of syntax.


Semantics is the study of the interpretation of signs or symbols used in agents or communities within particular circumstances and contexts .


Pragmatics is a subfield of linguistics and semiotics that studies the ways in which context contributes to meaning. It refers to the description and classification of pragmatic impairments, their elucidation in terms of various pragmatic, linguistics, cognitive and neurological theories, and their assessment and treatment.


In corpus linguistics, discourse refers to the study of language expressed in corpora (samples) of “real world” text, the codified language of a field of enquiry, or a statement that determines the connections among language and structure and agency.


Linguistic concepts and theories are applied to assess, diagnose and administer language disorders. These theories and concepts commonly involve psycholinguistics and sociolinguistics. Clinical linguists adopt the understanding of language and the linguistic disciplines, as mentioned above, to explain language disorders and find approaches to treat them. Crystal pointed out that applications of linguistics to clinical ends are highly relational. In his book ‘Clinical Linguistics’, Crystal references many commonly known disorders with linguistic knowledge. Some examples from his book are as follows:


Some broad linguistics methods that are commonly used in the treatment of patients mentioned by Cummings (2017) include:


The past works of linguists such as Crystal were applicable to a wide range of communication disorders at every linguistic level. However, with the influx of new insights from disciplines such as genetics, cognitive neuroscience and neurobiology (among others), it is no longer sufficient to just focus on the linguistic characteristics of a particular speech impairment.


In today's context, one of the challenges in clinical linguistics includes identifying methods to bridge the knowledge of different fields to build a more holistic understanding. The translation of general research that has been done into effective tools for clinical practice is another aspect that requires future work.


The N400 is a component of time-locked EEG signals known as event-related potentials (ERP). It is a negative-going deflection that peaks around 400 milliseconds post-stimulus onset, although it can extend from 250-500 ms, and is typically maximal over centro-parietal electrode sites. The N400 is part of the normal brain response to words and other meaningful (or potentially meaningful) stimuli, including visual and auditory words, sign language signs, pictures, faces, environmental sounds, and smells.


An example of an experimental task used to study the N400 is a priming paradigm. Subjects are shown a list of words in which a prime word is either associatively related to a target word (e.g. bee and honey), semantically related (e.g. sugar and honey) or a direct repetition (e.g. honey and honey). The N400 amplitude seen to the target word (honey) will be reduced upon repetition due to semantic priming. The amount of reduction in amplitude can be used to measure the degree of relatedness between the words.


Another widely used experimental task used to study the N400 is sentence reading. In this kind of study, sentences are presented to subjects centrally, one word at a time, until the sentence is completed. Alternatively, subjects could listen to a sentence as natural auditory speech. Again, subjects may be asked to respond to comprehension questions periodically throughout the experiment, although this is not necessary. Experimenters can choose to manipulate various linguistic characteristics of the sentences, including contextual constraint or the cloze probability of the sentence-final word (see below for a definition of cloze probability) to observe how these changes affect the waveform's amplitude.


As previously mentioned, the N400 response is seen to all meaningful, or potentially meaningful, stimuli. As such, a wide range of paradigms can be used to study it. Experiments involving the presentation of spoken words, acronyms, pictures embedded at the end of sentences, music, words related to current context or orientation and videos of real-word events, have all been used to study the N400, just to name a few.


Extensive research has been carried out to better understand what kinds of experimental manipulations do and do not affect the N400. General findings are discussed below.


The frequency of a word's usage is known to affect the amplitude of the N400. With all else being constant, highly frequent words elicit reduced N400s relative to infrequent words. As previously mentioned, N400 amplitude is also reduced by repetition, such that a word's second presentation exhibits a more positive response when repeated in context. These findings suggest that when a word is highly frequent or has recently appeared in context, it eases the semantic processing thought to be indexed by the N400, reducing its amplitude.


N400 amplitude is also sensitive to a word's orthographic neighborhood size, or how many other words differ from it by only one letter (e.g. "boot" and "boat"). Words with large neighborhoods (that have many other physically similar items) elicit larger N400 amplitudes than do words with small neighborhoods. This finding also holds true for pseudowords, or pronounceable letter strings that are not real words (e.g. flom), which are not themselves meaningful but look like words. This has been taken as evidence that the N400 reflects general activation in the comprehension network, such that items that look like many words (regardless of whether it itself is a word) partially activate the representations of similar-looking words, producing a more negative N400.


The N400 is sensitive to priming: in other words, its amplitude is reduced when a target word is preceded by a word that is semantically, morphologically, or orthographically related to it.


Factors that do not affect N400 amplitude.


Additionally, grammatical violations do not elicit a large N400 response. Rather, these types of violations show a large positivity from about 500-1000 ms after stimulus onset, known as the P600.


A striking feature of the N400 is the general invariance of its peak latency. Although many different experimental manipulations affect the amplitude of the N400, few factors (aging and disease states and language proficiency being rare examples) alter the time it takes for the N400 component to reach a peak amplitude.


Although localization of the neural generators of an ERP signal is difficult due to the spreading of current from the source to the sensors, multiple techniques can be used to provide converging evidence about possible neural sources. Using methods such as recordings directly off the surface of the brain or from electrodes implanted in the brain, evidence from brain damaged patients, and magnetoencephalographic (MEG) recordings (which measure magnetic activity at the scalp associated with the electrical signal measured by ERPs), the left temporal lobe has been highlighted as an important source for the N400, with additional contributions from the right temporal lobe. More generally, however, activity in a wide network of brain areas is elicited in the N400 time window, suggesting a highly distributed neural source.


There is still much debate as to exactly what kind of neural and comprehension processes the N400 indexes. Some researchers believe that the underlying processes reflected in the N400 occur after a stimulus has been recognized. For example, Brown and Hagoort (1993) believe that the N400 occurs late in the processing stream, and reflects the integration of a word's meaning into the preceding context (see Kutas & Federmeier, in press, for a discussion). However, this account has not explained why items that themselves have no meaning (e.g. pseudowords without defined associations) also elicit the N400. Other researchers believe that the N400 occurs much earlier, before words are recognized, and represents orthographic or phonological analysis.


More recent accounts posit that the N400 represents a broader range of processes indexing access to semantic memory. According to this account, it represents the binding of information obtained from stimulus input with representations from short- and long-term memory (such as recent context, and accessing a word's meaning in long term memory) that work together to create meaning from the information available in the current context (Federmeier & Laszlo, 2009; see Kutas & Federmeier, in press).


Another account is that the N400 reflects prediction error or surprisal. Word-based surprisal was a strong predictor of N400 amplitude in an ERP corpus. In addition, connectionist models make use of prediction error for learning and linguistic adaptation, and these models can explain several N400/P600 results in terms of prediction error propagation for learning.


As research in the field of electrophysiology continues to progress, these theories will likely be refined to include a complete account of just what the N400 represents.


The notion of a dedicated language module in the human brain originated with Noam Chomsky's theory of Universal Grammar (UG). The debate on the issue of modularity in language is underpinned, in part, by different understandings of this concept. There is, however, some consensus in the literature that a module is considered committed to processing specialized representations (domain-specificity) (Bryson and Stein, 2001) in an informationally encapsulated way. A distinction should be drawn between anatomical modularity, which proposes there is one 'area' in the brain that deals with this processing, and functional modularity that obviates anatomical modularity whilst maintaining information encapsulation in distributed parts of the brain.


The available evidence points towards no one anatomical area solely devoted to processing language. The Wada test, where sodium amobarbital is used to anaesthetise one hemisphere, shows that the left-hemisphere appears to be crucial in language processing. Yet, neuroimaging does not implicate any single area but rather identifies many different areas as being involved in different aspects of language processing. and not just in the left hemisphere. Further, individual areas appear to subserve a number of different functions. Thus, the extent to which language processing occurs within an anatomical module is considered to be minimal. Nevertheless, as many have suggested, modular processing can still exist even when implemented across the brain; that is, language processing could occur within a functional module.


No double dissociation – acquired or developmental.


A common way to demonstrate modularity is to find a double dissociation. That is two groups: First, people for whom language is severely damaged and yet have normal cognitive abilities and, second, persons for whom normal cognitive abilities are grossly impaired and yet language remains intact. Whilst extensive lesions in the left hemisphere perisylvian area can render persons unable to produce or perceive language (global aphasia), there is no known acquired case where language is completely intact in the face of severe non-linguistic deterioration. Thus, functional module status cannot be granted to language processing based on this evidence.


Thus, the evidence from double dissociations does not support modularity, although lack of dissociation is not evidence against a module; this inference cannot be logically made.


Indeed, if language were a module it would be informationally encapsulated. Yet, there is evidence to suggest that this is not the case. For instance, in the McGurk effect, watching lips say one phoneme whilst another is played creates the percept of a blended phoneme. Further, Tanenhaus, Spivey-Knowlton, Eberhard and Sedivy (1995) demonstrated visual information mediating syntactic processing. In addition, the putative language module should process only that information relevant to language (i.e., be domain-specific). Yet evidence suggests that areas purported to subserve language also mediate motor control and non-linguistic sound comprehension. Although it is possible that separate processes could be occurring but below the resolution of current imaging techniques, when all this evidence is taken together the case for information encapsulation is weakened.


The alternative, as it is framed, is that language occurs within a more general cognitive system. The counterargument is that there appears to be something ‘special’ about human language. This is usually supported by evidence such as all attempts to teach animals human languages to any great success have failed (Hauser et al. 2003) and that language can be selectively damaged (a single dissociation) suggesting proprietary computation may be required. Instead of postulating 'pure' modularity, theorists have opted for a weaker version, domain-specificity implemented in functionally specialised neural circuits and computation (e.g. Jackendoff and Pinker’s words, we must investigate language “not as a monolith but as a combination of components, some special to language, others rooted in more general capacities”).


Multilingualism is the use of more than one language, either by an individual speaker or by a group of speakers. It is believed that multilingual speakers outnumber monolingual speakers in the world's population. More than half of all Europeans claim to speak at least one language other than their mother tongue; but many read and write in one language. Always useful to traders, multilingualism is advantageous for people wanting to participate in globalization and cultural openness. Owing to the ease of access to information facilitated by the Internet, individuals' exposure to multiple languages is becoming increasingly possible. People who speak several languages are also called polyglots.


Multilingual speakers have acquired and maintained at least one language during childhood, the so-called first language (L1). The first language (sometimes also referred to as the mother tongue) is usually acquired without formal education, by mechanisms about which scholars disagree. Children acquiring two languages natively from these early years are called simultaneous bilinguals. It is common for young simultaneous bilinguals to be more proficient in one language than the other.


People who speak more than one language have been reported to be more adept at language learning compared to monolinguals.


Multilingualism in computing can be considered part of a continuum between internationalization and localization. Due to the status of English in computing, software development nearly always uses it (but not in the case of non-English-based programming languages). Some commercial software is initially available in an English version, and multilingual versions, if any, may be produced as alternative options based on the English original.


The definition of multilingualism is a subject of debate in the same way as that of language fluency. At one end of a sort of linguistic continuum, one may define multilingualism as complete competence in and mastery of more than one language. The speaker would presumably have complete knowledge and control over the languages and thus sound like a native speaker. At the opposite end of the spectrum would be people who know enough phrases to get around as a tourist using the alternate language. Since 1992, Vivian Cook has argued that most multilingual speakers fall somewhere between minimal and maximal definitions. Cook calls these people "multi-competent".


In addition, there is no consistent definition of what constitutes a distinct language. For instance, scholars often disagree whether Scots is a language in its own right or merely a dialect of English. Furthermore, what is considered a language can change, often for purely political reasons. One example is the creation of Serbo-Croatian as a standard language on the basis of the Eastern Herzegovinian dialect to function as umbrella for numerous South Slavic dialects; after the breakup of Yugoslavia it was split into Serbian, Croatian, Bosnian and Montenegrin. Another example is that Ukrainian was dismissed as a Russian dialect by the Russian tsars to discourage national feelings.


Many small independent nations' schoolchildren are today compelled to learn multiple languages because of international interactions. For example, in Finland, all children are required to learn at least three languages: the two national languages (Finnish and Swedish) and one foreign language (usually English). Many Finnish schoolchildren also study further languages, such as German or Russian.


In some large nations with multiple languages, such as India, schoolchildren may routinely learn multiple languages based on where they reside in the country.


In many countries, bilingualism occurs through international relations, which, with English being the global lingua franca, sometimes results in majority bilingualism even when the countries have just one domestic official language. This is occurring especially in Germanic regions such as Scandinavia, the Benelux and among Germanophones, but it is also expanding into some non-Germanic countries.


Many myths and much prejudice have grown around the notions of bi- and multilingualism in some Western countries where monolingualism is the norm. Researchers from the UK and Poland have listed the most common misconceptions:


These are all harmful convictions that have long been debunked, yet persist among many parents. In reality, bilingual children have lower scores than their monolingual peers when they are assessed in only one of the languages they are acquiring, but have substantially greater total lingual resources.


One view is that of the linguist Noam Chomsky in what he calls the human language acquisition device—a mechanism which enables a learner to recreate correctly the rules and certain other characteristics of language used by surrounding speakers. This device, according to Chomsky, wears out over time, and is not normally available by puberty, which he uses to explain the poor results some adolescents and adults have when learning aspects of a second language (L2).


If language learning is a cognitive process, rather than a language acquisition device, as the school led by Stephen Krashen suggests, there would only be relative, not categorical, differences between the two types of language learning.


Rod Ellis quotes research finding that the earlier children learn a second language, the better off they are, in terms of pronunciation. European schools generally offer secondary language classes for their students early on, due to the interconnectedness with neighbor countries with different languages. Most European students now study at least two foreign languages, a process strongly encouraged by the European Union.


Based on the research in Ann Fathman's "The Relationship between age and second language productive ability," there is a difference in the rate of learning of English morphology, syntax and phonology based upon differences in age, but that the order of acquisition in second language learning does not change with age.


People who learn multiple languages may also experience positive transfer – the process by which it becomes easier to learn additional languages if the grammar or vocabulary of the new language is similar to those of languages already spoken. On the other hand, students may also experience negative transfer – interference from languages learned at an earlier stage of development while learning a new language later in life.


In sequential bilingualism, learners receive literacy instruction in their native language until they acquire a "threshold" literacy proficiency. Some researchers use age 3 as the age when a child has basic communicative competence in their first language (Kessler, 1984). Children may go through a process of sequential acquisition if they migrate at a young age to a country where a different language is spoken, or if the child exclusively speaks his or her heritage language at home until he/she is immersed in a school setting where instruction is offered in a different language.


In simultaneous bilingualism, the native language and the community language are simultaneously taught. The advantage is literacy in two languages as the outcome. However, the teacher must be well-versed in both languages and also in techniques for teaching a second language.


The phases children go through during sequential acquisition are less linear than for simultaneous acquisition and can vary greatly among children. Sequential acquisition is a more complex and lengthier process, although there is no indication that non-language-delayed children end up less proficient than simultaneous bilinguals, so long as they receive adequate input in both languages.


A coordinate model posits that equal time should be spent in separate instruction of the native language and the community language. The native language class, however, focuses on basic literacy while the community language class focuses on listening and speaking skills. Being bilingual does not necessarily mean that one can speak, for example, English and French.


Research has found that the development of competence in the native language serves as a foundation of proficiency that can be transposed to the second language — the common underlying proficiency hypothesis. Cummins' work sought to overcome the perception propagated in the 1960s that learning two languages made for two competing aims. The belief was that the two languages were mutually exclusive and that learning a second required unlearning elements and dynamics of the first to accommodate the second. The evidence for this perspective relied on the fact that some errors in acquiring the second language were related to the rules of the first language. How this hypothesis holds under different types of languages such as Romance versus non-Western languages has yet to undergo research.


Another new development that has influenced the linguistic argument for bilingual literacy is the length of time necessary to acquire the second language. While previously children were believed to have the ability to learn a language within a year, today researchers believe that within and across academic settings, the period is nearer to five years.


An interesting outcome of studies during the early 1990s, however, confirmed that students who do complete bilingual instruction perform better academically. These students exhibit more cognitive elasticity including a better ability to analyze abstract visual patterns. Students who receive bidirectional bilingual instruction where equal proficiency in both languages is required perform at an even higher level. Examples of such programs include international and multi-national education schools.


A multilingual person is someone who can communicate in more than one language actively (through speaking, writing, or signing). Multilingual people can speak any language they write in, but cannot necessarily write in any language they speak. More specifically, bilingual and trilingual people are those in comparable situations involving two or three languages, respectively. A multilingual person is generally referred to as a polyglot, a term that may also refer to people who learn multiple languages as a hobby.


Multilingual speakers have acquired and maintained at least one language during childhood, the so-called first language (L1). The first language (sometimes also referred to as the mother tongue) is acquired without formal education, by mechanisms heavily disputed. Children acquiring two languages in this way are called simultaneous bilinguals. Even in the case of simultaneous bilinguals, one language usually dominates over the other.


The reverse phenomenon, where people who know more than one language end up losing command of some or all of their additional languages, is called language attrition. It has been documented that, under certain conditions, individuals may lose their L1 language proficiency completely, after switching to the exclusive use of another language, and effectively "become native" in a language that was once secondary after the L1 undergoes total attrition.


This is most commonly seen among immigrant communities and has been the subject of substantial academic study. The most important factor in spontaneous, total L1 loss appears to be age; in the absence of neurological dysfunction or injury, only young children typically are at risk of forgetting their native language and switching to a new one. Once they pass an age that seems to correlate closely with the critical period, around the age of 12, total loss of a native language is not typical, although it is still possible for speakers to experience diminished expressive capacity if the language is never practiced.


There are differences between those who learn a language in a class environment and those who learn through total immersion, usually living in a country where the target language is widely spoken. Without the possibility to actively translate in a classroom setting, due to a lack of first language communication opportunity, the comparison between languages is reduced. In an immersive environment, the new language is almost independently learned, like the mother tongue for a child, with a direct concept-to-language translation that can become more natural than word structures learned as a subject. Added to this, the uninterrupted, immediate and exclusive practice of the new language reinforces and deepens the attained knowledge.


Bilinguals might have important labor market advantages over monolingual individuals as bilingual people can carry out duties that monolinguals cannot, such as interacting with customers who only speak a minority language. A study in Switzerland has found that multilingualism is positively correlated with an individual's salary, the productivity of firms, and the gross domestic production (GDP); the authors state that Switzerland's GDP is augmented by 10% by multilingualism. A study in the United States by Agirdag found that bilingualism has substantial economic benefits as bilingual persons were found to have around $3,000 per year more salary than monolinguals.


While many polyglots know up to six languages, the number drops off sharply past this point. People who speak many more than this—Michael Erard suggests eleven or more—are sometimes classed as "hyperpolyglots". Giuseppe Caspar Mezzofanti, for example, was an Italian priest reputed to have spoken anywhere from 30 to 72 languages. The causes of advanced language aptitude are still under research; one theory suggests that a spike in a baby's testosterone levels while in the uterus can increase brain asymmetry, which may relate to music and language ability, among other effects.


It is important to note that terms past trilingual are rarely used. People who speak four or more languages are generally just referred to as multilingual.


Widespread multilingualism is one form of language contact. Multilingualism was common in the past: in early times, when most people were members of small language communities, it was necessary to know two or more languages for trade or any other dealings outside one's town or village, and this holds good today in places of high linguistic diversity such as Sub-Saharan Africa and India. Linguist Ekkehard Wolff estimates that 50% of the population of Africa is multilingual.


In multilingual societies, not all speakers need to be multilingual. Some states can have multilingual policies and recognize several official languages, such as Canada (English and French). In some states, particular languages may be associated with particular regions in the state (e.g., Canada) or with particular ethnicities (e.g., Malaysia and Singapore). When all speakers are multilingual, linguists classify the community according to the functional distribution of the languages involved:


N.B. the terms given above all refer to situations describing only two languages. In cases of an unspecified number of languages, the terms polyglossia, omnilingualism, and multipart-lingualism are more appropriate.


Whenever two people meet, negotiations take place. If they want to express solidarity and sympathy, they tend to seek common features in their behavior. If speakers wish to express distance towards or even dislike of the person they are speaking to, the reverse is true, and differences are sought. This mechanism also extends to language, as described in the Communication Accommodation Theory.


Some multilinguals use code-switching, which involves swapping between languages. In many cases, code-switching is motivated by the wish to express loyalty to more than one cultural group, as holds for many immigrant communities in the New World. Code-switching may also function as a strategy where proficiency is lacking. Such strategies are common if the vocabulary of one of the languages is not very elaborated for certain fields, or if the speakers have not developed proficiency in certain lexical domains, as in the case of immigrant languages.


This code-switching appears in many forms. If a speaker has a positive attitude towards both languages and towards code-switching, many switches can be found, even within the same sentence. If however, the speaker is reluctant to use code-switching, as in the case of a lack of proficiency, he might knowingly or unknowingly try to camouflage his attempt by converting elements of one language into elements of the other language through calquing. This results in speakers using words like "courrier noir" (literally mail that is black) in French, instead of the proper word for blackmail, "chantage".


With emerging markets and expanding international cooperation, business users expect to be able to use software and applications in their own language. Multilingualisation (or "m17n", where "17" stands for 17 omitted letters) of computer systems can be considered part of a continuum between internationalization and localization:


Translating the user interface is usually part of the software localization process, which also includes adaptations such as units and date conversion. Many software applications are available in several languages, ranging from a handful (the most spoken languages) to dozens for the most popular applications (such as office suites, web browsers, etc.). Due to the status of English in computing, software development nearly always uses it (but see also Non-English-based programming languages), so almost all commercial software is initially available in an English version, and multilingual versions, if any, may be produced as alternative options based on the English original.


According to Hewitt (2008) entrepreneurs in London from Poland, China or Turkey use English mainly for communication with customers, suppliers, and banks, but their native languages for work tasks and social purposes.


Even in English-speaking countries immigrants are still able to use their mother tongue in the workplace thanks to other immigrants from the same place. Kovacs (2004) describes this phenomenon in Australia with Finnish immigrants in the construction industry who spoke Finnish during working hours.


But even though foreign languages may be used in the workplace, English is still a must-know working skill. Mainstream society justifies the divided job market, arguing that getting a low-paying job is the best newcomers can achieve considering their limited language skills.


With companies going international they are now focusing more and more on the English level of their employees. Especially in South Korea since the 1990s, companies are using different English language testing to evaluate job applicants, and the criteria in those tests are constantly upgrading the level for good English. In India, it is even possible to receive training to acquire an English accent, as the number of outsourced call centers in India has soared in the past decades.


Meanwhile, Japan ranks 53rd out of 100 countries in 2019 EF English Proficiency Index, amid calls for this to improve in time for the 2020 Tokyo Olympics.


Within multiracial countries such as Malaysia and Singapore, it is not unusual for one to speak two or more languages, albeit with varying degrees of fluency. Some are proficient in several Chinese dialects, given the linguistic diversity of the ethnic Chinese community in both countries.


Not only in multinational companies is English an important skill, but also in the engineering industry, in the chemical, electrical and aeronautical fields. A study directed by Hill and van Zyl (2002) shows that in South Africa young black engineers used English most often for communication and documentation. However, Afrikaans and other local languages were also used to explain particular concepts to workers in order to ensure understanding and cooperation.


In Europe, as the domestic market is generally quite restricted, international trade is a norm. Languages, that are used in multiple countries, include:


English is a commonly taught second language at schools, so it is also the most common choice for two speakers, whose native languages are different. However, some languages are so close to each other that it is generally more common when meeting to use their mother tongue rather than English. These language groups include:


In multilingual countries such as Belgium (Dutch, French, and German), Switzerland (German, French, Italian and Romansh), Luxembourg (Luxembourgish, French and German) or Spain (Spanish, Catalan, Basque and Galician), it is common to see employees mastering two or even three of those languages.


Many minor Russian ethnic groups, such as Tatars, Bashkirs and others, are also multilingual. Moreover, with the beginning of compulsory study of the Tatar language in Tatarstan, there has been an increase in its level of knowledge of the Russian-speaking population of the republic.


Continued global diversity has led to an increasingly multilingual workforce. Europe has become an excellent model to observe this newly diversified labor culture. The expansion of the European Union with its open labor market has provided opportunities both for well-trained professionals and unskilled workers to move to new countries to seek employment. Political changes and turmoil have also led to migration and the creation of new and more complex multilingual workplaces. In most wealthy and secure countries, immigrants are found mostly in low paid jobs but also, increasingly, in high-status positions.


It is extremely common for music to be written in whatever the contemporary lingua franca is. If a song is not written in a common tongue, then it is usually written in whatever is the predominant language in the musician's country of origin, or in another widely recognized language, such as English, German, Spanish, or French.


The bilingual song cycles "there..." and "Sing, Poetry" on the 2011 contemporary classical album "Troika" consist of musical settings of Russian poems with their English self-translation by Joseph Brodsky and Vladimir Nabokov, respectively.


Songs with lyrics in multiple languages are known as macaronic verse.


American novelists who use foreign languages (outside of their own cultural heritage) for literary effect, include Cormac McCarthy who uses untranslated Spanish and Spanglish in his fiction.


Multilingual poetry is prevalent in US Latino literature where code-switching and translanguaging between English, Spanish, and Spanglish is common within a single poem or throughout a book of poems. Latino poetry is also written in Portuguese and can include phrases in Nahuatl, Mayan, Huichol, Arawakan, and other indigenous languages related to the Latino experience. Contemporary multilingual poets include Giannina Braschi, Ana Castillo, Sandra Cisneros, and Guillermo Gómez-Peña


The P600 is an event-related potential (ERP), or peak in electrical brain activity measured by electroencephalography (EEG). It is a language-relevant ERP and is thought to be elicited by hearing or reading grammatical errors and other syntactic anomalies. Therefore, it is a common topic of study in neurolinguistic experiments investigating sentence processing in the human brain.


The P600 was first reported by Lee Osterhout and Phillip Holcomb in 1992. It is also sometimes called the syntactic positive shift (SPS), since it has a positive polarity and is usually elicited by syntactic phenomena.


The P600 was originally considered a "syntactic" ERP, as it is elicited by several types of syntactic phenomena, including ungrammatical stimuli, garden-path sentences that require reanalysis, complex sentences with a large number of thematic roles, and the processing of filler-gap dependencies (such as wh-words that appear at the beginning of a sentence in English but are actually interpreted somewhere else).


A P600 may be elicited by several kinds of grammatical errors in sentences, such as problems in agreement, such as "the child *"throw" the toy". In addition to this sort of subject-verb disagreement, P600s have also been elicited by disagreements in tense, gender, number, and case, as well as phrase structure violations. A 2009 study has suggested that these errors elicit stronger P600s than the other syntactic stimuli that have been implicated.


P600s are also elicited by errors in musical harmony, such as when a chord is played out of key with the rest of a musical phrase. This implies that P600s are not "language-specific," but "can be elicited in nonlinguistic (but rule-governed) sequences."


demonstrated a so-called "semantic P600" in sentences that are grammatically correct but semantically anomalous, and in which syntactic reanalysis is more appealing than semantic reanalysis. For example, a P600 may be elicited in the following sentence: The hearty meal was devouring the kids.This suggests that the reader would rather interpret the sentence as containing a morphosyntactic error (saying "devour"ing"" instead of "devour"ed by"") rather than a semantic one (meals can't devour kids, but can be devoured by them). The interpretation of "semantic P600s" has attracted considerable attention and controversy in the literature.


Articulatory phonology is a linguistic theory originally proposed in 1986 by Catherine Browman of Haskins Laboratories and Louis M. Goldstein of Yale University and Haskins. The theory identifies theoretical discrepancies between phonetics and phonology and aims to unify the two by treating them as low- and high-dimensional descriptions of a single system.