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PROFESSOR: OK, I guess
we'll get started.

Last time, we were talking
about the auditory pathway

in the brain, the
central auditory pathway,

starting with the
cochlear nucleus

and going up through
the various brain

stem, the thalamic and
cortical auditory areas.

And then we focused mainly
on the cochlear nucleus,

which is the very first of those
many auditory central nuclei.

And we talked
about the diversity

of cell types or neuron
types in the cochlear nucleus

and the diversity
of response types

when you monitor the responses
of single neurons to sound.

And we did some attempts at
correlation between the two.

And those are firmly established
in the cochlear nucleus,

much better than anywhere
else in the auditory

pathways certainly.

So any questions from last time?

So today's lecture is on
hearing loss and implants that

restore our sense of hearing
if we happen to be deaf.

And I've written
a little summary

of what I want to cover
today on the board.

So we'll start out with the
first 2/3 of the lecture being

on hearing loss.

And we've mentioned a little
about the conductive apparatus,

the eardrum, the three
ossicles in the middle ear,

conveying the vibrations
to the inner ear.

And I think we had an example of
one type of conductive hearing

loss.

If you have, obviously, an
interruption of that ossicular

chain, then the
vibrations are going

to be reduced in the inner
ear in the conduction pah--

because the conduction
path is interrupted.

So those are relatively
straightforward concepts,

and so consider those covered.

Today, I want to talk
about the, perhaps,

more common types
of hearing loss

that are grouped under
the name sensorineural

because the sensory cells, or
the nerve fibers themselves,

are damaged.

And in that case, it's
not so easy to understand

how we might correct
them by putting

in an artificial middle ear
ossicle or something like that.

This is a bit of a misnomer
in that perhaps 99% of hearing

loss and deafness of
this type was really

based on the sensory
cells, so the hair cells

are the prime culprit in people
who have sensorineural hearing

loss.

The most vulnerable,
of the two types

of hair cells we've
been talking about,

are the outer hair cells.

Any of the various causes that
we'll talk about that damage

our hearing affect
the outer hair

cells to a much greater degree
than the inner hair cells,

and the reason for
that is not known.

For some reason, the outer
hair cells are more vulnerable.

As we'll see in the very first
slide of today's lecture,

those hair cells in the
basal turn of the cochlea

are more vulnerable than those
in more a apical regions.

Reason for that is
not known either.

It's a very interesting
phenomenon with no basis

that we know about.

We'll talk about permanent
and temporary hearing

loss, the various
causes of hearing loss,

and then, at the end, we'll
talk about the various neural

prostheses, or implants, that
are used to restore hearing.

And the most famous
of those, of course,

is the cochlear implant.

We hope to have a visit
from a subject who's

deaf, who uses a
cochlear implant,

and she'll be able to
demonstrate her implant to you

and answer questions if
you want to ask them of her

about her cochlear implant.

We'll also cover a couple
other different types

of implants that are
used to restore hearing.

So this first slide talks about
sensorineural hearing loss

in general.

And a very common pattern of
sensorineural hearing loss,

which comes from the basal
turn being most affected.

This is an audiogram,
if you will,

a graph of hearing level in
terms of sound pressure level,

hearing threshold as a function
of sound frequency for,

in this lower curve,
a normal hearing

human and, in this upper curve,
a typical pattern for someone

who has a mild to moderate
sensorineural hearing loss.

And so as you can
see, this individual

with the hearing loss has
perfectly normal hearing

thresholds up to the middle
frequency, 1,000 Hertz,

but then their
threshold of hearing

deviates from the normal so
that by about 10,000 Hertz,

they have a hearing
loss of 60 dB or so.

This is a very common
pattern of hearing loss that

arises because, for some
reason, the basal turn is

more affected.

The basal turn is where
you have the responses

to the very highest
sound frequencies.

This person will come into
the Massachussetts Eye and Ear

Infirmary, for example,
and complain to the doctors

and audiologists there when
the hearing loss becomes

noticeable, when they have a
problem understanding speech.

Hearing loss is
intimately entwined

with our perception and
understanding of speech.

And so when people have
problems understanding speech,

they often seek medical advice.

Now, the most important
frequencies for those in speech

are between about
300 and 4,000 Hertz.

So you can see this person's
hearing loss is clearly

getting into the
speech range, and they

may have problems discerning
the more high frequency

parts of speech.

So what are those?

So typically vowels, which
have the formants that we talk

about, have very low
frequency, so something

like ahhh and oooh.

They are very low frequencies.

But I think if you could read
this diagram a little better,

you'd understand that
high-pitched sounds

like the "sss" sound
of an s, or something

that has an abrupt
onset, like a "t",

has a lot of high
frequencies in that sound.

And so those are going to be
the first types of speech sounds

that are hard to
understand for the person

with the impaired graph
on the top slide there.

Now at first, you
might say, well,

what we should do is get a
hearing aid that amplifies

the frequencies that
are in loss area OK.

So to do that,
you'd have to have

a pretty sophisticated
hearing aid.

You'd have to, for
each sound frequency,

dial in the exact
amount of amplification.

And hearing aids are
very good these days,

and there are hearing aids
that can be used on a frequency

specific manner, that is
don't amplify anything

at low frequencies and amplify
exactly the amount of loss

at high frequencies.

So at first, it sounds
like a good idea,

but we'll get into the reason
that that doesn't always

work later on.

So that simple solution,
just install a hearing aid--

a hearing aid, which everybody
has seen one probably in older

people-- is simply an amplifier.

It has a microphone.

It picks up sound.

It boosts the sound
in whatever frequency

ranges the audiologist programs.

And then it has a little
speaker and it speaks or plays

the boosted sound into the
ear canal of the person.

So it's just an amplifier.

So you can have hearing
aids that work very well

and their frequency tailored.

And they especially
work very well

for the type of
hearing loss that's

called the conductive
hearing loss because, simply,

the problem is getting the
sound into the inner ear,

and amplifying the
sound, in a person

with a conductive hearing
loss, works very well.

It doesn't work so well
in sensorineural hearing

loss for reasons we'll
get into in a little bit.

Now how do these
hearing losses happen?

There are a variety of causes
that can damage your hearing.

We all have fun with sounds,
and we tend to have a lot of fun

when the sounds
are very intense.

And these are so-- this is an
old transparency obviously.

But this is a graph of
sound pressure level here.

Remember the thresholds of
hearing are way down here.

And these are some
example sounds

that have very high
level, and most of these

are damaging, at least if you
listen to them long enough.

Obviously, gunshots,
firecrackers are very damaging.

Those sounds are in
excess of 120 dB.

So a single gunshot, if
it's close to your head,

can be damaging.

So we had-- we're going
to have an example of that

in just a minute.

Some of these sounds
are more moderate,

around the region of 100 dB SPL,
for example, a chainsaw, a leaf

blower, the symphony
orchestra here.

So everybody goes to
the symphony, right?

So obviously,
these things depend

on how close you are
to the object that's

generating the sound, right?

So if you go to the
Boston Symphony,

you're not going to
endure a hearing loss.

But if you have good
seats and are looking down

on the symphony, you'll see
that a lot of the woodwind

players who are sitting
right in front of the brass,

for example, the
trumpet players, they

have a little
screen behind them,

a plexiglass screen that's
pretty invisible unless you're

looking for it.

That causes a sound shadow,
and so it protects their ears

from the blast of the bras.

And I've also been
in the symphony

where, sometimes, the woodwind
players would actually

put in ear plugs when
there's a big brass solo,

and brass is blowing like crazy.

And then after that big
solo, they take them out,

and they play their
own little solo.

So professional
musicians are obviously

very worried about
their hearing.

And it can be, if you're
close to a trumpet or a brass

instrument, deafening-- or
in front of a big timpani

or snare drums-- of
course, these things

depend on how long
you listen to them,

so the damage is cumulative.

It may take many years
of exposure at 90 dB

to produce a hearing
loss even though exposure

to a really high sound
level, like the 160 dB,

may give you hearing loss
after just a single exposure.

So legally, employers
are supposed

to provide hearing
protection for their workers

if you send a worker
in to an 85 dB

sound pressure level
environment, like is

common in a factory,
you are supposed

to provide the workers
with hearing protection

if it's an 8 hour shift.

If it's only a 4 hour
shift, you don't have to.

If the sound level is 95 dB,
it's something like 2 hours.

If it's 100 dB, you can expose
someone to an hour of that

without hearing protection,
but if it's longer than that,

you have to provide
hearing protection.

So here's some example.

Movie theaters,
Godzilla is 118 dB

because it's a terrible roar.

It can be deafening if you are
right near the loudspeaker.

And if you go to
Godzilla 100 times.

OK?

All right.

So loud sound is one of
the causes of hearing loss,

so let's just make
a little list here.

High level sound
is certainly one

of the causes of
hearing loss, and I

think we have some
examples here.

So this is an example
from some research that

was done by one of
the professors I had

in graduate school, Joe Hawkins.

And he studied
temporal bones where

the cochlear is in humans.

So he would get temporal bones
after a subject had passed away

and had donated their
body to science.

And they were useful if he knew
something about the individual,

like if they had
their hearing tested

or if you knew a little
bit about what activities

they liked.

These particular
data are from a human

who is an active hunter,
fired a gun a lot.

And the specimens shown
in the photomicrographs

here are looking
down onto the surface

of the inner ear, or
cochlea, on the left side

and the right side
of the subject.

The bone that's on the
snail shell, or cochlea,

has been thinned away
with a dental drill,

and you can see very
nicely the basal turn.

The apical turn, you can't
really see very well from that,

but you can thin the
apical turn as well.

Sometimes.

It's cut off and thinned
in a different dish.

But anyway, what you're
looking at here--

I should get out my pointer,
so I point a little better.

So this is the very basal end
of the cochlea and spiraling up.

And the human has about 2
and 1/2 or 3 complete turns

of the cochlea.

And this white structure
here is the organ

of Corti sitting on
the basilar membrane.

This specimen is stained with
a stain called osmium, which

stains lipids and especially
myelinated nerve fibers,

so you can see a lot of
myelinated nerve fibers.

They looks like
threads coming out.

And here's some more
threads up here.

And I said the organ
of Corti is here,

but actually, it's completely
gone here on the left side,

and you can see it
begin right about here

and go apically here up
into the apical turn.

You can see a very
little bit of it

in the extreme basal
part of the cochlea,

and that's diagrammed
here on this graph.

This is the length along
the basilar membrane

from the base over here
on the right to the apex.

And this y-axis graphs the
percent of the hair cells

that are remaining.

And in the basal
turn, they're almost

zero hair cells remaining.

They're all gone.

Maybe a couple little
islands here and there,

but it's virtually
100% hair cell loss.

And as you go around
the upper basal turn,

you have most of the
hair cells remaining

in the case of the solid line,
which refers to the inner hair

cells.

And then you have, in the
dashed lines, the three

rows of outer hair
cells, and there, maybe

between 30% and 70%
remaining depending

exactly where you are.

But here again, something
has damaged these hair cells,

completely wiped them out in
the basal half of the cochlea.

And wiped a lot of
the outer hair cells

out and not very many of the
inner hair cells are wiped out.

Here's the subject's
right cochlea.

And in this case, you
can see-- you don't even

need the graph-- you can
see that the organ of Corti

is pretty intact.

Here is a little island
of loss, and then

another little island
of loss, but then you

have an intact organ of Corti
all the way up to the apex,

and that's reflected in the
counts here where you have,

except at the very basal
part of the cochlea which

doesn't appear in
the micrograph,

you have a pretty normal
complement of inner hair cells.

Outer hair cells are
not in such good shape,

but they're present throughout
the cochlea in this right side.

Now, also on here are
graphs of the nerve fibers.

Those are these little
thread-like stained elements

here that appear very
nicely in this osmium stain,

and they're pretty much
intact through the cochlea.

Maybe in places here where the
hair cell loss is really bad,

some of the nerve
fibers are gone,

and that's indicated by
this interruption here.

But this is another
example where

you can have whatever damaged
this fellow's hair cells, left

the nerve fibers
relatively intact.

And this offers some
hope to somebody

who wants to install a
prosthesis like the cochlear

implant and stimulate the
remaining nerve fiber just

because they're
going to stick around

even if a lot of the
hair cells are gone.

So this subject, as I said,
was an enthusiastic hunter,

and a he was right-handed.

And as you can see
right here, this

is a top view of a
person firing a rifle.

The left ear of the
subject is pointed

toward the tip of
the gun, and that's

where the bullet
emerges, and that's

where the shock wave of
the rifle, when it fires,

comes out.

This is a modern rifle,
not a flintlock rifle

where you have a lot of smoke
and sound coming out down here.

Most of the sound comes
at the tip of the gun.

And this subject's left ear
is pointed right to that

and has taken the
brunt of the blast

in terms of the
loss of hair cells.

The right ear of the
subject is pointed more away

from the tip of the
gun and is protected

and has a pretty normal
complement of hair cells.

Now, that's not saying
that this person didn't

go to lots of rock
concerts, and didn't

take lots of drugs that
damage your hearing,

and isn't an 80-year-old
person, so we're

going to add a few
things to our list here.

There are some drugs, for
example aminoglycoside

antibiotics-- they are
really great antibiotics,

but they have this side effect
of damaging the hair cells.

Three, the aging
process damages hearing.

And in this kind of a study
where you're using a human,

you cannot control for these
other factors and others that I

haven't, but what you can do
then is compare left to right.

Because presumably,
a subject took drugs,

and they appeared in both the
left and right in your ears.

And obviously, the
subject had the same aging

in the left and right side,
so whatever differences there

are between the
left and the right,

we attribute then to
the blast from the rifle

that the subject shot.

So this cause of
left right difference

would be attributed to
the high level sound.

Here are some pictures
from an experiment animal

that has undergone a high sound
level, or an overexposure.

This is a normal-- I
think, in this case,

it's a Guinea pig cochlea.

And you see the row of
inner hair cells here.

There is 1, 2, 3, 4, 5, about
a dozen inner hair cells.

That's just one row
of inner hair cells.

And then there are three rows
of outer hair cells looking down

onto the tops of
the hair cells where

you have the stereocilia
sticking up at you.

And there are 12 or
15 outer hair cells

in each of rows 1, 2, and 3.

And it's such a regular pattern,
and they're all perfectly

there.

After listening to the
overexposure of sound,

there are quite a few
inner hair cells lost.

Those that are
remaining sometimes

have abnormal stereocilia.

There are number of outer
hair cells, in this case,

in row one lost.

And some that are remaining
are indicated by these arrows

to have abnormal stereocilia.

And here's another example
from a different place

in the cochlea where almost the
entire third row of outer hair

cells is wiped out by the
overexposure to noise.

So what happens when
you lose a hair cell?

Well, the nearby supporting
cells go fill in its space,

and they take over.

In mammals, such
damage is permanent.

Once the hair cell is
killed, it never grows back.

And there's a lot of
interest in trying

to coax the nearby
supporting cells

to, in these damage
cochleas, become hair cells.

But so far that has
not been possible.

The field was really
excited about 20 years ago

when this type of damage
in a bird cochlea,

if left for a month
or so, you see

reemerging small hair cells.

And if you wait long enough,
they become full hair cells.

In the bird cochlea, the
surrounding supporting cells,

after damage to the hair cells,
can then divide and become

new hair cells, in the
chicken cochlea, for example.

And this was a
serendipitous discovery

where people were working on
damaging chicken hair cells,

and they were always waiting a
couple days after the exposure

to look at the cochleas.

And there was a holiday vacation
where they exposed the animals

before, and they
went out of town

and came back three
weeks later, and they

found something must have
gone wrong with the exposure

because the hair cells are here.

They're fine.

But they figured out
later that, actually,

the supporting cells
nearby had grown back.

So that doesn't seem to help
us in the mammalian pathway.

There's some sort of
growth factor or growth

pathway in birds where
these hair cells grow back,

but not in the
mammal unfortunately.

So this is an example
from a cochlea that's

been treated by
an aminoglycoside,

and this is just to
remind me to tell you

that, once again, you can count
hair cells along the cochlea.

This is a plot of
hair cells present

where lots of black bars
means lots of hair cells.

And this is a beautiful
example of this particular drug

treatment, which I
believe is kanamycin,

and a certain dose doesn't
affect the inner hair cells

at all.

But look at the
outer hair cell loss

in the basal part of the
cochlea, virtually complete

outer hair cell loss showing
that the outer hair cells are

more sensitive, they're more
labile to this drug treatment

than are the inner hair cells.

And once again, the most
vulnerable part of the cochlea

is not the apex.

0% distance from
the apex is up here.

And the basal region
would be down here,

and that's again the
most vulnerable part

of the cochlear for some reason.

We can speculate
about why this might

be the case for drug treatment.

We don't know this,
but maybe the drug

appears in more in a
higher concentration

in the basal part
of the cochlea.

In the cochlea, like
you have in the brain,

you have a blood-brain barrier.

You have a
blood-cochlea barrier.

Obviously, some drug has
gotten into the cochlea,

but maybe the
blood-cochlea barrier

is more permeable
down here in the base.

And in the apex not
as much drug got in.

That's an idea.

It hasn't been borne out
by experimental evidence,

but it's an idea that
people have in mind.

Or, it could be
that the outer hair

cells are just, for some reason,
easier to kill in the base.

That's more suggestive
that all of these things

affect the hair cells in
the base more than the apex.

Now, these were some of the
original experiments that

showed what outer hair cells did
for us in the sense of hearing.

So earlier in this
course, we had the effect

of knocking out the
outer hair cells

by knocking out the
gene for Prestin.

OK?

In this case, the
outer hair cells

are knocked out by
the drug treatment.

So you've lesioned
the outer hair cells

in the very basal
part of the cochlea.

The inner hair
cells are present.

Let's look at the tuning
curves from auditory nerve

fibers in that preparation.

Now let me remind you again
what's happening here.

So you have the
inner hair cells,

and you have the
outer hair cells,

which have been killed
by the drug treatment.

And then you have most of the
auditory nerve fibers coming

from the inner hair cells
in the auditory nerve going

to the brain.

And the experiment then is to
if you're recording electrodes,

record from the
auditory nerve fibers,

get a single nerve fiber,
and take its tuning curve.

And that's what's shown
on this top graph.

So tuning curves from the
normal region of the cochlea

are normal shaped.

They have sharp tips and
tails, normal sensitivity.

In the region of the cochlea
when the drug treatment has

lesioned the outer hair
cells, the tuning curves

look extremely abnormal.

There's a tail, whatever tip
there is is a tiny little tip,

and there's a tremendous loss
of sensitivity, as much as 60

or more dB lost.

Basically, these are
tipless tuning curves.

And now we know that
the outer hair cells

have their
electromotility function.

They are the cochlea amplifier.

Without the amplifier, you lose
the tip on the tuning curve.

So that should be a mini review.

This is the way the outer
hair cells originally

thought-- or discovered
to be important

in the sense of
hearing, to provide

the normal sensitivity
and a sharp tuning.

You can get all kinds of tuning
curve abnormalities depending

on whether you, in this case,
lose all the outer hair cells.

You cause disarray
of the stereocilia.

You have partial loss
of the outer hair cells.

All these kinds of things can
be found after noise damage

depending on the place of
the cochlea you look at,

the type of noise, the
length of the noise exposure,

and the animal.

There's a lot of variability
in noise damage from exposures

to 10-- 10 different
animals, you

can have 10 different types
of loss of hair cells.

Noise damage is
tremendously variable

from subject to subject.

Now, we also had--
this is another review.

We also had the example of a
psychophycial tuning curve.

So this is a normal
psychophysical tuning curve.

Can somebody explain to
me what the paradigm is?

A psychophysical
tuning curve, it's

taken from a human
listener, right?

What's the paradigm?

We had this in class, so we
should all know what this is.

A psychophysical tuning
curve, you have a probe tone.

I think that, in this
case, the probe tone

is right at the
tip of the arrow.

And the subject is instructed
to listen to the probe tone

and say when you
hear the probe tone.

Give the probe tone.

Yes, I hear that definitely.

Give it again.

Oh, yes, I hear that.

No problem.

Then, you add a second tone,
maybe a little bit higher

in frequency than
the probe tone.

Probe tone was-- let's say,
in this case, 1 kilohertz.

The second tone, masker tone
is 1.5 kilohertz, let's say.

Introduce that.

Person, yeah, I still
hear the probe tone.

I hear this other tone too.

Oh, don't pay attention to that.

Just listen to the probe tone.

Sure, I hear that.

Then, you boost the level
of that second masker tone

up to, in this case, 90 dB.

The person says, I can't
hear that probe tone anymore.

Can you turn it up?

And you plot that on your graph.

That's a hit.

That's a point.

In that case, the masker has
made inaudible the probe.

And you go on varying your
frequencies and levels

until that masker masks
the probe and the person

says I can't hear
the probe anymore.

And you get the so-called
psychophysical tuning curve,

which has this
very nice tip to it

and a long low frequency tail
from a normal hearing person.

But a person with a
sensorineural hearing loss

often has a psychophysical
tuning curve like this.

This should remind you
of the tuning curves

that we just saw from
auditory nerve fibers

in the damaged cochlea, which
is basically a tipless tuning

curve.

Perhaps in this case,
the outer hair cells

have been damaged
by fun with sounds,

and you have just the
tail of the tuning curve.

Now, here we come
to the crux of why,

in this person who has
a sensorineural hearing

loss-- they still
have hearing, but they

have a big loss-- why won't
just a hearing aid work?

You can certainly
install a hearing aid

into this person's ear canal
and boost their threshold

from what they used
to here down at 0

dB to what they
now here at 60 dB

You can amplify
the sound at 60 dB.

OK, fine.

Then, they'll start to say,
yeah, I here it no problem.

What happens when this person
goes to a crowded restaurant,

and there's all this
low frequency DIN?

Well before, all the low
frequency DIN was here.

It didn't get into
the response area

of the sharply
tuned tuning curve.

Now, you have all
this low frequencies

that's amplified
by the hearing aid.

It now gets into the response
area of the nerve fiber.

That low frequency
signal, which you

don't want to pay attention
to because you're listening

at 1 kilohertz, is a
competing, or masking, stimulus

along with the signal.

And so now, the person with the
hearing aid and sensorineural

hearing loss goes into
the crowded restaurant

and says I hear very well, but
I can't understand the person

across the table speaking to me.

All I hear is this big noise.

And no matter what I-- how
I adjust my hearing aid,

it just sounds noisy.

I can't understand anymore.

I can hear.

They're certainly not deaf, but
they can't understand anymore

because before they had
sharply tuned frequency tuning,

and now they have no
frequency tuning at all.

It's very broad.

That's the problem
that a hearing aid

can't deal with in terms
of restoring normal hearing

to a person with
sensorineural hearing loss.

Before I start to
talk about implants,

let me just remember to say
what other processes affect

our hearing.

And we have a list just so
I don't forget anything.

And one of the important
things is genetic causes.

So maybe you can't see that
from the back of the room,

but number four here
is genetic causes.

There are babies
who are born deaf,

and in the state of
Massachusetts, in most states,

it's mandatory to test infant
hearing at birth because you

want to install a hearing
aid or install a cochlea

implant at a young age if
the baby has hearing loss.

And another cause
that we should list

are certain kinds of infections
and disease processes.

Number five, cause of hearing
loss is diseases, for example,

meningitis.

And one of the MIT
students that I

used to use for demonstration
of cochlea implant

is deaf because at age 12, he
got very sick with meningitis.

And when I asked him,
how did you go deaf?

He said, well, I got
sick with meningitis.

And I was so sick that my MD's
treated me with aminoglycosides

so that they would kill
the meningitis bacteria.

And he isn't sure whether it's
the meningitis or the side

effect of the aminoglycosides
that made him deaf.

But when you woke up, he
was cured, but he was deaf.

So in some cases you're not
sure which of these agents

caused the hearing loss.

So that's a pretty
complete list now.

Do we have any questions about
what things cause hearing loss?

And you might imagine
that, during our lifetime,

some of these things will be
understood in a better way.

It's clear why loud sound
causes hearing loss.

I mean the mechanical action.

These things are moving.

You could damage the
very sensitive apparatus,

like the stereocilia.

Drugs, aminoglycosides
bind to some

of the membrane
channels in hair cells.

And maybe a therapy for this
ototoxicity, this hearing loss

created by these
aminoglycosides,

could be to install some
competitive binder that

would occupy the binding
sites while you gave the drug

therapy.

We don't know at all what causes
the hearing loss with aging.

That's a very active
subject in today's research.

Genetic causes, same
way, usually these

are some sort of developmental
factor or protein

that's necessary for normal hair
cell development and it's lost,

in the case of recessive
genetic problem.

That's pretty clear
how that arises.

Meningitis, it's not clear how
those diseases kill hair cells,

but they certainly do.

But there's certainly
room to imagine

that will be worked on quite
actively in the next 10

or 20 years.

It's not known right
now how the hair

cells are lost in meningitis.

So let's talk about, now, people
who have complete hearing loss

and are eligible for
the so-called cochlear

implants and other types of
implants that restore hearing.

So this is a nice
slide from, I think,

the paper that we're
reading for today.

And actually that reminds
me, besides that paper, which

is a very short
one, easy to read,

the textbook reading
that I've assigned

for today, which
is most of chapter

8 on auditory
prostheses is excellent.

It's really up to date.

It tells you a lot
about cochlear implants

and coding for speech,
which I probably

won't have time to get into.

But this is a really-- I mean
hearing aids past and present,

that's not so important.

But it has a lot
of good information

on cochlear implants, so
I'd encourage you definitely

to read that textbook
passage today.

And the research report
by Moore and Shannon

is a very simple,
easy to read paper.

It shows you the sites where
these various implants go.

So the cochlear
implant, obviously,

is installed into the
cochlea, right here.

For people who have lost their
hearing because of a problem

with their auditory nerve,
you put a cochlear implant in,

and it's not going to do any
good because the messages

aren't going to be conveyed
by the nerve into the brain.

And so what's an example
of someone like that?

Well, a disease process
called neurofibromatosis

type two, or NF2, is a disease
process where the subjects get

tumors that grow
on various nerves.

And a very common type
of tumor in NF2 patients

is called a
vestibular schwannoma.

And a schwannoma is a
tumor of the schwann cells

that normally provide the myelin
covering of peripheral nerves.

And it grows on the
vestibular branch

of the eighth cranial nerve.

Obviously, that's quite
near the auditory branch

of the eighth cranial nerve.

And these tumors grow and grow.

They probably rob the
nerve of the blood supply.

They probably put
pressure on it,

and they certainly
infiltrate the tumor cells

in amongst the fibers.

And when the surgeon goes in
to remove that type of tumor

invariably the eighth
cranial nerve is cut.

So in that case, the subject
has no nerve conveying messages

from the cochlea into the brain.

Well, the surgery is right here.

You're removing a
tumor from here,

so it's fairly easy to go
ahead and install an implant

into the cochlear
nucleus of the brain.

The cochlear nucleus is visible.

And that's what's called an
auditory brainstem implant.

It should be called a
cochlear nucleus implant,

but it's called an ABI.

And an ABI-- I'm not going
to talk too much about it--

but just suffice it to say, it's
an array of surface electrodes.

There are two
companies making these.

One has 15, and one has 21
in a checkerboard pattern.

And the electrodes go onto
the surface of the cochlear

nucleus, and their placed
there during the surgery.

There was an experimental
penetrating electrode array,

or PABI, but that's
been discontinued

because of side effects.

Some of these patients
got trigeminal neuralgia,

or pain sensations from nearby
nerves, maybe by the fact

that these electrodes
penetrated into the brain.

And so that underwent
an FDA trial,

but that's no longer used.

But this surface ABI electrode
is used in cases of NF2

or in other cases where the
nerve function is compromised.

Those implants don't
work very well.

So if you look at
this graph here.

This is a graph of the
different types of implants,

especially I'll call your
attention to the cochlear

implant and the auditory
brain stem implant.

In the cochlear
implant, you've got

a lot of people who can-- if you
do in a word recognition test,

how often they get the
words correct, a lot of them

are placing at
100% of the words.

So the task here is you
stand behind the subject,

or the audiologist stand
behind the subject,

and they say repeat
after me, baby.

And the person says baby.

Sunshine, and the
person says sunshine.

And the person says, Red Socks.

And you say, Cardinals.

And they got one wrong.

But anyway, you
can do these tests

without-- it's important
to stand behind the person

to make sure they're
not lipreading.

But a lot of cochlear
implant users

can get 100% on these tests.

Now, the ABI, auditory
brain stem implants,

you've got many of the
subject, if not all of them,

saying the wrong word or not
giving you any response here.

So what good is the ABI?

The real success story
of these prostheses

is that the person
can understand speech.

If the person can't
understand speech,

this thing isn't doing
them too much good.

So that's not to say
that the ABI isn't

successful in certain ways.

The ABI is sometimes thought of
as a lipreading assist device.

So it helps these
subjects read lips better.

For example, if
you guys are deaf

and you look at my letters, and
I make two different sounds,

pa and ba.

That looks exactly the same if
you're trying to read my lips.

But it sounds different to you.

You guys have good
hearing, and it

may sound a little bit
different to the ABI user,

and it may give that ABI user
a little bit of a step up

and help versus someone
who's just using lipreading.

Now, just for
completeness, I'll talk

about the auditory
midbrain implant.

The idea here is to put
the implant higher up

in the pathway.

Why would you want to do that?

Well, some people
think that the ABI

doesn't work because there's
been this tumor here.

And surgeon has been hacking on
the tumor to try to get it out,

yanking and pulling on it.

If the tumor didn't damage
the cochlear nucleus,

well, the hacking and
tugging on it did.

And so maybe you
should put the implant

further up where
you haven't been

hacking and everything's normal.

And so that's the idea behind
the auditory midbrain implant,

which goes into the
inferior colliculus.

And there have
been five patients

who've gone undergone
the auditory midbrain

implant-- actually six,
five very well documented.

And the outcomes have been
no better than the ABI,

but that's because four out
of the five well-documented

didn't hit the right spot.

The inferior colliculus
is pretty small,

and the part that you
really want to go into

is the tonotopically
organized spot

so that this needle
electrode y--

this is a long electrode
array with about 16 contacts

on it, in this needle.

And that's put into the
tonotopic part of the IC,

and it didn't get into the
right place in most people.

But even in the one individual,
got it in the right place,

it wasn't any
better than the ABI.

But there is going to be another
clinical trial in which they

implant five more subjects.

And hopefully, the outcomes
will be better on that.

So that's the various
types of electrodes.

And, obviously, the
cochlear implant

is the real winner here.

And we have been having
readings-- Hi, Sheila-- we've

been having readings
in our class,

and I'll do a reading now
about the cochlear implant.

This is from-- this is
not made into a book form

yet because this is from the
esteemed academic publication

called Yahoo
Finance, on the web.

And this is dated
September 9, 2013.

And the subject of this
column is the Lasker Award.

So the Lasker
Award, does anybody

know what the Lasker Award is?

Sometimes, called the
American Nobel Prize,

so it's a very
prestigious honor.

It's given in several
different fields,

mostly in medicine
and biomedical areas,

and so there are sub-groups.

And this one was given in
clinical medical research

award.

So the 2013 Lasker Clinical
Medical Research Award

honors Graeme Clark, Ingeborg
Hochmair and Blake Wilson

for developing the modern
cochlear implant, a device that

bestows hearing on
profoundly deaf people.

The apparatus has,
for the first time,

substantially
restored a human sense

with a medical intervention.

Blah, blah, blah.

Throughout the world today,
there are about 320,000 people

outfitted with
cochlear implants.

Most recipients can
talk on their cellphones

and follow conversations in
relatively quiet environments,

and an increasing
number of patients

with severe age-related
hearing loss

are taking advantage of
this marvelous invention.

So the three people
here, two of them

are actually founders of
cochlear implant companies.

So you can think of Nobel Prizes
and these prize being awarded

to people who made
big discoveries.

And certainly, in the third
case, Blake Wilson did.

But in the first two, it's
really conveying a technology

to the masses that was
recognized by this award.

So that's the 2013 Lasker Award.

So let's look a little bit about
what a cochlear implant is,

and that's shown in the
next couple of slides.

So the cochlear implant
has an internal part, which

is a series of electrodes
that go into the cochlea,

and the electrode
comes out from here

and goes into a
so-called internal coil--

sorry about that-- and this is
sometimes called the receiver

because it gets messages
from the external coil,

or sometimes called the
transmitter, across the skin

here.

So there's skin between the
external and internal coils.

On the outside, you
have a microphone

which picks up the sound and
sends the microphone messages

to a so-called speech processor.

The speech processor
sends transforms

that sound wave form into a
series of electrical pulses

that are sent down
the electrodes

and stimulate the
remaining auditory nerve

fibers in the cochlea.

So the cochlear implant has the
electrodes, the internal part,

the external part, and
the speech processor

and microphone.

And I have a demonstration
cochlear implant here.

And I'm going to pass it around.

These things are very valuable,
so as demonstration models,

they strip off the electrodes.

So the part I'm
passing around is just

this tube that goes
down here but not

the electrodes
themselves, and I think

it has the internal and
external coil, and obviously not

the microphone or
the speech processor,

so just to give you
an idea of the size.

And I think this one,
the tube comes down,

and it coils around a
little like the electrodes

do as they coil in the cochlea.

Now, this next slide
is pretty important

because it shows the
electrodes coming

into the cochlea in
a cutaway diagram.

And so the electrodes come in
the basal turn of the cochlea.

Remember there's an
area in the bone that

has a little membrane over
it called the round window.

Surgeons can go in there and
make a tear in round window

and put the implant in there.

Or, they can drill
a hole a little bit

apical from the round
window and start

in the base of
the cochlea, which

is the big part of
the cochlea and then

thread just by pushing
the electrode array more

and more apical
into the cochlea.

Now, the cochlea gets pretty
small as it goes very apically.

And the electrodes don't fit
into the apical region so far.

So current cochlear
implants only

can be pushed in about to cover
the basal half of the cochlea,

the basal 50%.

So that seems like
a huge limitation.

It's a bit of a limitation.

Fortunately, it's not
an extreme limitation

because the spiral ganglion
doesn't go all the way

to the apical part
of the cochlea.

The ganglion is where the cell
bodies of the auditory nerve

is.

And so there is ganglion that
ends about 3/4 of the way out,

so the last quarter
wouldn't be helpful anyway.

And here are the
various electrodes

along the cochlear implant.

And modern cochlear
implants have 22 electrodes.

And they are hooked up.

I'll show you how they're
hooked up in just a minute.

Actually, I'll show you how
they're hooked up right now.

The way this works is
the microphone signal

comes into the speech
processor here,

and the microphone signal is
split up into various bands.

The microphone might pick
up only high frequency,

in which case, this
band would be active,

or it might pick up middle
frequencies, in which case

these bands would be active, or
it might pick up low frequency

or it might pick
up all frequencies.

It depends on what the sound is.

The output of those filters
is sent to some processing

schemes, which eventually result
in little electric pulses,

and those are shocks
that are sent down

into the cochlear
implant electrodes.

And this is supposed
to be-- actually

something's not happening
here automatically.

This is supposed to be
electrode number one, which

is the most apical electrode,
and so on and so forth.

And this scheme only
ends in electrode 18,

so this is an old diagram
here because current cochlear

implants have 22.

So if you are hearing
very low frequencies,

you're going to be stimulating
very apical electrodes.

And if you're hearing
the highest frequencies,

you're going to stimulate
the most basal electrode.

And this is a recapitulation
of the place code

for sound frequency where base
of the cochlear transduces

in normal hearing, the high
frequencies, and the apex

transduces the low frequencies.

So when we said the
cochlear implant doesn't

go all the way apically,
it can't fit there.

So what happens?

Well, the apex isn't
very well-stimulated

in these designs.

And so you will
hear descriptions

of people who have their implant
turned on for the first time,

and they'll say it
sounds like Donald Duck.

It sounds really shrill
and very high-pitched.

Well, a lot of the apex-- not
drawn here-- is not stimulated.

So what happens?

So these people,
after a month or two,

say oh, yeah, it's
sounding better and better.

And so there's some sort
of learning or plasticity

that makes things settle
down, and the voices

sound a little bit more
normal, maybe not normal,

but more normal.

And perfectly, as you saw
from the graph before,

normal word
recognition scores can

be achieved even though
you're stimulating

just a portion of the cochlea.

Now, I have a movie here,
and this gets on my nerves,

but I want to show it
to you because this

is what's shown to
patients who are

about to get a cochlear implant.

Gets on my nerves because you
see hair cells in here that

have stereocilia that
are just waving around,

but the stereocilia
are really rigid.

But anyway, I thought it
would be interesting just

to see what someone sees
when they are getting

this stuff from a
cochlear implant.

Let's see if this
movie will play.

[VIDEO PLAYBACK]
In normal hearing,

the hair in the inner ear--

PROFESSOR: I hate this.

I mean the best
membranes way over here.

The hair cells--

-The hearing nerve still
remains functional,

but the hair cells have
been lost or damaged.

In a cochlear implant system,
sound enters a microphone

and travels to an
external mini computer

called a sound processor.

The sound is processed
and converted

into digital information.

This digital information is
sent over a transmitter antenna

to the surgically implanted
part of the system.

The implant will turn
the sound information

into electrical signals
that travel down

to an electrode array inserted
into the tiny inner ear.

The electrodes directly
stimulate the auditory nerve,

sending sound
information to the brain.

Bypassing the damaged inner
ear, the cochlear implant

provides an entirely new
mechanism for hearing.

[END VIDEO PLAYBACK]

PROFESSOR: So that's
what the patient's see.

And how well does it work?

So we can ask a demonstrator
that we have today.

Sheila come on up in
front of the class.

This is Sheila [? Zu ?],
who is a MIT undergraduate.

You're a senior now, right?

What's your major at MIT?

SHEILA: I'm the only
in this major at MIT.

I'm in [INAUDIBLE]
technology and [? society ?]

and [INAUDIBLE] is a joint
major between Humanities

and [? Chinese. ?]

PROFESSOR: Are you
an overachiever?

SHEILA: I don't know.

Maybe.

PROFESSOR: So has
anybody in the class

ever spoken to a cochlear
implant user before?

SHEILA: I know some of them.

PROFESSOR: You know
some of these people?

SHEILA: We're in the same dorm.
[INAUDIBLE] in my sorority.

OK.

Great!

So we can do this
whatever way you want to.

You can ask Sheila
questions if you've already

asked them to her.

I'll ask her questions.

Does anybody have any questions?

Yes?

AUDIENCE: How old were you
when you got your implant?

SHEILA: So I was born
deaf, but I got implant

when I was 3 years old.

Actually, I got surgery
when I was 2 years old.

[INAUDIBLE] when
I was 3 years old.

PROFESSOR: So one
question I often

get about implants into children
is how young can a child be

and still be implanted
successfully.

So the surgeons at
Mass Eye and Ear

say that the cochlea is
adult size by age 1 and 1/2,

so typically, that's the age
when a person who is born deaf

is implanted these
days, age 1 and 1/2.

The idea to implant early
is so that the subject

can grow up and enjoy
normal hearing, especially

during a critical period for
language formation, which

was maybe starting at
1 and 1/2, 2 years old.

So if you implant a person
later, in their teens,

and they haven't
heard sound, they

have a lot worse chances of
acquiring normal language

skills than someone like Sheila
who has been implanted early.

So the trend is to try to
implant as early as possible.

SHEILA: I want to point out that
I may have been implanted when

I was 3 years old,
but I didn't start

speaking until I was
about 5 years old.

And I didn't start
learning math or learning

how to read until I was 7
years old, so I was really

delayed back then.

PROFESSOR: Did you
have a question?

AUDIENCE: So I was
just wondering, are you

like reading my lips right now?

SHEILA: Yes, I am.

So the way it works, I
have to see people's face,

like how to read their lips, and
I listen too at the same time.

I could read your lips alone,
but maybe not 100% accurate.

Or, if I don't look at you
lip, and listen to you,

maybe not really
understandable, so it's

like I have to read lips
and listen at the same time

in order to understand you.

PROFESSOR: But if you don't
read lips, for example,

in situations like
talking on the telephone,

can you understand
someone on the telephone?

SHEILA: It depends
on the person.

If I'm familiar with your voice,
like I know my dad's voice.

I can understand
him pretty well,

but if I'm talking to a stranger
on the phone, then maybe not.

And also, don't forget, there's
a lot of background noises,

so that makes it harder for me
to hear people on the phone.

PROFESSOR: When I-- let's say
about 10 years ago in my lab,

I hired a research assistant
who used a cochlear implant,

and she wanted me to
shave off my mustache.

It was because she had
a little trouble reading

my lips with my mustache.

Now, my wife also has told
me I should shave a mustache,

but she has normal hearing.

SHEILA: I actually
had a professor at MIT

when I was a freshman,
I comment one day I

had hard time understanding
him because he

had like a full beard.

Then, next day, he
shaved off everything.

So he came up to me, I
was like, who are you?

[INAUDIBLE]

PROFESSOR: That's very nice.

Wow, interesting!

I didn't shave off my mustache,
neither for my assistant,

nor for my wife.

SHEILA: [INAUDIBLE]
half is better.

PROFESSOR: Maybe.

Yeah.

So if an audiologist were to
test your speech comprehension,

do you think you'd
get every word correct

or do you think you'd miss some?

SHEILA: I think I
probably miss some words

or may not pronounce
some words correctly,

because the way I hear
words may sound differently

from what you hear.

And sometimes, in
English language,

some words don't sound exactly
the way it's written down.

So I think my speech is
not bad because, based

on my interaction
with people, they

seem to understand
me most of the time.

Yeah?

AUDIENCE: Do you know
any other languages?

SHEILA: I know another language.

Yeah.

I know a couple of languages.

I know American sign language.

I use it often to
help, in some cases,

when cochlear
implant don't work.

For example, if I'm
in a loud bar or party

and I can't hear people,
but if I use sign language,

I understand people.

I know British
sign language too,

but that's another
sign language.

PROFESSOR: So you mentioned
when you're in a party

and you can't hear people,
does that mean that there's

a lot of noise that
masks speakers and that's

a hard situation for you?

Right.

SHEILA: So like
the speaker's voice

will blend into other speakers
voices or background noises,

so I tend to rely on
lipreading or some other method

to communicate.

PROFESSOR: Right.

So for example, in
cochlear implants,

a common problem is when
there is an environment where

there's many, many
frequencies of sound,

like a crowded
restaurant or a party,

and there's one speaker that
you're trying to pay attention

to and the subject
gets overloaded

on every single electrode.

And so some kinds of
cochlear implant processors

try to circumvent that by trying
to pick out in the spectrum

the important peaks
of the spectrum.

So if you're listening
to the vowel aa,

you'd have three formants.

The processor tries to pick
out those formants and only

present electrodes
corresponding to those formants

and turn all the other
electrodes off so that there's

a huge difference between
where the formant is

and where the nothing is.

Really in theory, it's
nothing, but actually, it

could be a noisy background.

So that is one kind of
speech processor design.

It's called the speech
feature extractor, sometimes

the speak chip.

It's trying to pick
out formants so

that it can understand vowels.

And it's supposed to be less
sensitive to noise masking,

which is a huge problem
in cochlear implants.

A cochlear implant user doesn't
have the sharply tuned filter

of the normal
auditory nerve tuning

curve that normal
hearing people do.

What about listening to music?

Do you listen to music?

SHEILA: Yeah.

Like last month, I went
to hear Yo-Yo Ma play.

Like when-- I can hear
music, but I'm not sure.

I think I hear music
differently from you guys

because there's a whole
range of frequencies,

like you said, but yeah
I can listen to music.

AUDIENCE: How often do you
go to the doctor for updates?

SHEILA: How often do I go to--

AUDIENCE: You're doctor.

SHEILA: Oh, you
mean audiologist.

I see audiologist like
maybe once every year just

for a checkup and remapping.

PROFESSOR: So do
you get a remapping

or do they just bill
your insurance company?

SHEILA: Yeah.

PROFESSOR: Yes.

SHEILA: It's expensive.

PROFESSOR: But do
they-- do you know

if they change the mapping
for your electrodes?

SHEILA: Yeah, they change
it, but they told me

it's not really
a lot of changes.

So I think the older
you get, the less change

is made than when
you were younger.

PROFESSOR: Perhaps, yeah.

So that's interesting.

So how do they do that mapping?

Do they say here's electrode
1, and then here's electrode 2.

Which is higher?

Do they do that?

SHEILA: Yeah, so I had to go
into a special sound booth.

So it's like a cell that
is completely soundproof.

And they will test me
on a bunch of sounds

like saying stop
if it's too loud,

or which one is
louder or softer,

can you repeat words
after me, and so on.

And they use all of that
input to create a new map.

PROFESSOR: Interesting.

So apparently with
cochlear implant users,

the frequency mapping
of the electrodes

doesn't change in a big way.

But in the auditory
brain stem implant,

they go through yearly checkups
and, evidently, the mapping

can change a great deal.

So it's completely different.

In cochlear implants, usually
the most apical electrode

evokes the lowest
sensation of pitch

and more basal electrodes get
higher and higher sensations

of pitch.

AUDIENCE: How easy is it
for you to differentiate

between two voices?

Like if you didn't see who was
talking and if I said something

and then Professor
[? Brown ?] said something,

how different would our
voices sound to you?

SHEILA: His voice is deeper,
and you're farther away from me.

So I think I can tell the
difference between you two.

I can tell difference between
male and female voices.

PROFESSOR: Right.

Female voices sound
higher usually.

SHEILA: Higher pictched.

Yeah.

PROFESSOR: Do you
know Mandarin Chinese?

SHEILA: Yeah, a little bit.

I can speak some
Chinese, but not

so good because I haven't
used Chinese for a long time.

PROFESSOR: It's a
tonal language, right?

SHEILA: Yeah.

Oh my God!

PROFESSOR: Does that give you--

SHEILA: It's like I went
to China 4 years ago.

I stayed in China
for about a month.

So my grandma,
she couldn't speak

English, so I had to
speak to her in Chinese.

But it's interesting how
it's-- when I talk to people,

like when I speak myself, I have
to remember how use the tones,

but if I listen to them, I can't
tell the difference between

tone.

So what I do is I read
their lips and listen.

And I use context clues
like so if the sound goes

with this sound,
so I think those

sounds form a certain word.

That's how I did,
but I believe I

can learn Chinese with
a matter of practice

and getting used to the sound.

PROFESSOR: Apparently,
cochlear implant users

have a lot of problems
with melodic intervals,

octave matches, and
tonal languages.

The temporal code
for frequency that

helps us appreciate
musical intervals

is not present at all
in any cochlear implant

scheme that's used now.

So you only have the place
code for sound frequencies,

you don't have the timing code
in current generation cochlear

implant users.

And so the goal,
remember, is to allow

the users to understand speech.

It's not in terms of
recognizing musical intervals.

Now, if cochlear implant
companies were based in China,

maybe the goal of
understanding Mandarin Chinese,

which is total, would be
more important, but so far,

that hasn't happened.

AUDIENCE: Are you
more comfortable

with speaking with people
or are you more comfortable

with not speaking with people?

SHEILA: Well, I'm
more comfortable using

sign language, but I don't mind
going up in front of people

and speaking.

PROFESSOR: So one time,
I had a demonstrator

get asked this question.

What's the stupidest
thing you've ever

done with your cochlear implant?

And he had a
response right away.

He said when I first got my
implant, I went to the beach.

And I was 13 years old, and
I was a typical teenager.

And I saw someone else
with a cochlear implant,

and that was great
because it was

the first person
I had ever seen.

And so I said, let's
swap processors.

And that was actually
a very stupid thing

to do because each cochlear
implant user is not

only programmed for their
coding for frequency,

but they're coding for how much
shock goes into auditory nerve.

And some people
who have electrodes

close to the auditory nerve
don't need much current all,

but if your electrode is far
away you need a lot of current.

And this fellow got
a processor that

had been dialed in
a lot of current,

and so he got a big
severe shock when

you turn the other person's
cochlear implant on.

So that's something they
tell you not to do, right?

SHEILA: I don't think
anybody told me that.

But clearly I was like,
OK, total wipe out.

That's a bad shock.

PROFESSOR: You did that also?

SHEILA: Well, we both did.

We exchange at the same time.

PROFESSOR: Kids don't usually
listen to adults, right?

So are there a lot
of students at MIT

who use a cochlear implant?

SHEILA: So far, by now,
I think I'm the only one.

But last year, there were
two of us, but he graduated.

So this year, I'm the only one.

But I'm not the
only deaf student.

There are like two or
three other deaf student,

but they wear hearing aids.

PROFESSOR: Question.

AUDIENCE: How often
do you turn it off--

or how often is it off?

SHEILA: Oh, I turn
it off every night.

[INAUDIBLE] I go to
bed because there's

no point when I go
to sleep, right?

And when I take a
shower or go swimming

or if I want to have
a [INAUDIBLE] day.

On campus sometimes,
I would get so tired

of listening to people,
I would just take it off.

PROFESSOR: Which classes
do you turn it on

and which classes
do you turn it off?

That's OK.

How long does your battery last?

SHEILA: My battery last like 3
or 4 days, disposable battery,

3 or 4 days, but rechargeable
battery it's like one day.

PROFESSOR: And do
you have an implant

on one side only, or both sides?

SHEILA: In my right
ear, it's just one side.

PROFESSOR: Are you going
to get it in the other ear?

SHEILA: I'm not so sure
because it takes time.

I had to go through a surgery,
to see doctors, and so

on, so I'm not sure at that
time because I'm so busy at MIT.

AUDIENCE: What kind of alarm
clock helps you to wake up?

PROFESSOR: Do you
have an alarm clock?

SHEILA: Oh, yes.

I have a special alarm clock.

So I know you guys
use a typical alarm.

They make loud noises.

But for me, I use alarm
clock and a flashing lamp,

so it just flash light on
me that helps to wake me up.

But some other people say
it doesn't work for them,

so what they do, they take
a small vibrator thing

and tuck it under their
pillow or mattress,

so it's like that then
shocks them awake.

PROFESSOR: What other
kinds of problems

do you have with your
implant besides noise?

SHEILA: I wish it was really
waterproof because if I

go swimming with my buddies
who are not deaf, then

how can I hear them.

But right now, it's
like a computer,

so obviously, I can't
just jump into water.

AUDIENCE: I was going to ask
who taught you sign language.

SHEILA: Do you know
some sign language?

AUDIENCE: A little, but
where did you learn?

SHEILA: [INAUDIBLE] I learned
when I was here at MIT.

That was about
like two years ago,

so I took a class at Harvard.

And then from there, I
met a lot of deaf people

here at MIT and
outside of MIT, so I

was able to be comfortable
in sign language.

I don't know.

I guess it's not
really hard for me

to learn sign
language compared to,

let's say Spanish, because
it's more official.

You don't need to
listen or speak,

so it's really like all
hands and [INAUDIBLE].

So it was pretty natural
for me to pick it up.

And I use sign language on a
daily basis with my boyfriend

or with my friends or whenever
I ASL interpreter for my class.

PROFESSOR: So you often
have an ASL interpreter?

SHEILA: Yeah, not all, but
it depends on the class.

For example, if the class is
math or science lecture based,

like one hour long lecture,
then I use [INAUDIBLE]

like real time
closed captioning.

Someone sit next to me,
and on the computer screen,

I read whatever professor
saying in real time,

and that person
type out everything.

Another class, like more of
a lab or a hands on class

or more moving around,
then I use ASL interpreter

because it's just awkward to
carry around a laptop reading

words on a screen.

PROFESSOR: What do you want
to do after you graduate?

SHEILA: Right now, I'm
applying to one Ph.d program

at Harvard that's a
program he is a part of,

so he may be my
professor next year even.

PROFESSOR: Yeah.

If you graduate.

What's the program?

This is a little sales pitch.

You can tell them about it.

SHEILA: The program
is part of Harvard,

but it was a part of MIT before.

But it's a Ph.d program
called Speech and Hearing

Bioscience and Technology.

Right?

PROFESSOR: Right.

SHEILA: And it's a program
that focus on hearing, cochlear

implant, hearing
aids, or anything

related to hearing and speech.

So right now, I'm
applying to that program.

We'll see how it goes.

PROFESSOR: Good.

AUDIENCE: This is personal,
but did your boyfriend already

know sign language?

SHEILA: Oh, he's deaf himself,
so he knows sign language.

But he's like me.

He could speak and sign.

But difference is
he had cochlear--

no wait-- he had hearing
aid, I have cochlear implant.

AUDIENCE: Do you think that
you've become a faster reader?

Like do you think you're faster
at reading than most people

because you rely on it more?

SHEILA: I would be more what?

Faster?

AUDIENCE: Faster at reading.

SHEILA: Faster at reading lips?

AUDIENCE: Like reading words
on a screen or reading text.

SHEILA: That's a good question.

I never thought of that.

It's a possibility because
yeah, you're right.

Have you seen it in person?

AUDIENCE: I haven't seen it.

SHEILA: You haven't seen it.

So it's like on
that comp screen,

where she type out
words really fast.

So I have to read fast.

But after one hour, I
got too tired to read,

so I just look around the room.

The good thing is after class,
she send me a transcript,

so I will go back
and look at it again.

So I mean, it's really tiring
to look at computer screen,

for one hour straight,
reading words really quickly.

PROFESSOR: OK.

So the cochlear
implant is sometimes

called the most successful
neural prosthesis,

and here we have an example.

So let's give Sheila a hand.

Thank you very much for coming.

And we'll talk next time
about brain stem reflexes.

So we'll hang around if you
have any other questions.