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

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00:00:28,010 --> 00:00:33,270
Last time, we were talking
about the auditory pathway

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in the brain, the
central auditory pathway,

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starting with the
cochlear nucleus

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and going up through
the various brain

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00:00:42,970 --> 00:00:46,690
stem, the thalamic and
cortical auditory areas.

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00:00:47,780 --> 00:00:51,070
And then we focused mainly
on the cochlear nucleus,

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00:00:51,070 --> 00:00:55,280
which is the very first of those
many auditory central nuclei.

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00:00:55,280 --> 00:00:59,220
And we talked
about the diversity

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00:00:59,220 --> 00:01:03,930
of cell types or neuron
types in the cochlear nucleus

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00:01:03,930 --> 00:01:07,230
and the diversity
of response types

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00:01:07,230 --> 00:01:11,950
when you monitor the responses
of single neurons to sound.

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00:01:13,580 --> 00:01:17,930
And we did some attempts at
correlation between the two.

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00:01:17,930 --> 00:01:20,530
And those are firmly established
in the cochlear nucleus,

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00:01:20,530 --> 00:01:23,080
much better than anywhere
else in the auditory

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00:01:23,080 --> 00:01:24,330
pathways certainly.

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00:01:24,330 --> 00:01:28,470
So any questions from last time?

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00:01:34,060 --> 00:01:40,500
So today's lecture is on
hearing loss and implants that

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00:01:40,500 --> 00:01:43,800
restore our sense of hearing
if we happen to be deaf.

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00:01:45,280 --> 00:01:47,510
And I've written
a little summary

28
00:01:47,510 --> 00:01:50,550
of what I want to cover
today on the board.

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00:01:50,550 --> 00:01:54,350
So we'll start out with the
first 2/3 of the lecture being

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00:01:54,350 --> 00:01:55,270
on hearing loss.

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00:01:56,840 --> 00:02:01,740
And we've mentioned a little
about the conductive apparatus,

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00:02:01,740 --> 00:02:07,220
the eardrum, the three
ossicles in the middle ear,

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00:02:07,220 --> 00:02:10,320
conveying the vibrations
to the inner ear.

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00:02:10,320 --> 00:02:15,100
And I think we had an example of
one type of conductive hearing

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00:02:15,100 --> 00:02:16,020
loss.

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00:02:16,020 --> 00:02:19,630
If you have, obviously, an
interruption of that ossicular

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00:02:19,630 --> 00:02:23,650
chain, then the
vibrations are going

38
00:02:23,650 --> 00:02:27,469
to be reduced in the inner
ear in the conduction pah--

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00:02:27,469 --> 00:02:29,260
because the conduction
path is interrupted.

40
00:02:30,360 --> 00:02:35,970
So those are relatively
straightforward concepts,

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00:02:35,970 --> 00:02:38,580
and so consider those covered.

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00:02:38,580 --> 00:02:41,950
Today, I want to talk
about the, perhaps,

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00:02:41,950 --> 00:02:44,820
more common types
of hearing loss

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00:02:44,820 --> 00:02:47,900
that are grouped under
the name sensorineural

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00:02:47,900 --> 00:02:54,060
because the sensory cells, or
the nerve fibers themselves,

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00:02:54,060 --> 00:02:54,570
are damaged.

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00:02:55,930 --> 00:02:59,110
And in that case, it's
not so easy to understand

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00:02:59,110 --> 00:03:01,710
how we might correct
them by putting

49
00:03:01,710 --> 00:03:06,340
in an artificial middle ear
ossicle or something like that.

50
00:03:07,510 --> 00:03:14,360
This is a bit of a misnomer
in that perhaps 99% of hearing

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loss and deafness of
this type was really

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00:03:17,610 --> 00:03:21,675
based on the sensory
cells, so the hair cells

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are the prime culprit in people
who have sensorineural hearing

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00:03:25,521 --> 00:03:26,020
loss.

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00:03:28,360 --> 00:03:30,845
The most vulnerable,
of the two types

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of hair cells we've
been talking about,

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are the outer hair cells.

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00:03:35,000 --> 00:03:39,070
Any of the various causes that
we'll talk about that damage

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our hearing affect
the outer hair

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

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and the reason for
that is not known.

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

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

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those hair cells in the
basal turn of the cochlea

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are more vulnerable than those
in more a apical regions.

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Reason for that is
not known either.

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It's a very interesting
phenomenon with no basis

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that we know about.

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We'll talk about permanent
and temporary hearing

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loss, the various
causes of hearing loss,

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

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00:04:23,580 --> 00:04:27,265
prostheses, or implants, that
are used to restore hearing.

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And the most famous
of those, of course,

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is the cochlear implant.

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

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deaf, who uses a
cochlear implant,

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

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and answer questions if
you want to ask them of her

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about her cochlear implant.

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We'll also cover a couple
other different types

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of implants that are
used to restore hearing.

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So this first slide talks about
sensorineural hearing loss

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00:05:00,520 --> 00:05:01,020
in general.

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And a very common pattern of
sensorineural hearing loss,

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which comes from the basal
turn being most affected.

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00:05:12,070 --> 00:05:14,210
This is an audiogram,
if you will,

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

88
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hearing threshold as a function
of sound frequency for,

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in this lower curve,
a normal hearing

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

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00:05:33,280 --> 00:05:38,015
who has a mild to moderate
sensorineural hearing loss.

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And so as you can
see, this individual

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00:05:42,410 --> 00:05:45,230
with the hearing loss has
perfectly normal hearing

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00:05:45,230 --> 00:05:50,070
thresholds up to the middle
frequency, 1,000 Hertz,

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00:05:50,070 --> 00:05:52,470
but then their
threshold of hearing

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00:05:52,470 --> 00:05:56,260
deviates from the normal so
that by about 10,000 Hertz,

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00:05:56,260 --> 00:05:59,570
they have a hearing
loss of 60 dB or so.

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00:05:59,570 --> 00:06:03,590
This is a very common
pattern of hearing loss that

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arises because, for some
reason, the basal turn is

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more affected.

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The basal turn is where
you have the responses

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to the very highest
sound frequencies.

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00:06:17,630 --> 00:06:21,810
This person will come into
the Massachussetts Eye and Ear

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00:06:21,810 --> 00:06:26,740
Infirmary, for example,
and complain to the doctors

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00:06:26,740 --> 00:06:30,200
and audiologists there when
the hearing loss becomes

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00:06:30,200 --> 00:06:34,160
noticeable, when they have a
problem understanding speech.

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00:06:35,710 --> 00:06:39,950
Hearing loss is
intimately entwined

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00:06:39,950 --> 00:06:43,230
with our perception and
understanding of speech.

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00:06:44,360 --> 00:06:49,090
And so when people have
problems understanding speech,

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they often seek medical advice.

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00:06:51,080 --> 00:06:56,530
Now, the most important
frequencies for those in speech

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are between about
300 and 4,000 Hertz.

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

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00:07:03,070 --> 00:07:07,210
getting into the
speech range, and they

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may have problems discerning
the more high frequency

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00:07:10,560 --> 00:07:11,540
parts of speech.

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00:07:11,540 --> 00:07:12,970
So what are those?

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00:07:12,970 --> 00:07:18,800
So typically vowels, which
have the formants that we talk

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about, have very low
frequency, so something

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00:07:21,940 --> 00:07:24,015
like ahhh and oooh.

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00:07:24,015 --> 00:07:25,265
They are very low frequencies.

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00:07:27,190 --> 00:07:29,850
But I think if you could read
this diagram a little better,

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00:07:29,850 --> 00:07:33,020
you'd understand that
high-pitched sounds

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00:07:33,020 --> 00:07:37,690
like the "sss" sound
of an s, or something

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00:07:37,690 --> 00:07:40,950
that has an abrupt
onset, like a "t",

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has a lot of high
frequencies in that sound.

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00:07:44,470 --> 00:07:49,510
And so those are going to be
the first types of speech sounds

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that are hard to
understand for the person

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00:07:51,620 --> 00:07:56,870
with the impaired graph
on the top slide there.

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00:07:58,330 --> 00:08:01,220
Now at first, you
might say, well,

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what we should do is get a
hearing aid that amplifies

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00:08:05,610 --> 00:08:10,810
the frequencies that
are in loss area OK.

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So to do that,
you'd have to have

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a pretty sophisticated
hearing aid.

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00:08:15,190 --> 00:08:18,490
You'd have to, for
each sound frequency,

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dial in the exact
amount of amplification.

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00:08:21,680 --> 00:08:25,450
And hearing aids are
very good these days,

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00:08:25,450 --> 00:08:30,260
and there are hearing aids
that can be used on a frequency

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00:08:30,260 --> 00:08:33,179
specific manner, that is
don't amplify anything

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00:08:33,179 --> 00:08:37,277
at low frequencies and amplify
exactly the amount of loss

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00:08:37,277 --> 00:08:38,110
at high frequencies.

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00:08:39,250 --> 00:08:41,750
So at first, it sounds
like a good idea,

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00:08:41,750 --> 00:08:46,040
but we'll get into the reason
that that doesn't always

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00:08:46,040 --> 00:08:49,480
work later on.

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00:08:49,480 --> 00:08:54,460
So that simple solution,
just install a hearing aid--

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

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people-- is simply an amplifier.

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00:09:02,560 --> 00:09:03,775
It has a microphone.

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It picks up sound.

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It boosts the sound
in whatever frequency

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ranges the audiologist programs.

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00:09:12,850 --> 00:09:17,710
And then it has a little
speaker and it speaks or plays

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the boosted sound into the
ear canal of the person.

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00:09:20,847 --> 00:09:21,930
So it's just an amplifier.

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So you can have hearing
aids that work very well

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00:09:29,140 --> 00:09:31,360
and their frequency tailored.

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And they especially
work very well

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for the type of
hearing loss that's

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called the conductive
hearing loss because, simply,

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the problem is getting the
sound into the inner ear,

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and amplifying the
sound, in a person

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with a conductive hearing
loss, works very well.

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00:09:49,580 --> 00:09:52,520
It doesn't work so well
in sensorineural hearing

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00:09:52,520 --> 00:09:54,940
loss for reasons we'll
get into in a little bit.

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Now how do these
hearing losses happen?

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

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00:10:08,870 --> 00:10:12,360
We all have fun with sounds,
and we tend to have a lot of fun

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00:10:12,360 --> 00:10:13,845
when the sounds
are very intense.

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00:10:14,990 --> 00:10:18,790
And these are so-- this is an
old transparency obviously.

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00:10:18,790 --> 00:10:23,310
But this is a graph of
sound pressure level here.

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00:10:23,310 --> 00:10:26,940
Remember the thresholds of
hearing are way down here.

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And these are some
example sounds

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that have very high
level, and most of these

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00:10:32,240 --> 00:10:36,520
are damaging, at least if you
listen to them long enough.

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00:10:36,520 --> 00:10:42,250
Obviously, gunshots,
firecrackers are very damaging.

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00:10:42,250 --> 00:10:45,920
Those sounds are in
excess of 120 dB.

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00:10:45,920 --> 00:10:50,320
So a single gunshot, if
it's close to your head,

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00:10:50,320 --> 00:10:51,520
can be damaging.

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00:10:51,520 --> 00:10:56,340
So we had-- we're going
to have an example of that

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00:10:56,340 --> 00:10:57,730
in just a minute.

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00:10:57,730 --> 00:11:00,380
Some of these sounds
are more moderate,

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00:11:00,380 --> 00:11:05,710
around the region of 100 dB SPL,
for example, a chainsaw, a leaf

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00:11:05,710 --> 00:11:09,300
blower, the symphony
orchestra here.

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00:11:09,300 --> 00:11:11,470
So everybody goes to
the symphony, right?

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00:11:11,470 --> 00:11:14,650
So obviously,
these things depend

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00:11:14,650 --> 00:11:17,410
on how close you are
to the object that's

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00:11:17,410 --> 00:11:19,090
generating the sound, right?

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00:11:19,090 --> 00:11:20,600
So if you go to the
Boston Symphony,

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00:11:20,600 --> 00:11:22,350
you're not going to
endure a hearing loss.

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00:11:22,350 --> 00:11:25,360
But if you have good
seats and are looking down

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00:11:25,360 --> 00:11:28,430
on the symphony, you'll see
that a lot of the woodwind

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00:11:28,430 --> 00:11:31,190
players who are sitting
right in front of the brass,

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00:11:31,190 --> 00:11:33,570
for example, the
trumpet players, they

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00:11:33,570 --> 00:11:35,620
have a little
screen behind them,

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00:11:35,620 --> 00:11:38,360
a plexiglass screen that's
pretty invisible unless you're

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00:11:38,360 --> 00:11:39,590
looking for it.

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00:11:39,590 --> 00:11:43,980
That causes a sound shadow,
and so it protects their ears

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00:11:43,980 --> 00:11:45,480
from the blast of the bras.

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00:11:46,720 --> 00:11:48,212
And I've also been
in the symphony

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00:11:48,212 --> 00:11:50,420
where, sometimes, the woodwind
players would actually

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00:11:50,420 --> 00:11:53,450
put in ear plugs when
there's a big brass solo,

202
00:11:53,450 --> 00:11:56,229
and brass is blowing like crazy.

203
00:11:56,229 --> 00:11:58,270
And then after that big
solo, they take them out,

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00:11:58,270 --> 00:12:00,300
and they play their
own little solo.

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00:12:01,430 --> 00:12:03,550
So professional
musicians are obviously

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00:12:03,550 --> 00:12:05,220
very worried about
their hearing.

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00:12:05,220 --> 00:12:09,730
And it can be, if you're
close to a trumpet or a brass

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00:12:09,730 --> 00:12:13,600
instrument, deafening-- or
in front of a big timpani

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00:12:13,600 --> 00:12:18,570
or snare drums-- of
course, these things

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00:12:18,570 --> 00:12:21,910
depend on how long
you listen to them,

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00:12:21,910 --> 00:12:23,690
so the damage is cumulative.

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00:12:23,690 --> 00:12:27,440
It may take many years
of exposure at 90 dB

213
00:12:27,440 --> 00:12:30,640
to produce a hearing
loss even though exposure

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00:12:30,640 --> 00:12:33,610
to a really high sound
level, like the 160 dB,

215
00:12:33,610 --> 00:12:38,290
may give you hearing loss
after just a single exposure.

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00:12:38,290 --> 00:12:40,000
So legally, employers
are supposed

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00:12:40,000 --> 00:12:42,230
to provide hearing
protection for their workers

218
00:12:42,230 --> 00:12:47,760
if you send a worker
in to an 85 dB

219
00:12:47,760 --> 00:12:50,140
sound pressure level
environment, like is

220
00:12:50,140 --> 00:12:52,630
common in a factory,
you are supposed

221
00:12:52,630 --> 00:12:55,070
to provide the workers
with hearing protection

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00:12:55,070 --> 00:12:57,000
if it's an 8 hour shift.

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00:12:57,000 --> 00:12:59,270
If it's only a 4 hour
shift, you don't have to.

224
00:13:01,000 --> 00:13:05,740
If the sound level is 95 dB,
it's something like 2 hours.

225
00:13:05,740 --> 00:13:10,650
If it's 100 dB, you can expose
someone to an hour of that

226
00:13:10,650 --> 00:13:14,590
without hearing protection,
but if it's longer than that,

227
00:13:14,590 --> 00:13:16,220
you have to provide
hearing protection.

228
00:13:19,450 --> 00:13:20,570
So here's some example.

229
00:13:20,570 --> 00:13:24,030
Movie theaters,
Godzilla is 118 dB

230
00:13:24,030 --> 00:13:25,685
because it's a terrible roar.

231
00:13:26,910 --> 00:13:29,960
It can be deafening if you are
right near the loudspeaker.

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00:13:29,960 --> 00:13:31,901
And if you go to
Godzilla 100 times.

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00:13:31,901 --> 00:13:32,400
OK?

234
00:13:34,750 --> 00:13:35,830
All right.

235
00:13:35,830 --> 00:13:41,340
So loud sound is one of
the causes of hearing loss,

236
00:13:41,340 --> 00:13:43,130
so let's just make
a little list here.

237
00:13:58,210 --> 00:14:00,310
High level sound
is certainly one

238
00:14:00,310 --> 00:14:02,040
of the causes of
hearing loss, and I

239
00:14:02,040 --> 00:14:05,780
think we have some
examples here.

240
00:14:05,780 --> 00:14:11,830
So this is an example
from some research that

241
00:14:11,830 --> 00:14:14,690
was done by one of
the professors I had

242
00:14:14,690 --> 00:14:17,340
in graduate school, Joe Hawkins.

243
00:14:17,340 --> 00:14:21,790
And he studied
temporal bones where

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00:14:21,790 --> 00:14:24,250
the cochlear is in humans.

245
00:14:24,250 --> 00:14:28,190
So he would get temporal bones
after a subject had passed away

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00:14:28,190 --> 00:14:30,670
and had donated their
body to science.

247
00:14:30,670 --> 00:14:34,940
And they were useful if he knew
something about the individual,

248
00:14:34,940 --> 00:14:37,460
like if they had
their hearing tested

249
00:14:37,460 --> 00:14:39,741
or if you knew a little
bit about what activities

250
00:14:39,741 --> 00:14:40,240
they liked.

251
00:14:42,580 --> 00:14:44,690
These particular
data are from a human

252
00:14:44,690 --> 00:14:48,260
who is an active hunter,
fired a gun a lot.

253
00:14:51,270 --> 00:14:56,070
And the specimens shown
in the photomicrographs

254
00:14:56,070 --> 00:14:59,170
here are looking
down onto the surface

255
00:14:59,170 --> 00:15:04,670
of the inner ear, or
cochlea, on the left side

256
00:15:04,670 --> 00:15:06,256
and the right side
of the subject.

257
00:15:08,030 --> 00:15:11,860
The bone that's on the
snail shell, or cochlea,

258
00:15:11,860 --> 00:15:14,650
has been thinned away
with a dental drill,

259
00:15:14,650 --> 00:15:18,740
and you can see very
nicely the basal turn.

260
00:15:18,740 --> 00:15:21,310
The apical turn, you can't
really see very well from that,

261
00:15:21,310 --> 00:15:24,280
but you can thin the
apical turn as well.

262
00:15:24,280 --> 00:15:24,780
Sometimes.

263
00:15:24,780 --> 00:15:27,150
It's cut off and thinned
in a different dish.

264
00:15:28,600 --> 00:15:30,620
But anyway, what you're
looking at here--

265
00:15:30,620 --> 00:15:33,395
I should get out my pointer,
so I point a little better.

266
00:15:40,950 --> 00:15:45,990
So this is the very basal end
of the cochlea and spiraling up.

267
00:15:45,990 --> 00:15:49,730
And the human has about 2
and 1/2 or 3 complete turns

268
00:15:49,730 --> 00:15:50,355
of the cochlea.

269
00:15:51,610 --> 00:15:55,600
And this white structure
here is the organ

270
00:15:55,600 --> 00:15:57,725
of Corti sitting on
the basilar membrane.

271
00:16:00,740 --> 00:16:04,790
This specimen is stained with
a stain called osmium, which

272
00:16:04,790 --> 00:16:09,630
stains lipids and especially
myelinated nerve fibers,

273
00:16:09,630 --> 00:16:12,900
so you can see a lot of
myelinated nerve fibers.

274
00:16:12,900 --> 00:16:15,690
They looks like
threads coming out.

275
00:16:15,690 --> 00:16:17,375
And here's some more
threads up here.

276
00:16:18,460 --> 00:16:22,100
And I said the organ
of Corti is here,

277
00:16:22,100 --> 00:16:26,200
but actually, it's completely
gone here on the left side,

278
00:16:26,200 --> 00:16:29,190
and you can see it
begin right about here

279
00:16:29,190 --> 00:16:32,660
and go apically here up
into the apical turn.

280
00:16:32,660 --> 00:16:34,470
You can see a very
little bit of it

281
00:16:34,470 --> 00:16:38,340
in the extreme basal
part of the cochlea,

282
00:16:38,340 --> 00:16:40,720
and that's diagrammed
here on this graph.

283
00:16:40,720 --> 00:16:44,930
This is the length along
the basilar membrane

284
00:16:44,930 --> 00:16:48,470
from the base over here
on the right to the apex.

285
00:16:49,560 --> 00:16:53,084
And this y-axis graphs the
percent of the hair cells

286
00:16:53,084 --> 00:16:53,875
that are remaining.

287
00:16:54,950 --> 00:16:57,820
And in the basal
turn, they're almost

288
00:16:57,820 --> 00:16:59,930
zero hair cells remaining.

289
00:16:59,930 --> 00:17:01,450
They're all gone.

290
00:17:01,450 --> 00:17:04,770
Maybe a couple little
islands here and there,

291
00:17:04,770 --> 00:17:08,089
but it's virtually
100% hair cell loss.

292
00:17:08,089 --> 00:17:11,619
And as you go around
the upper basal turn,

293
00:17:11,619 --> 00:17:13,819
you have most of the
hair cells remaining

294
00:17:13,819 --> 00:17:16,904
in the case of the solid line,
which refers to the inner hair

295
00:17:16,904 --> 00:17:17,404
cells.

296
00:17:18,579 --> 00:17:21,300
And then you have, in the
dashed lines, the three

297
00:17:21,300 --> 00:17:24,869
rows of outer hair
cells, and there, maybe

298
00:17:24,869 --> 00:17:28,760
between 30% and 70%
remaining depending

299
00:17:28,760 --> 00:17:29,860
exactly where you are.

300
00:17:29,860 --> 00:17:33,230
But here again, something
has damaged these hair cells,

301
00:17:33,230 --> 00:17:36,650
completely wiped them out in
the basal half of the cochlea.

302
00:17:36,650 --> 00:17:38,760
And wiped a lot of
the outer hair cells

303
00:17:38,760 --> 00:17:42,250
out and not very many of the
inner hair cells are wiped out.

304
00:17:43,890 --> 00:17:46,794
Here's the subject's
right cochlea.

305
00:17:46,794 --> 00:17:48,710
And in this case, you
can see-- you don't even

306
00:17:48,710 --> 00:17:51,670
need the graph-- you can
see that the organ of Corti

307
00:17:51,670 --> 00:17:54,470
is pretty intact.

308
00:17:54,470 --> 00:17:57,790
Here is a little island
of loss, and then

309
00:17:57,790 --> 00:17:59,920
another little island
of loss, but then you

310
00:17:59,920 --> 00:18:03,840
have an intact organ of Corti
all the way up to the apex,

311
00:18:03,840 --> 00:18:08,030
and that's reflected in the
counts here where you have,

312
00:18:08,030 --> 00:18:11,460
except at the very basal
part of the cochlea which

313
00:18:11,460 --> 00:18:13,460
doesn't appear in
the micrograph,

314
00:18:13,460 --> 00:18:16,400
you have a pretty normal
complement of inner hair cells.

315
00:18:17,697 --> 00:18:19,530
Outer hair cells are
not in such good shape,

316
00:18:19,530 --> 00:18:23,280
but they're present throughout
the cochlea in this right side.

317
00:18:24,290 --> 00:18:28,470
Now, also on here are
graphs of the nerve fibers.

318
00:18:29,720 --> 00:18:33,380
Those are these little
thread-like stained elements

319
00:18:33,380 --> 00:18:36,600
here that appear very
nicely in this osmium stain,

320
00:18:36,600 --> 00:18:41,500
and they're pretty much
intact through the cochlea.

321
00:18:41,500 --> 00:18:45,040
Maybe in places here where the
hair cell loss is really bad,

322
00:18:45,040 --> 00:18:46,700
some of the nerve
fibers are gone,

323
00:18:46,700 --> 00:18:49,270
and that's indicated by
this interruption here.

324
00:18:49,270 --> 00:18:51,470
But this is another
example where

325
00:18:51,470 --> 00:18:56,890
you can have whatever damaged
this fellow's hair cells, left

326
00:18:56,890 --> 00:18:59,550
the nerve fibers
relatively intact.

327
00:18:59,550 --> 00:19:01,630
And this offers some
hope to somebody

328
00:19:01,630 --> 00:19:05,430
who wants to install a
prosthesis like the cochlear

329
00:19:05,430 --> 00:19:09,029
implant and stimulate the
remaining nerve fiber just

330
00:19:09,029 --> 00:19:10,570
because they're
going to stick around

331
00:19:10,570 --> 00:19:12,740
even if a lot of the
hair cells are gone.

332
00:19:14,100 --> 00:19:18,730
So this subject, as I said,
was an enthusiastic hunter,

333
00:19:18,730 --> 00:19:20,310
and a he was right-handed.

334
00:19:21,540 --> 00:19:24,010
And as you can see
right here, this

335
00:19:24,010 --> 00:19:26,480
is a top view of a
person firing a rifle.

336
00:19:27,820 --> 00:19:30,500
The left ear of the
subject is pointed

337
00:19:30,500 --> 00:19:32,300
toward the tip of
the gun, and that's

338
00:19:32,300 --> 00:19:33,820
where the bullet
emerges, and that's

339
00:19:33,820 --> 00:19:37,790
where the shock wave of
the rifle, when it fires,

340
00:19:37,790 --> 00:19:38,500
comes out.

341
00:19:38,500 --> 00:19:42,820
This is a modern rifle,
not a flintlock rifle

342
00:19:42,820 --> 00:19:45,580
where you have a lot of smoke
and sound coming out down here.

343
00:19:45,580 --> 00:19:48,090
Most of the sound comes
at the tip of the gun.

344
00:19:48,090 --> 00:19:51,340
And this subject's left ear
is pointed right to that

345
00:19:51,340 --> 00:19:53,640
and has taken the
brunt of the blast

346
00:19:53,640 --> 00:19:56,240
in terms of the
loss of hair cells.

347
00:19:56,240 --> 00:20:00,010
The right ear of the
subject is pointed more away

348
00:20:00,010 --> 00:20:01,950
from the tip of the
gun and is protected

349
00:20:01,950 --> 00:20:05,560
and has a pretty normal
complement of hair cells.

350
00:20:05,560 --> 00:20:08,370
Now, that's not saying
that this person didn't

351
00:20:08,370 --> 00:20:11,560
go to lots of rock
concerts, and didn't

352
00:20:11,560 --> 00:20:14,050
take lots of drugs that
damage your hearing,

353
00:20:14,050 --> 00:20:17,840
and isn't an 80-year-old
person, so we're

354
00:20:17,840 --> 00:20:20,230
going to add a few
things to our list here.

355
00:20:24,780 --> 00:20:33,020
There are some drugs, for
example aminoglycoside

356
00:20:33,020 --> 00:20:42,010
antibiotics-- they are
really great antibiotics,

357
00:20:42,010 --> 00:20:45,800
but they have this side effect
of damaging the hair cells.

358
00:20:47,610 --> 00:20:55,570
Three, the aging
process damages hearing.

359
00:20:55,570 --> 00:21:01,300
And in this kind of a study
where you're using a human,

360
00:21:01,300 --> 00:21:05,470
you cannot control for these
other factors and others that I

361
00:21:05,470 --> 00:21:11,230
haven't, but what you can do
then is compare left to right.

362
00:21:11,230 --> 00:21:14,730
Because presumably,
a subject took drugs,

363
00:21:14,730 --> 00:21:17,565
and they appeared in both the
left and right in your ears.

364
00:21:18,750 --> 00:21:23,010
And obviously, the
subject had the same aging

365
00:21:23,010 --> 00:21:26,500
in the left and right side,
so whatever differences there

366
00:21:26,500 --> 00:21:28,860
are between the
left and the right,

367
00:21:28,860 --> 00:21:31,950
we attribute then to
the blast from the rifle

368
00:21:31,950 --> 00:21:33,360
that the subject shot.

369
00:21:33,360 --> 00:21:36,740
So this cause of
left right difference

370
00:21:36,740 --> 00:21:38,890
would be attributed to
the high level sound.

371
00:21:45,210 --> 00:21:50,240
Here are some pictures
from an experiment animal

372
00:21:50,240 --> 00:21:54,690
that has undergone a high sound
level, or an overexposure.

373
00:21:56,020 --> 00:21:59,220
This is a normal-- I
think, in this case,

374
00:21:59,220 --> 00:22:01,720
it's a Guinea pig cochlea.

375
00:22:01,720 --> 00:22:06,220
And you see the row of
inner hair cells here.

376
00:22:06,220 --> 00:22:11,310
There is 1, 2, 3, 4, 5, about
a dozen inner hair cells.

377
00:22:11,310 --> 00:22:13,410
That's just one row
of inner hair cells.

378
00:22:13,410 --> 00:22:16,050
And then there are three rows
of outer hair cells looking down

379
00:22:16,050 --> 00:22:17,591
onto the tops of
the hair cells where

380
00:22:17,591 --> 00:22:19,670
you have the stereocilia
sticking up at you.

381
00:22:21,440 --> 00:22:24,340
And there are 12 or
15 outer hair cells

382
00:22:24,340 --> 00:22:26,790
in each of rows 1, 2, and 3.

383
00:22:26,790 --> 00:22:31,430
And it's such a regular pattern,
and they're all perfectly

384
00:22:31,430 --> 00:22:32,410
there.

385
00:22:32,410 --> 00:22:37,130
After listening to the
overexposure of sound,

386
00:22:37,130 --> 00:22:39,425
there are quite a few
inner hair cells lost.

387
00:22:40,940 --> 00:22:42,420
Those that are
remaining sometimes

388
00:22:42,420 --> 00:22:44,460
have abnormal stereocilia.

389
00:22:46,000 --> 00:22:48,480
There are number of outer
hair cells, in this case,

390
00:22:48,480 --> 00:22:50,400
in row one lost.

391
00:22:50,400 --> 00:22:53,400
And some that are remaining
are indicated by these arrows

392
00:22:53,400 --> 00:22:55,055
to have abnormal stereocilia.

393
00:22:56,660 --> 00:22:59,490
And here's another example
from a different place

394
00:22:59,490 --> 00:23:03,400
in the cochlea where almost the
entire third row of outer hair

395
00:23:03,400 --> 00:23:08,390
cells is wiped out by the
overexposure to noise.

396
00:23:10,080 --> 00:23:14,620
So what happens when
you lose a hair cell?

397
00:23:14,620 --> 00:23:19,920
Well, the nearby supporting
cells go fill in its space,

398
00:23:19,920 --> 00:23:22,130
and they take over.

399
00:23:22,130 --> 00:23:25,400
In mammals, such
damage is permanent.

400
00:23:25,400 --> 00:23:27,825
Once the hair cell is
killed, it never grows back.

401
00:23:29,220 --> 00:23:32,500
And there's a lot of
interest in trying

402
00:23:32,500 --> 00:23:36,110
to coax the nearby
supporting cells

403
00:23:36,110 --> 00:23:39,430
to, in these damage
cochleas, become hair cells.

404
00:23:41,280 --> 00:23:44,190
But so far that has
not been possible.

405
00:23:44,190 --> 00:23:47,400
The field was really
excited about 20 years ago

406
00:23:47,400 --> 00:23:51,990
when this type of damage
in a bird cochlea,

407
00:23:51,990 --> 00:23:55,780
if left for a month
or so, you see

408
00:23:55,780 --> 00:23:58,300
reemerging small hair cells.

409
00:23:58,300 --> 00:24:01,350
And if you wait long enough,
they become full hair cells.

410
00:24:01,350 --> 00:24:06,160
In the bird cochlea, the
surrounding supporting cells,

411
00:24:06,160 --> 00:24:11,770
after damage to the hair cells,
can then divide and become

412
00:24:11,770 --> 00:24:15,110
new hair cells, in the
chicken cochlea, for example.

413
00:24:15,110 --> 00:24:18,470
And this was a
serendipitous discovery

414
00:24:18,470 --> 00:24:23,545
where people were working on
damaging chicken hair cells,

415
00:24:23,545 --> 00:24:27,140
and they were always waiting a
couple days after the exposure

416
00:24:27,140 --> 00:24:29,450
to look at the cochleas.

417
00:24:29,450 --> 00:24:33,760
And there was a holiday vacation
where they exposed the animals

418
00:24:33,760 --> 00:24:36,272
before, and they
went out of town

419
00:24:36,272 --> 00:24:37,980
and came back three
weeks later, and they

420
00:24:37,980 --> 00:24:41,340
found something must have
gone wrong with the exposure

421
00:24:41,340 --> 00:24:42,890
because the hair cells are here.

422
00:24:42,890 --> 00:24:44,010
They're fine.

423
00:24:44,010 --> 00:24:45,940
But they figured out
later that, actually,

424
00:24:45,940 --> 00:24:48,075
the supporting cells
nearby had grown back.

425
00:24:49,600 --> 00:24:53,580
So that doesn't seem to help
us in the mammalian pathway.

426
00:24:53,580 --> 00:24:56,690
There's some sort of
growth factor or growth

427
00:24:56,690 --> 00:25:00,590
pathway in birds where
these hair cells grow back,

428
00:25:00,590 --> 00:25:02,300
but not in the
mammal unfortunately.

429
00:25:08,440 --> 00:25:13,150
So this is an example
from a cochlea that's

430
00:25:13,150 --> 00:25:18,970
been treated by
an aminoglycoside,

431
00:25:18,970 --> 00:25:22,330
and this is just to
remind me to tell you

432
00:25:22,330 --> 00:25:29,090
that, once again, you can count
hair cells along the cochlea.

433
00:25:29,090 --> 00:25:31,800
This is a plot of
hair cells present

434
00:25:31,800 --> 00:25:34,350
where lots of black bars
means lots of hair cells.

435
00:25:36,080 --> 00:25:40,690
And this is a beautiful
example of this particular drug

436
00:25:40,690 --> 00:25:45,220
treatment, which I
believe is kanamycin,

437
00:25:45,220 --> 00:25:48,850
and a certain dose doesn't
affect the inner hair cells

438
00:25:48,850 --> 00:25:49,350
at all.

439
00:25:50,510 --> 00:25:52,410
But look at the
outer hair cell loss

440
00:25:52,410 --> 00:25:56,640
in the basal part of the
cochlea, virtually complete

441
00:25:56,640 --> 00:26:00,000
outer hair cell loss showing
that the outer hair cells are

442
00:26:00,000 --> 00:26:04,341
more sensitive, they're more
labile to this drug treatment

443
00:26:04,341 --> 00:26:05,590
than are the inner hair cells.

444
00:26:06,650 --> 00:26:12,220
And once again, the most
vulnerable part of the cochlea

445
00:26:12,220 --> 00:26:13,760
is not the apex.

446
00:26:13,760 --> 00:26:17,080
0% distance from
the apex is up here.

447
00:26:17,080 --> 00:26:18,870
And the basal region
would be down here,

448
00:26:18,870 --> 00:26:20,990
and that's again the
most vulnerable part

449
00:26:20,990 --> 00:26:22,380
of the cochlear for some reason.

450
00:26:25,060 --> 00:26:27,770
We can speculate
about why this might

451
00:26:27,770 --> 00:26:29,950
be the case for drug treatment.

452
00:26:29,950 --> 00:26:32,970
We don't know this,
but maybe the drug

453
00:26:32,970 --> 00:26:36,035
appears in more in a
higher concentration

454
00:26:36,035 --> 00:26:37,410
in the basal part
of the cochlea.

455
00:26:38,510 --> 00:26:41,900
In the cochlea, like
you have in the brain,

456
00:26:41,900 --> 00:26:44,440
you have a blood-brain barrier.

457
00:26:44,440 --> 00:26:47,410
You have a
blood-cochlea barrier.

458
00:26:47,410 --> 00:26:50,610
Obviously, some drug has
gotten into the cochlea,

459
00:26:50,610 --> 00:26:53,970
but maybe the
blood-cochlea barrier

460
00:26:53,970 --> 00:26:56,580
is more permeable
down here in the base.

461
00:26:56,580 --> 00:26:59,080
And in the apex not
as much drug got in.

462
00:26:59,080 --> 00:27:00,760
That's an idea.

463
00:27:00,760 --> 00:27:03,680
It hasn't been borne out
by experimental evidence,

464
00:27:03,680 --> 00:27:06,620
but it's an idea that
people have in mind.

465
00:27:06,620 --> 00:27:08,430
Or, it could be
that the outer hair

466
00:27:08,430 --> 00:27:11,765
cells are just, for some reason,
easier to kill in the base.

467
00:27:12,880 --> 00:27:17,050
That's more suggestive
that all of these things

468
00:27:17,050 --> 00:27:19,760
affect the hair cells in
the base more than the apex.

469
00:27:21,010 --> 00:27:26,560
Now, these were some of the
original experiments that

470
00:27:26,560 --> 00:27:30,500
showed what outer hair cells did
for us in the sense of hearing.

471
00:27:30,500 --> 00:27:33,940
So earlier in this
course, we had the effect

472
00:27:33,940 --> 00:27:37,360
of knocking out the
outer hair cells

473
00:27:37,360 --> 00:27:39,495
by knocking out the
gene for Prestin.

474
00:27:41,350 --> 00:27:41,910
OK?

475
00:27:41,910 --> 00:27:44,040
In this case, the
outer hair cells

476
00:27:44,040 --> 00:27:46,440
are knocked out by
the drug treatment.

477
00:27:46,440 --> 00:27:49,120
So you've lesioned
the outer hair cells

478
00:27:49,120 --> 00:27:50,820
in the very basal
part of the cochlea.

479
00:27:51,710 --> 00:27:53,085
The inner hair
cells are present.

480
00:27:54,830 --> 00:27:59,130
Let's look at the tuning
curves from auditory nerve

481
00:27:59,130 --> 00:28:00,700
fibers in that preparation.

482
00:28:00,700 --> 00:28:05,350
Now let me remind you again
what's happening here.

483
00:28:05,350 --> 00:28:10,260
So you have the
inner hair cells,

484
00:28:10,260 --> 00:28:16,950
and you have the
outer hair cells,

485
00:28:16,950 --> 00:28:21,200
which have been killed
by the drug treatment.

486
00:28:21,200 --> 00:28:26,720
And then you have most of the
auditory nerve fibers coming

487
00:28:26,720 --> 00:28:32,550
from the inner hair cells
in the auditory nerve going

488
00:28:32,550 --> 00:28:33,860
to the brain.

489
00:28:33,860 --> 00:28:37,800
And the experiment then is to
if you're recording electrodes,

490
00:28:37,800 --> 00:28:41,300
record from the
auditory nerve fibers,

491
00:28:41,300 --> 00:28:46,510
get a single nerve fiber,
and take its tuning curve.

492
00:28:46,510 --> 00:28:50,640
And that's what's shown
on this top graph.

493
00:28:50,640 --> 00:28:54,950
So tuning curves from the
normal region of the cochlea

494
00:28:54,950 --> 00:28:56,500
are normal shaped.

495
00:28:56,500 --> 00:29:00,266
They have sharp tips and
tails, normal sensitivity.

496
00:29:02,197 --> 00:29:04,530
In the region of the cochlea
when the drug treatment has

497
00:29:04,530 --> 00:29:07,870
lesioned the outer hair
cells, the tuning curves

498
00:29:07,870 --> 00:29:09,650
look extremely abnormal.

499
00:29:09,650 --> 00:29:14,720
There's a tail, whatever tip
there is is a tiny little tip,

500
00:29:14,720 --> 00:29:19,560
and there's a tremendous loss
of sensitivity, as much as 60

501
00:29:19,560 --> 00:29:21,950
or more dB lost.

502
00:29:21,950 --> 00:29:24,540
Basically, these are
tipless tuning curves.

503
00:29:26,030 --> 00:29:28,750
And now we know that
the outer hair cells

504
00:29:28,750 --> 00:29:31,090
have their
electromotility function.

505
00:29:31,090 --> 00:29:33,300
They are the cochlea amplifier.

506
00:29:33,300 --> 00:29:35,930
Without the amplifier, you lose
the tip on the tuning curve.

507
00:29:37,410 --> 00:29:38,940
So that should be a mini review.

508
00:29:39,980 --> 00:29:42,630
This is the way the outer
hair cells originally

509
00:29:42,630 --> 00:29:45,702
thought-- or discovered
to be important

510
00:29:45,702 --> 00:29:47,160
in the sense of
hearing, to provide

511
00:29:47,160 --> 00:29:50,050
the normal sensitivity
and a sharp tuning.

512
00:29:50,050 --> 00:29:53,770
You can get all kinds of tuning
curve abnormalities depending

513
00:29:53,770 --> 00:29:58,160
on whether you, in this case,
lose all the outer hair cells.

514
00:29:58,160 --> 00:30:00,270
You cause disarray
of the stereocilia.

515
00:30:01,750 --> 00:30:04,820
You have partial loss
of the outer hair cells.

516
00:30:04,820 --> 00:30:09,650
All these kinds of things can
be found after noise damage

517
00:30:09,650 --> 00:30:14,130
depending on the place of
the cochlea you look at,

518
00:30:14,130 --> 00:30:18,250
the type of noise, the
length of the noise exposure,

519
00:30:18,250 --> 00:30:19,940
and the animal.

520
00:30:19,940 --> 00:30:24,820
There's a lot of variability
in noise damage from exposures

521
00:30:24,820 --> 00:30:27,020
to 10-- 10 different
animals, you

522
00:30:27,020 --> 00:30:31,260
can have 10 different types
of loss of hair cells.

523
00:30:31,260 --> 00:30:33,440
Noise damage is
tremendously variable

524
00:30:33,440 --> 00:30:34,565
from subject to subject.

525
00:30:42,400 --> 00:30:45,390
Now, we also had--
this is another review.

526
00:30:45,390 --> 00:30:49,670
We also had the example of a
psychophycial tuning curve.

527
00:30:49,670 --> 00:30:52,660
So this is a normal
psychophysical tuning curve.

528
00:30:52,660 --> 00:30:56,670
Can somebody explain to
me what the paradigm is?

529
00:30:57,940 --> 00:30:59,650
A psychophysical
tuning curve, it's

530
00:30:59,650 --> 00:31:02,037
taken from a human
listener, right?

531
00:31:02,037 --> 00:31:02,870
What's the paradigm?

532
00:31:10,490 --> 00:31:13,830
We had this in class, so we
should all know what this is.

533
00:31:13,830 --> 00:31:17,825
A psychophysical tuning
curve, you have a probe tone.

534
00:31:18,990 --> 00:31:21,030
I think that, in this
case, the probe tone

535
00:31:21,030 --> 00:31:23,060
is right at the
tip of the arrow.

536
00:31:23,060 --> 00:31:27,200
And the subject is instructed
to listen to the probe tone

537
00:31:27,200 --> 00:31:30,070
and say when you
hear the probe tone.

538
00:31:30,070 --> 00:31:31,520
Give the probe tone.

539
00:31:31,520 --> 00:31:33,270
Yes, I hear that definitely.

540
00:31:33,270 --> 00:31:33,880
Give it again.

541
00:31:33,880 --> 00:31:35,050
Oh, yes, I hear that.

542
00:31:35,050 --> 00:31:36,100
No problem.

543
00:31:36,100 --> 00:31:41,140
Then, you add a second tone,
maybe a little bit higher

544
00:31:41,140 --> 00:31:43,922
in frequency than
the probe tone.

545
00:31:43,922 --> 00:31:46,985
Probe tone was-- let's say,
in this case, 1 kilohertz.

546
00:31:48,050 --> 00:31:54,730
The second tone, masker tone
is 1.5 kilohertz, let's say.

547
00:31:54,730 --> 00:31:56,550
Introduce that.

548
00:31:56,550 --> 00:31:58,530
Person, yeah, I still
hear the probe tone.

549
00:31:58,530 --> 00:31:59,977
I hear this other tone too.

550
00:31:59,977 --> 00:32:01,310
Oh, don't pay attention to that.

551
00:32:01,310 --> 00:32:02,680
Just listen to the probe tone.

552
00:32:02,680 --> 00:32:03,870
Sure, I hear that.

553
00:32:03,870 --> 00:32:06,700
Then, you boost the level
of that second masker tone

554
00:32:06,700 --> 00:32:08,950
up to, in this case, 90 dB.

555
00:32:08,950 --> 00:32:12,089
The person says, I can't
hear that probe tone anymore.

556
00:32:12,089 --> 00:32:12,880
Can you turn it up?

557
00:32:14,040 --> 00:32:16,110
And you plot that on your graph.

558
00:32:16,110 --> 00:32:16,920
That's a hit.

559
00:32:16,920 --> 00:32:18,180
That's a point.

560
00:32:18,180 --> 00:32:22,510
In that case, the masker has
made inaudible the probe.

561
00:32:23,620 --> 00:32:26,200
And you go on varying your
frequencies and levels

562
00:32:26,200 --> 00:32:30,165
until that masker masks
the probe and the person

563
00:32:30,165 --> 00:32:31,870
says I can't hear
the probe anymore.

564
00:32:31,870 --> 00:32:35,290
And you get the so-called
psychophysical tuning curve,

565
00:32:35,290 --> 00:32:38,280
which has this
very nice tip to it

566
00:32:38,280 --> 00:32:41,650
and a long low frequency tail
from a normal hearing person.

567
00:32:43,110 --> 00:32:46,530
But a person with a
sensorineural hearing loss

568
00:32:46,530 --> 00:32:49,450
often has a psychophysical
tuning curve like this.

569
00:32:51,170 --> 00:32:53,260
This should remind you
of the tuning curves

570
00:32:53,260 --> 00:32:55,760
that we just saw from
auditory nerve fibers

571
00:32:55,760 --> 00:33:00,290
in the damaged cochlea, which
is basically a tipless tuning

572
00:33:00,290 --> 00:33:00,790
curve.

573
00:33:02,150 --> 00:33:04,620
Perhaps in this case,
the outer hair cells

574
00:33:04,620 --> 00:33:08,610
have been damaged
by fun with sounds,

575
00:33:08,610 --> 00:33:11,990
and you have just the
tail of the tuning curve.

576
00:33:13,260 --> 00:33:16,310
Now, here we come
to the crux of why,

577
00:33:16,310 --> 00:33:19,090
in this person who has
a sensorineural hearing

578
00:33:19,090 --> 00:33:22,040
loss-- they still
have hearing, but they

579
00:33:22,040 --> 00:33:26,970
have a big loss-- why won't
just a hearing aid work?

580
00:33:26,970 --> 00:33:29,330
You can certainly
install a hearing aid

581
00:33:29,330 --> 00:33:33,980
into this person's ear canal
and boost their threshold

582
00:33:33,980 --> 00:33:36,180
from what they used
to here down at 0

583
00:33:36,180 --> 00:33:39,380
dB to what they
now here at 60 dB

584
00:33:39,380 --> 00:33:41,750
You can amplify
the sound at 60 dB.

585
00:33:41,750 --> 00:33:42,940
OK, fine.

586
00:33:42,940 --> 00:33:46,020
Then, they'll start to say,
yeah, I here it no problem.

587
00:33:46,020 --> 00:33:49,770
What happens when this person
goes to a crowded restaurant,

588
00:33:49,770 --> 00:33:52,030
and there's all this
low frequency DIN?

589
00:33:53,510 --> 00:33:58,160
Well before, all the low
frequency DIN was here.

590
00:33:58,160 --> 00:34:00,560
It didn't get into
the response area

591
00:34:00,560 --> 00:34:03,880
of the sharply
tuned tuning curve.

592
00:34:03,880 --> 00:34:06,700
Now, you have all
this low frequencies

593
00:34:06,700 --> 00:34:09,790
that's amplified
by the hearing aid.

594
00:34:09,790 --> 00:34:13,880
It now gets into the response
area of the nerve fiber.

595
00:34:13,880 --> 00:34:15,980
That low frequency
signal, which you

596
00:34:15,980 --> 00:34:18,469
don't want to pay attention
to because you're listening

597
00:34:18,469 --> 00:34:23,150
at 1 kilohertz, is a
competing, or masking, stimulus

598
00:34:23,150 --> 00:34:24,929
along with the signal.

599
00:34:24,929 --> 00:34:29,120
And so now, the person with the
hearing aid and sensorineural

600
00:34:29,120 --> 00:34:31,840
hearing loss goes into
the crowded restaurant

601
00:34:31,840 --> 00:34:35,580
and says I hear very well, but
I can't understand the person

602
00:34:35,580 --> 00:34:37,830
across the table speaking to me.

603
00:34:37,830 --> 00:34:39,870
All I hear is this big noise.

604
00:34:39,870 --> 00:34:43,120
And no matter what I-- how
I adjust my hearing aid,

605
00:34:43,120 --> 00:34:44,370
it just sounds noisy.

606
00:34:44,370 --> 00:34:46,020
I can't understand anymore.

607
00:34:46,020 --> 00:34:47,000
I can hear.

608
00:34:47,000 --> 00:34:50,810
They're certainly not deaf, but
they can't understand anymore

609
00:34:50,810 --> 00:34:55,560
because before they had
sharply tuned frequency tuning,

610
00:34:55,560 --> 00:34:57,995
and now they have no
frequency tuning at all.

611
00:34:57,995 --> 00:34:59,080
It's very broad.

612
00:34:59,080 --> 00:35:02,230
That's the problem
that a hearing aid

613
00:35:02,230 --> 00:35:06,590
can't deal with in terms
of restoring normal hearing

614
00:35:06,590 --> 00:35:09,060
to a person with
sensorineural hearing loss.

615
00:35:12,850 --> 00:35:14,860
Before I start to
talk about implants,

616
00:35:14,860 --> 00:35:19,951
let me just remember to say
what other processes affect

617
00:35:19,951 --> 00:35:20,450
our hearing.

618
00:35:21,650 --> 00:35:28,290
And we have a list just so
I don't forget anything.

619
00:35:28,290 --> 00:35:38,540
And one of the important
things is genetic causes.

620
00:35:41,190 --> 00:35:43,810
So maybe you can't see that
from the back of the room,

621
00:35:43,810 --> 00:35:46,350
but number four here
is genetic causes.

622
00:35:46,350 --> 00:35:49,390
There are babies
who are born deaf,

623
00:35:49,390 --> 00:35:52,920
and in the state of
Massachusetts, in most states,

624
00:35:52,920 --> 00:35:58,630
it's mandatory to test infant
hearing at birth because you

625
00:35:58,630 --> 00:36:02,150
want to install a hearing
aid or install a cochlea

626
00:36:02,150 --> 00:36:08,120
implant at a young age if
the baby has hearing loss.

627
00:36:08,120 --> 00:36:13,810
And another cause
that we should list

628
00:36:13,810 --> 00:36:17,585
are certain kinds of infections
and disease processes.

629
00:36:20,540 --> 00:36:27,817
Number five, cause of hearing
loss is diseases, for example,

630
00:36:27,817 --> 00:36:28,316
meningitis.

631
00:36:33,530 --> 00:36:35,270
And one of the MIT
students that I

632
00:36:35,270 --> 00:36:38,760
used to use for demonstration
of cochlea implant

633
00:36:38,760 --> 00:36:44,890
is deaf because at age 12, he
got very sick with meningitis.

634
00:36:44,890 --> 00:36:50,550
And when I asked him,
how did you go deaf?

635
00:36:50,550 --> 00:36:53,010
He said, well, I got
sick with meningitis.

636
00:36:53,010 --> 00:36:59,290
And I was so sick that my MD's
treated me with aminoglycosides

637
00:36:59,290 --> 00:37:02,080
so that they would kill
the meningitis bacteria.

638
00:37:02,080 --> 00:37:06,240
And he isn't sure whether it's
the meningitis or the side

639
00:37:06,240 --> 00:37:10,070
effect of the aminoglycosides
that made him deaf.

640
00:37:10,070 --> 00:37:13,370
But when you woke up, he
was cured, but he was deaf.

641
00:37:14,600 --> 00:37:20,580
So in some cases you're not
sure which of these agents

642
00:37:20,580 --> 00:37:21,620
caused the hearing loss.

643
00:37:23,500 --> 00:37:25,590
So that's a pretty
complete list now.

644
00:37:25,590 --> 00:37:29,570
Do we have any questions about
what things cause hearing loss?

645
00:37:38,010 --> 00:37:42,050
And you might imagine
that, during our lifetime,

646
00:37:42,050 --> 00:37:47,150
some of these things will be
understood in a better way.

647
00:37:47,150 --> 00:37:50,940
It's clear why loud sound
causes hearing loss.

648
00:37:50,940 --> 00:37:52,590
I mean the mechanical action.

649
00:37:52,590 --> 00:37:54,110
These things are moving.

650
00:37:54,110 --> 00:37:57,995
You could damage the
very sensitive apparatus,

651
00:37:57,995 --> 00:37:58,870
like the stereocilia.

652
00:38:01,320 --> 00:38:04,250
Drugs, aminoglycosides
bind to some

653
00:38:04,250 --> 00:38:06,280
of the membrane
channels in hair cells.

654
00:38:07,430 --> 00:38:13,780
And maybe a therapy for this
ototoxicity, this hearing loss

655
00:38:13,780 --> 00:38:15,890
created by these
aminoglycosides,

656
00:38:15,890 --> 00:38:21,160
could be to install some
competitive binder that

657
00:38:21,160 --> 00:38:24,210
would occupy the binding
sites while you gave the drug

658
00:38:24,210 --> 00:38:24,710
therapy.

659
00:38:26,680 --> 00:38:30,750
We don't know at all what causes
the hearing loss with aging.

660
00:38:30,750 --> 00:38:35,200
That's a very active
subject in today's research.

661
00:38:35,200 --> 00:38:39,850
Genetic causes, same
way, usually these

662
00:38:39,850 --> 00:38:44,370
are some sort of developmental
factor or protein

663
00:38:44,370 --> 00:38:48,780
that's necessary for normal hair
cell development and it's lost,

664
00:38:48,780 --> 00:38:52,260
in the case of recessive
genetic problem.

665
00:38:54,080 --> 00:38:56,390
That's pretty clear
how that arises.

666
00:38:56,390 --> 00:39:01,820
Meningitis, it's not clear how
those diseases kill hair cells,

667
00:39:01,820 --> 00:39:02,810
but they certainly do.

668
00:39:04,340 --> 00:39:07,330
But there's certainly
room to imagine

669
00:39:07,330 --> 00:39:11,330
that will be worked on quite
actively in the next 10

670
00:39:11,330 --> 00:39:12,240
or 20 years.

671
00:39:12,240 --> 00:39:15,560
It's not known right
now how the hair

672
00:39:15,560 --> 00:39:17,030
cells are lost in meningitis.

673
00:39:21,000 --> 00:39:28,460
So let's talk about, now, people
who have complete hearing loss

674
00:39:28,460 --> 00:39:32,800
and are eligible for
the so-called cochlear

675
00:39:32,800 --> 00:39:35,480
implants and other types of
implants that restore hearing.

676
00:39:37,520 --> 00:39:41,790
So this is a nice
slide from, I think,

677
00:39:41,790 --> 00:39:43,920
the paper that we're
reading for today.

678
00:39:43,920 --> 00:39:46,690
And actually that reminds
me, besides that paper, which

679
00:39:46,690 --> 00:39:50,020
is a very short
one, easy to read,

680
00:39:50,020 --> 00:39:52,080
the textbook reading
that I've assigned

681
00:39:52,080 --> 00:39:54,570
for today, which
is most of chapter

682
00:39:54,570 --> 00:39:57,340
8 on auditory
prostheses is excellent.

683
00:39:57,340 --> 00:39:59,160
It's really up to date.

684
00:39:59,160 --> 00:40:02,400
It tells you a lot
about cochlear implants

685
00:40:02,400 --> 00:40:05,560
and coding for speech,
which I probably

686
00:40:05,560 --> 00:40:06,870
won't have time to get into.

687
00:40:06,870 --> 00:40:10,660
But this is a really-- I mean
hearing aids past and present,

688
00:40:10,660 --> 00:40:11,990
that's not so important.

689
00:40:11,990 --> 00:40:13,850
But it has a lot
of good information

690
00:40:13,850 --> 00:40:17,300
on cochlear implants, so
I'd encourage you definitely

691
00:40:17,300 --> 00:40:19,670
to read that textbook
passage today.

692
00:40:20,900 --> 00:40:23,650
And the research report
by Moore and Shannon

693
00:40:23,650 --> 00:40:28,030
is a very simple,
easy to read paper.

694
00:40:28,030 --> 00:40:32,050
It shows you the sites where
these various implants go.

695
00:40:32,050 --> 00:40:34,590
So the cochlear
implant, obviously,

696
00:40:34,590 --> 00:40:38,010
is installed into the
cochlea, right here.

697
00:40:39,990 --> 00:40:43,210
For people who have lost their
hearing because of a problem

698
00:40:43,210 --> 00:40:47,360
with their auditory nerve,
you put a cochlear implant in,

699
00:40:47,360 --> 00:40:49,700
and it's not going to do any
good because the messages

700
00:40:49,700 --> 00:40:52,330
aren't going to be conveyed
by the nerve into the brain.

701
00:40:53,780 --> 00:40:57,330
And so what's an example
of someone like that?

702
00:40:57,330 --> 00:41:05,620
Well, a disease process
called neurofibromatosis

703
00:41:05,620 --> 00:41:15,140
type two, or NF2, is a disease
process where the subjects get

704
00:41:15,140 --> 00:41:18,500
tumors that grow
on various nerves.

705
00:41:18,500 --> 00:41:23,250
And a very common type
of tumor in NF2 patients

706
00:41:23,250 --> 00:41:28,700
is called a
vestibular schwannoma.

707
00:41:31,710 --> 00:41:35,610
And a schwannoma is a
tumor of the schwann cells

708
00:41:35,610 --> 00:41:39,210
that normally provide the myelin
covering of peripheral nerves.

709
00:41:39,210 --> 00:41:41,290
And it grows on the
vestibular branch

710
00:41:41,290 --> 00:41:43,120
of the eighth cranial nerve.

711
00:41:43,120 --> 00:41:46,270
Obviously, that's quite
near the auditory branch

712
00:41:46,270 --> 00:41:48,110
of the eighth cranial nerve.

713
00:41:48,110 --> 00:41:49,990
And these tumors grow and grow.

714
00:41:49,990 --> 00:41:52,550
They probably rob the
nerve of the blood supply.

715
00:41:52,550 --> 00:41:54,380
They probably put
pressure on it,

716
00:41:54,380 --> 00:41:58,030
and they certainly
infiltrate the tumor cells

717
00:41:58,030 --> 00:41:59,320
in amongst the fibers.

718
00:42:00,570 --> 00:42:04,740
And when the surgeon goes in
to remove that type of tumor

719
00:42:04,740 --> 00:42:07,380
invariably the eighth
cranial nerve is cut.

720
00:42:08,490 --> 00:42:13,040
So in that case, the subject
has no nerve conveying messages

721
00:42:13,040 --> 00:42:14,640
from the cochlea into the brain.

722
00:42:15,990 --> 00:42:18,750
Well, the surgery is right here.

723
00:42:18,750 --> 00:42:20,370
You're removing a
tumor from here,

724
00:42:20,370 --> 00:42:24,550
so it's fairly easy to go
ahead and install an implant

725
00:42:24,550 --> 00:42:27,867
into the cochlear
nucleus of the brain.

726
00:42:27,867 --> 00:42:29,200
The cochlear nucleus is visible.

727
00:42:30,500 --> 00:42:34,180
And that's what's called an
auditory brainstem implant.

728
00:42:34,180 --> 00:42:36,460
It should be called a
cochlear nucleus implant,

729
00:42:36,460 --> 00:42:37,418
but it's called an ABI.

730
00:42:38,720 --> 00:42:44,160
And an ABI-- I'm not going
to talk too much about it--

731
00:42:44,160 --> 00:42:48,400
but just suffice it to say, it's
an array of surface electrodes.

732
00:42:49,580 --> 00:42:51,670
There are two
companies making these.

733
00:42:51,670 --> 00:42:56,360
One has 15, and one has 21
in a checkerboard pattern.

734
00:42:58,920 --> 00:43:03,510
And the electrodes go onto
the surface of the cochlear

735
00:43:03,510 --> 00:43:06,865
nucleus, and their placed
there during the surgery.

736
00:43:08,620 --> 00:43:12,440
There was an experimental
penetrating electrode array,

737
00:43:12,440 --> 00:43:15,310
or PABI, but that's
been discontinued

738
00:43:15,310 --> 00:43:16,385
because of side effects.

739
00:43:18,150 --> 00:43:21,800
Some of these patients
got trigeminal neuralgia,

740
00:43:21,800 --> 00:43:27,790
or pain sensations from nearby
nerves, maybe by the fact

741
00:43:27,790 --> 00:43:30,075
that these electrodes
penetrated into the brain.

742
00:43:31,350 --> 00:43:34,560
And so that underwent
an FDA trial,

743
00:43:34,560 --> 00:43:35,826
but that's no longer used.

744
00:43:37,440 --> 00:43:42,010
But this surface ABI electrode
is used in cases of NF2

745
00:43:42,010 --> 00:43:45,525
or in other cases where the
nerve function is compromised.

746
00:43:47,780 --> 00:43:50,770
Those implants don't
work very well.

747
00:43:50,770 --> 00:43:52,795
So if you look at
this graph here.

748
00:43:53,800 --> 00:43:56,500
This is a graph of the
different types of implants,

749
00:43:56,500 --> 00:43:58,830
especially I'll call your
attention to the cochlear

750
00:43:58,830 --> 00:44:03,320
implant and the auditory
brain stem implant.

751
00:44:03,320 --> 00:44:05,830
In the cochlear
implant, you've got

752
00:44:05,830 --> 00:44:12,860
a lot of people who can-- if you
do in a word recognition test,

753
00:44:12,860 --> 00:44:16,810
how often they get the
words correct, a lot of them

754
00:44:16,810 --> 00:44:19,600
are placing at
100% of the words.

755
00:44:21,490 --> 00:44:25,490
So the task here is you
stand behind the subject,

756
00:44:25,490 --> 00:44:27,620
or the audiologist stand
behind the subject,

757
00:44:27,620 --> 00:44:31,410
and they say repeat
after me, baby.

758
00:44:31,410 --> 00:44:32,745
And the person says baby.

759
00:44:35,130 --> 00:44:37,505
Sunshine, and the
person says sunshine.

760
00:44:38,806 --> 00:44:41,370
And the person says, Red Socks.

761
00:44:41,370 --> 00:44:43,950
And you say, Cardinals.

762
00:44:43,950 --> 00:44:45,730
And they got one wrong.

763
00:44:48,770 --> 00:44:51,390
But anyway, you
can do these tests

764
00:44:51,390 --> 00:44:54,090
without-- it's important
to stand behind the person

765
00:44:54,090 --> 00:44:55,660
to make sure they're
not lipreading.

766
00:44:55,660 --> 00:44:57,990
But a lot of cochlear
implant users

767
00:44:57,990 --> 00:45:01,390
can get 100% on these tests.

768
00:45:01,390 --> 00:45:04,070
Now, the ABI, auditory
brain stem implants,

769
00:45:04,070 --> 00:45:07,950
you've got many of the
subject, if not all of them,

770
00:45:07,950 --> 00:45:12,750
saying the wrong word or not
giving you any response here.

771
00:45:12,750 --> 00:45:14,870
So what good is the ABI?

772
00:45:16,800 --> 00:45:20,320
The real success story
of these prostheses

773
00:45:20,320 --> 00:45:22,940
is that the person
can understand speech.

774
00:45:22,940 --> 00:45:26,100
If the person can't
understand speech,

775
00:45:26,100 --> 00:45:29,030
this thing isn't doing
them too much good.

776
00:45:30,760 --> 00:45:34,290
So that's not to say
that the ABI isn't

777
00:45:34,290 --> 00:45:36,700
successful in certain ways.

778
00:45:36,700 --> 00:45:40,815
The ABI is sometimes thought of
as a lipreading assist device.

779
00:45:43,350 --> 00:45:46,900
So it helps these
subjects read lips better.

780
00:45:46,900 --> 00:45:49,200
For example, if
you guys are deaf

781
00:45:49,200 --> 00:45:52,530
and you look at my letters, and
I make two different sounds,

782
00:45:52,530 --> 00:45:55,050
pa and ba.

783
00:45:55,050 --> 00:45:58,740
That looks exactly the same if
you're trying to read my lips.

784
00:45:58,740 --> 00:46:00,485
But it sounds different to you.

785
00:46:00,485 --> 00:46:02,360
You guys have good
hearing, and it

786
00:46:02,360 --> 00:46:05,840
may sound a little bit
different to the ABI user,

787
00:46:05,840 --> 00:46:09,990
and it may give that ABI user
a little bit of a step up

788
00:46:09,990 --> 00:46:14,405
and help versus someone
who's just using lipreading.

789
00:46:17,590 --> 00:46:20,370
Now, just for
completeness, I'll talk

790
00:46:20,370 --> 00:46:22,305
about the auditory
midbrain implant.

791
00:46:25,340 --> 00:46:29,090
The idea here is to put
the implant higher up

792
00:46:29,090 --> 00:46:29,970
in the pathway.

793
00:46:29,970 --> 00:46:31,230
Why would you want to do that?

794
00:46:32,340 --> 00:46:34,110
Well, some people
think that the ABI

795
00:46:34,110 --> 00:46:37,000
doesn't work because there's
been this tumor here.

796
00:46:38,180 --> 00:46:41,780
And surgeon has been hacking on
the tumor to try to get it out,

797
00:46:41,780 --> 00:46:44,170
yanking and pulling on it.

798
00:46:44,170 --> 00:46:46,950
If the tumor didn't damage
the cochlear nucleus,

799
00:46:46,950 --> 00:46:49,810
well, the hacking and
tugging on it did.

800
00:46:51,060 --> 00:46:53,530
And so maybe you
should put the implant

801
00:46:53,530 --> 00:46:56,420
further up where
you haven't been

802
00:46:56,420 --> 00:46:58,120
hacking and everything's normal.

803
00:46:59,760 --> 00:47:02,864
And so that's the idea behind
the auditory midbrain implant,

804
00:47:02,864 --> 00:47:04,530
which goes into the
inferior colliculus.

805
00:47:06,010 --> 00:47:11,800
And there have
been five patients

806
00:47:11,800 --> 00:47:13,920
who've gone undergone
the auditory midbrain

807
00:47:13,920 --> 00:47:17,460
implant-- actually six,
five very well documented.

808
00:47:18,850 --> 00:47:26,100
And the outcomes have been
no better than the ABI,

809
00:47:26,100 --> 00:47:30,520
but that's because four out
of the five well-documented

810
00:47:30,520 --> 00:47:32,335
didn't hit the right spot.

811
00:47:32,335 --> 00:47:35,340
The inferior colliculus
is pretty small,

812
00:47:35,340 --> 00:47:38,720
and the part that you
really want to go into

813
00:47:38,720 --> 00:47:41,365
is the tonotopically
organized spot

814
00:47:41,365 --> 00:47:46,260
so that this needle
electrode y--

815
00:47:46,260 --> 00:47:49,760
this is a long electrode
array with about 16 contacts

816
00:47:49,760 --> 00:47:51,810
on it, in this needle.

817
00:47:51,810 --> 00:47:55,890
And that's put into the
tonotopic part of the IC,

818
00:47:55,890 --> 00:47:58,790
and it didn't get into the
right place in most people.

819
00:47:58,790 --> 00:48:02,580
But even in the one individual,
got it in the right place,

820
00:48:02,580 --> 00:48:04,185
it wasn't any
better than the ABI.

821
00:48:05,520 --> 00:48:08,590
But there is going to be another
clinical trial in which they

822
00:48:08,590 --> 00:48:10,950
implant five more subjects.

823
00:48:10,950 --> 00:48:13,880
And hopefully, the outcomes
will be better on that.

824
00:48:16,630 --> 00:48:19,620
So that's the various
types of electrodes.

825
00:48:19,620 --> 00:48:22,500
And, obviously, the
cochlear implant

826
00:48:22,500 --> 00:48:23,650
is the real winner here.

827
00:48:24,700 --> 00:48:30,750
And we have been having
readings-- Hi, Sheila-- we've

828
00:48:30,750 --> 00:48:32,550
been having readings
in our class,

829
00:48:32,550 --> 00:48:35,160
and I'll do a reading now
about the cochlear implant.

830
00:48:38,180 --> 00:48:41,880
This is from-- this is
not made into a book form

831
00:48:41,880 --> 00:48:50,320
yet because this is from the
esteemed academic publication

832
00:48:50,320 --> 00:48:54,055
called Yahoo
Finance, on the web.

833
00:48:55,370 --> 00:49:03,770
And this is dated
September 9, 2013.

834
00:49:03,770 --> 00:49:12,540
And the subject of this
column is the Lasker Award.

835
00:49:24,150 --> 00:49:25,671
So the Lasker
Award, does anybody

836
00:49:25,671 --> 00:49:26,920
know what the Lasker Award is?

837
00:49:26,920 --> 00:49:30,730
Sometimes, called the
American Nobel Prize,

838
00:49:30,730 --> 00:49:32,360
so it's a very
prestigious honor.

839
00:49:32,360 --> 00:49:35,670
It's given in several
different fields,

840
00:49:35,670 --> 00:49:42,740
mostly in medicine
and biomedical areas,

841
00:49:42,740 --> 00:49:45,160
and so there are sub-groups.

842
00:49:45,160 --> 00:49:47,800
And this one was given in
clinical medical research

843
00:49:47,800 --> 00:49:48,780
award.

844
00:49:48,780 --> 00:49:55,010
So the 2013 Lasker Clinical
Medical Research Award

845
00:49:55,010 --> 00:49:59,640
honors Graeme Clark, Ingeborg
Hochmair and Blake Wilson

846
00:49:59,640 --> 00:50:04,380
for developing the modern
cochlear implant, a device that

847
00:50:04,380 --> 00:50:07,770
bestows hearing on
profoundly deaf people.

848
00:50:07,770 --> 00:50:09,520
The apparatus has,
for the first time,

849
00:50:09,520 --> 00:50:12,570
substantially
restored a human sense

850
00:50:12,570 --> 00:50:14,080
with a medical intervention.

851
00:50:15,620 --> 00:50:17,160
Blah, blah, blah.

852
00:50:17,160 --> 00:50:20,230
Throughout the world today,
there are about 320,000 people

853
00:50:20,230 --> 00:50:22,330
outfitted with
cochlear implants.

854
00:50:22,330 --> 00:50:25,680
Most recipients can
talk on their cellphones

855
00:50:25,680 --> 00:50:29,835
and follow conversations in
relatively quiet environments,

856
00:50:29,835 --> 00:50:31,740
and an increasing
number of patients

857
00:50:31,740 --> 00:50:34,080
with severe age-related
hearing loss

858
00:50:34,080 --> 00:50:36,950
are taking advantage of
this marvelous invention.

859
00:50:36,950 --> 00:50:40,860
So the three people
here, two of them

860
00:50:40,860 --> 00:50:45,320
are actually founders of
cochlear implant companies.

861
00:50:45,320 --> 00:50:50,140
So you can think of Nobel Prizes
and these prize being awarded

862
00:50:50,140 --> 00:50:51,900
to people who made
big discoveries.

863
00:50:51,900 --> 00:50:56,020
And certainly, in the third
case, Blake Wilson did.

864
00:50:56,020 --> 00:51:00,530
But in the first two, it's
really conveying a technology

865
00:51:00,530 --> 00:51:04,460
to the masses that was
recognized by this award.

866
00:51:04,460 --> 00:51:08,220
So that's the 2013 Lasker Award.

867
00:51:08,220 --> 00:51:13,010
So let's look a little bit about
what a cochlear implant is,

868
00:51:13,010 --> 00:51:15,200
and that's shown in the
next couple of slides.

869
00:51:15,200 --> 00:51:21,260
So the cochlear implant
has an internal part, which

870
00:51:21,260 --> 00:51:25,310
is a series of electrodes
that go into the cochlea,

871
00:51:25,310 --> 00:51:31,200
and the electrode
comes out from here

872
00:51:31,200 --> 00:51:34,650
and goes into a
so-called internal coil--

873
00:51:34,650 --> 00:51:42,440
sorry about that-- and this is
sometimes called the receiver

874
00:51:42,440 --> 00:51:45,190
because it gets messages
from the external coil,

875
00:51:45,190 --> 00:51:49,050
or sometimes called the
transmitter, across the skin

876
00:51:49,050 --> 00:51:49,560
here.

877
00:51:49,560 --> 00:51:53,485
So there's skin between the
external and internal coils.

878
00:51:54,870 --> 00:51:57,130
On the outside, you
have a microphone

879
00:51:57,130 --> 00:52:02,410
which picks up the sound and
sends the microphone messages

880
00:52:02,410 --> 00:52:04,495
to a so-called speech processor.

881
00:52:05,640 --> 00:52:09,650
The speech processor
sends transforms

882
00:52:09,650 --> 00:52:14,770
that sound wave form into a
series of electrical pulses

883
00:52:14,770 --> 00:52:16,990
that are sent down
the electrodes

884
00:52:16,990 --> 00:52:19,120
and stimulate the
remaining auditory nerve

885
00:52:19,120 --> 00:52:20,820
fibers in the cochlea.

886
00:52:22,030 --> 00:52:26,070
So the cochlear implant has the
electrodes, the internal part,

887
00:52:26,070 --> 00:52:28,210
the external part, and
the speech processor

888
00:52:28,210 --> 00:52:29,325
and microphone.

889
00:52:31,410 --> 00:52:36,460
And I have a demonstration
cochlear implant here.

890
00:52:36,460 --> 00:52:39,070
And I'm going to pass it around.

891
00:52:39,070 --> 00:52:43,330
These things are very valuable,
so as demonstration models,

892
00:52:43,330 --> 00:52:44,680
they strip off the electrodes.

893
00:52:46,690 --> 00:52:48,550
So the part I'm
passing around is just

894
00:52:48,550 --> 00:52:50,990
this tube that goes
down here but not

895
00:52:50,990 --> 00:52:53,450
the electrodes
themselves, and I think

896
00:52:53,450 --> 00:52:57,190
it has the internal and
external coil, and obviously not

897
00:52:57,190 --> 00:52:59,140
the microphone or
the speech processor,

898
00:52:59,140 --> 00:53:02,270
so just to give you
an idea of the size.

899
00:53:02,270 --> 00:53:05,240
And I think this one,
the tube comes down,

900
00:53:05,240 --> 00:53:08,680
and it coils around a
little like the electrodes

901
00:53:08,680 --> 00:53:10,240
do as they coil in the cochlea.

902
00:53:13,250 --> 00:53:16,100
Now, this next slide
is pretty important

903
00:53:16,100 --> 00:53:18,230
because it shows the
electrodes coming

904
00:53:18,230 --> 00:53:20,410
into the cochlea in
a cutaway diagram.

905
00:53:21,950 --> 00:53:25,790
And so the electrodes come in
the basal turn of the cochlea.

906
00:53:25,790 --> 00:53:28,610
Remember there's an
area in the bone that

907
00:53:28,610 --> 00:53:31,940
has a little membrane over
it called the round window.

908
00:53:31,940 --> 00:53:35,280
Surgeons can go in there and
make a tear in round window

909
00:53:35,280 --> 00:53:37,300
and put the implant in there.

910
00:53:37,300 --> 00:53:39,290
Or, they can drill
a hole a little bit

911
00:53:39,290 --> 00:53:41,340
apical from the round
window and start

912
00:53:41,340 --> 00:53:43,370
in the base of
the cochlea, which

913
00:53:43,370 --> 00:53:47,700
is the big part of
the cochlea and then

914
00:53:47,700 --> 00:53:53,180
thread just by pushing
the electrode array more

915
00:53:53,180 --> 00:53:55,640
and more apical
into the cochlea.

916
00:53:55,640 --> 00:54:00,475
Now, the cochlea gets pretty
small as it goes very apically.

917
00:54:01,700 --> 00:54:07,020
And the electrodes don't fit
into the apical region so far.

918
00:54:07,020 --> 00:54:10,210
So current cochlear
implants only

919
00:54:10,210 --> 00:54:14,370
can be pushed in about to cover
the basal half of the cochlea,

920
00:54:14,370 --> 00:54:15,320
the basal 50%.

921
00:54:18,100 --> 00:54:20,400
So that seems like
a huge limitation.

922
00:54:20,400 --> 00:54:21,525
It's a bit of a limitation.

923
00:54:23,460 --> 00:54:25,710
Fortunately, it's not
an extreme limitation

924
00:54:25,710 --> 00:54:30,350
because the spiral ganglion
doesn't go all the way

925
00:54:30,350 --> 00:54:31,910
to the apical part
of the cochlea.

926
00:54:31,910 --> 00:54:35,090
The ganglion is where the cell
bodies of the auditory nerve

927
00:54:35,090 --> 00:54:36,090
is.

928
00:54:36,090 --> 00:54:40,790
And so there is ganglion that
ends about 3/4 of the way out,

929
00:54:40,790 --> 00:54:43,090
so the last quarter
wouldn't be helpful anyway.

930
00:54:45,330 --> 00:54:47,030
And here are the
various electrodes

931
00:54:47,030 --> 00:54:49,370
along the cochlear implant.

932
00:54:49,370 --> 00:54:52,655
And modern cochlear
implants have 22 electrodes.

933
00:54:57,710 --> 00:55:01,690
And they are hooked up.

934
00:55:01,690 --> 00:55:03,977
I'll show you how they're
hooked up in just a minute.

935
00:55:03,977 --> 00:55:06,310
Actually, I'll show you how
they're hooked up right now.

936
00:55:08,030 --> 00:55:12,940
The way this works is
the microphone signal

937
00:55:12,940 --> 00:55:16,210
comes into the speech
processor here,

938
00:55:16,210 --> 00:55:20,950
and the microphone signal is
split up into various bands.

939
00:55:20,950 --> 00:55:24,160
The microphone might pick
up only high frequency,

940
00:55:24,160 --> 00:55:27,170
in which case, this
band would be active,

941
00:55:27,170 --> 00:55:29,920
or it might pick up middle
frequencies, in which case

942
00:55:29,920 --> 00:55:34,180
these bands would be active, or
it might pick up low frequency

943
00:55:34,180 --> 00:55:35,810
or it might pick
up all frequencies.

944
00:55:36,860 --> 00:55:38,760
It depends on what the sound is.

945
00:55:40,060 --> 00:55:43,660
The output of those filters
is sent to some processing

946
00:55:43,660 --> 00:55:49,240
schemes, which eventually result
in little electric pulses,

947
00:55:49,240 --> 00:55:53,100
and those are shocks
that are sent down

948
00:55:53,100 --> 00:55:55,740
into the cochlear
implant electrodes.

949
00:55:55,740 --> 00:55:57,920
And this is supposed
to be-- actually

950
00:55:57,920 --> 00:55:59,795
something's not happening
here automatically.

951
00:56:01,320 --> 00:56:03,910
This is supposed to be
electrode number one, which

952
00:56:03,910 --> 00:56:08,540
is the most apical electrode,
and so on and so forth.

953
00:56:08,540 --> 00:56:12,030
And this scheme only
ends in electrode 18,

954
00:56:12,030 --> 00:56:15,820
so this is an old diagram
here because current cochlear

955
00:56:15,820 --> 00:56:16,670
implants have 22.

956
00:56:19,480 --> 00:56:23,320
So if you are hearing
very low frequencies,

957
00:56:23,320 --> 00:56:26,005
you're going to be stimulating
very apical electrodes.

958
00:56:27,430 --> 00:56:29,500
And if you're hearing
the highest frequencies,

959
00:56:29,500 --> 00:56:31,680
you're going to stimulate
the most basal electrode.

960
00:56:31,680 --> 00:56:35,250
And this is a recapitulation
of the place code

961
00:56:35,250 --> 00:56:42,340
for sound frequency where base
of the cochlear transduces

962
00:56:42,340 --> 00:56:45,940
in normal hearing, the high
frequencies, and the apex

963
00:56:45,940 --> 00:56:47,310
transduces the low frequencies.

964
00:56:47,310 --> 00:56:49,850
So when we said the
cochlear implant doesn't

965
00:56:49,850 --> 00:56:52,360
go all the way apically,
it can't fit there.

966
00:56:52,360 --> 00:56:53,260
So what happens?

967
00:56:53,260 --> 00:56:55,540
Well, the apex isn't
very well-stimulated

968
00:56:55,540 --> 00:56:56,740
in these designs.

969
00:56:58,470 --> 00:57:00,540
And so you will
hear descriptions

970
00:57:00,540 --> 00:57:05,080
of people who have their implant
turned on for the first time,

971
00:57:05,080 --> 00:57:07,210
and they'll say it
sounds like Donald Duck.

972
00:57:07,210 --> 00:57:09,730
It sounds really shrill
and very high-pitched.

973
00:57:10,900 --> 00:57:13,970
Well, a lot of the apex-- not
drawn here-- is not stimulated.

974
00:57:15,730 --> 00:57:17,090
So what happens?

975
00:57:17,090 --> 00:57:19,490
So these people,
after a month or two,

976
00:57:19,490 --> 00:57:22,040
say oh, yeah, it's
sounding better and better.

977
00:57:23,820 --> 00:57:27,980
And so there's some sort
of learning or plasticity

978
00:57:27,980 --> 00:57:30,090
that makes things settle
down, and the voices

979
00:57:30,090 --> 00:57:33,260
sound a little bit more
normal, maybe not normal,

980
00:57:33,260 --> 00:57:34,310
but more normal.

981
00:57:36,220 --> 00:57:39,510
And perfectly, as you saw
from the graph before,

982
00:57:39,510 --> 00:57:42,710
normal word
recognition scores can

983
00:57:42,710 --> 00:57:44,490
be achieved even though
you're stimulating

984
00:57:44,490 --> 00:57:46,010
just a portion of the cochlea.

985
00:57:48,830 --> 00:57:54,330
Now, I have a movie here,
and this gets on my nerves,

986
00:57:54,330 --> 00:57:56,400
but I want to show it
to you because this

987
00:57:56,400 --> 00:57:58,610
is what's shown to
patients who are

988
00:57:58,610 --> 00:57:59,990
about to get a cochlear implant.

989
00:58:01,240 --> 00:58:04,230
Gets on my nerves because you
see hair cells in here that

990
00:58:04,230 --> 00:58:06,610
have stereocilia that
are just waving around,

991
00:58:06,610 --> 00:58:08,575
but the stereocilia
are really rigid.

992
00:58:10,077 --> 00:58:12,160
But anyway, I thought it
would be interesting just

993
00:58:12,160 --> 00:58:19,380
to see what someone sees
when they are getting

994
00:58:19,380 --> 00:58:22,500
this stuff from a
cochlear implant.

995
00:58:22,500 --> 00:58:24,060
Let's see if this
movie will play.

996
00:58:29,549 --> 00:58:33,042
[VIDEO PLAYBACK]
In normal hearing,

997
00:58:33,042 --> 00:58:35,292
the hair in the inner ear--

998
00:58:35,292 --> 00:58:36,250
PROFESSOR: I hate this.

999
00:58:39,290 --> 00:58:41,230
I mean the best
membranes way over here.

1000
00:58:41,230 --> 00:58:42,176
The hair cells--

1001
00:58:42,176 --> 00:58:44,160
-The hearing nerve still
remains functional,

1002
00:58:44,160 --> 00:58:48,128
but the hair cells have
been lost or damaged.

1003
00:58:48,128 --> 00:58:52,592
In a cochlear implant system,
sound enters a microphone

1004
00:58:52,592 --> 00:58:55,072
and travels to an
external mini computer

1005
00:58:55,072 --> 00:58:57,056
called a sound processor.

1006
00:58:57,056 --> 00:58:59,040
The sound is processed
and converted

1007
00:58:59,040 --> 00:59:01,520
into digital information.

1008
00:59:01,520 --> 00:59:04,992
This digital information is
sent over a transmitter antenna

1009
00:59:04,992 --> 00:59:07,472
to the surgically implanted
part of the system.

1010
00:59:08,960 --> 00:59:11,936
The implant will turn
the sound information

1011
00:59:11,936 --> 00:59:14,912
into electrical signals
that travel down

1012
00:59:14,912 --> 00:59:17,888
to an electrode array inserted
into the tiny inner ear.

1013
00:59:22,848 --> 00:59:25,824
The electrodes directly
stimulate the auditory nerve,

1014
00:59:25,824 --> 00:59:28,304
sending sound
information to the brain.

1015
00:59:30,288 --> 00:59:33,760
Bypassing the damaged inner
ear, the cochlear implant

1016
00:59:33,760 --> 00:59:37,232
provides an entirely new
mechanism for hearing.

1017
00:59:40,208 --> 00:59:41,430
[END VIDEO PLAYBACK]

1018
00:59:41,430 --> 00:59:43,360
PROFESSOR: So that's
what the patient's see.

1019
00:59:44,690 --> 00:59:47,640
And how well does it work?

1020
00:59:47,640 --> 00:59:51,490
So we can ask a demonstrator
that we have today.

1021
00:59:51,490 --> 00:59:54,540
Sheila come on up in
front of the class.

1022
00:59:54,540 --> 01:00:00,855
This is Sheila [? Zu ?],
who is a MIT undergraduate.

1023
01:00:02,410 --> 01:00:03,900
You're a senior now, right?

1024
01:00:07,060 --> 01:00:09,625
What's your major at MIT?

1025
01:00:09,625 --> 01:00:11,970
SHEILA: I'm the only
in this major at MIT.

1026
01:00:11,970 --> 01:00:14,330
I'm in [INAUDIBLE]
technology and [? society ?]

1027
01:00:14,330 --> 01:00:17,470
and [INAUDIBLE] is a joint
major between Humanities

1028
01:00:17,470 --> 01:00:18,220
and [? Chinese. ?]

1029
01:00:18,892 --> 01:00:20,350
PROFESSOR: Are you
an overachiever?

1030
01:00:22,100 --> 01:00:23,025
SHEILA: I don't know.

1031
01:00:23,025 --> 01:00:23,525
Maybe.

1032
01:00:25,900 --> 01:00:28,260
PROFESSOR: So has
anybody in the class

1033
01:00:28,260 --> 01:00:31,035
ever spoken to a cochlear
implant user before?

1034
01:00:32,910 --> 01:00:34,380
SHEILA: I know some of them.

1035
01:00:34,380 --> 01:00:36,184
PROFESSOR: You know
some of these people?

1036
01:00:36,184 --> 01:00:39,420
SHEILA: We're in the same dorm.
[INAUDIBLE] in my sorority.

1037
01:00:39,420 --> 01:00:39,920
OK.

1038
01:00:39,920 --> 01:00:41,100
Great!

1039
01:00:41,100 --> 01:00:45,530
So we can do this
whatever way you want to.

1040
01:00:45,530 --> 01:00:48,240
You can ask Sheila
questions if you've already

1041
01:00:48,240 --> 01:00:49,287
asked them to her.

1042
01:00:49,287 --> 01:00:50,245
I'll ask her questions.

1043
01:00:51,947 --> 01:00:53,280
Does anybody have any questions?

1044
01:00:56,880 --> 01:00:57,380
Yes?

1045
01:00:57,380 --> 01:00:59,640
AUDIENCE: How old were you
when you got your implant?

1046
01:01:00,990 --> 01:01:04,015
SHEILA: So I was born
deaf, but I got implant

1047
01:01:04,015 --> 01:01:05,500
when I was 3 years old.

1048
01:01:07,280 --> 01:01:09,370
Actually, I got surgery
when I was 2 years old.

1049
01:01:09,370 --> 01:01:12,580
[INAUDIBLE] when
I was 3 years old.

1050
01:01:14,290 --> 01:01:16,210
PROFESSOR: So one
question I often

1051
01:01:16,210 --> 01:01:22,560
get about implants into children
is how young can a child be

1052
01:01:22,560 --> 01:01:24,660
and still be implanted
successfully.

1053
01:01:24,660 --> 01:01:27,520
So the surgeons at
Mass Eye and Ear

1054
01:01:27,520 --> 01:01:32,630
say that the cochlea is
adult size by age 1 and 1/2,

1055
01:01:32,630 --> 01:01:37,430
so typically, that's the age
when a person who is born deaf

1056
01:01:37,430 --> 01:01:39,570
is implanted these
days, age 1 and 1/2.

1057
01:01:39,570 --> 01:01:44,120
The idea to implant early
is so that the subject

1058
01:01:44,120 --> 01:01:47,000
can grow up and enjoy
normal hearing, especially

1059
01:01:47,000 --> 01:01:50,880
during a critical period for
language formation, which

1060
01:01:50,880 --> 01:01:54,680
was maybe starting at
1 and 1/2, 2 years old.

1061
01:01:54,680 --> 01:01:57,680
So if you implant a person
later, in their teens,

1062
01:01:57,680 --> 01:02:01,122
and they haven't
heard sound, they

1063
01:02:01,122 --> 01:02:05,520
have a lot worse chances of
acquiring normal language

1064
01:02:05,520 --> 01:02:09,388
skills than someone like Sheila
who has been implanted early.

1065
01:02:09,388 --> 01:02:12,570
So the trend is to try to
implant as early as possible.

1066
01:02:14,546 --> 01:02:18,127
SHEILA: I want to point out that
I may have been implanted when

1067
01:02:18,127 --> 01:02:19,980
I was 3 years old,
but I didn't start

1068
01:02:19,980 --> 01:02:22,450
speaking until I was
about 5 years old.

1069
01:02:22,450 --> 01:02:24,920
And I didn't start
learning math or learning

1070
01:02:24,920 --> 01:02:27,250
how to read until I was 7
years old, so I was really

1071
01:02:27,250 --> 01:02:28,516
delayed back then.

1072
01:02:32,260 --> 01:02:34,070
PROFESSOR: Did you
have a question?

1073
01:02:34,070 --> 01:02:35,820
AUDIENCE: So I was
just wondering, are you

1074
01:02:35,820 --> 01:02:37,910
like reading my lips right now?

1075
01:02:37,910 --> 01:02:39,070
SHEILA: Yes, I am.

1076
01:02:39,070 --> 01:02:42,780
So the way it works, I
have to see people's face,

1077
01:02:42,780 --> 01:02:45,900
like how to read their lips, and
I listen too at the same time.

1078
01:02:46,940 --> 01:02:50,670
I could read your lips alone,
but maybe not 100% accurate.

1079
01:02:51,706 --> 01:02:54,270
Or, if I don't look at you
lip, and listen to you,

1080
01:02:54,270 --> 01:02:56,690
maybe not really
understandable, so it's

1081
01:02:56,690 --> 01:02:59,790
like I have to read lips
and listen at the same time

1082
01:02:59,790 --> 01:03:01,770
in order to understand you.

1083
01:03:01,770 --> 01:03:06,570
PROFESSOR: But if you don't
read lips, for example,

1084
01:03:06,570 --> 01:03:09,220
in situations like
talking on the telephone,

1085
01:03:09,220 --> 01:03:11,270
can you understand
someone on the telephone?

1086
01:03:11,270 --> 01:03:13,445
SHEILA: It depends
on the person.

1087
01:03:13,445 --> 01:03:16,760
If I'm familiar with your voice,
like I know my dad's voice.

1088
01:03:16,760 --> 01:03:18,900
I can understand
him pretty well,

1089
01:03:18,900 --> 01:03:23,290
but if I'm talking to a stranger
on the phone, then maybe not.

1090
01:03:23,290 --> 01:03:25,955
And also, don't forget, there's
a lot of background noises,

1091
01:03:25,955 --> 01:03:28,968
so that makes it harder for me
to hear people on the phone.

1092
01:03:31,960 --> 01:03:36,440
PROFESSOR: When I-- let's say
about 10 years ago in my lab,

1093
01:03:36,440 --> 01:03:40,390
I hired a research assistant
who used a cochlear implant,

1094
01:03:40,390 --> 01:03:43,630
and she wanted me to
shave off my mustache.

1095
01:03:47,150 --> 01:03:49,880
It was because she had
a little trouble reading

1096
01:03:49,880 --> 01:03:52,070
my lips with my mustache.

1097
01:03:52,070 --> 01:03:56,010
Now, my wife also has told
me I should shave a mustache,

1098
01:03:56,010 --> 01:03:57,243
but she has normal hearing.

1099
01:04:00,624 --> 01:04:02,790
SHEILA: I actually
had a professor at MIT

1100
01:04:02,790 --> 01:04:06,000
when I was a freshman,
I comment one day I

1101
01:04:06,000 --> 01:04:07,820
had hard time understanding
him because he

1102
01:04:07,820 --> 01:04:08,736
had like a full beard.

1103
01:04:09,534 --> 01:04:11,552
Then, next day, he
shaved off everything.

1104
01:04:11,552 --> 01:04:14,444
So he came up to me, I
was like, who are you?

1105
01:04:16,836 --> 01:04:17,336
[INAUDIBLE]

1106
01:04:20,114 --> 01:04:21,280
PROFESSOR: That's very nice.

1107
01:04:21,280 --> 01:04:22,170
Wow, interesting!

1108
01:04:23,400 --> 01:04:27,360
I didn't shave off my mustache,
neither for my assistant,

1109
01:04:27,360 --> 01:04:28,612
nor for my wife.

1110
01:04:28,612 --> 01:04:30,070
SHEILA: [INAUDIBLE]
half is better.

1111
01:04:31,412 --> 01:04:32,120
PROFESSOR: Maybe.

1112
01:04:32,120 --> 01:04:32,620
Yeah.

1113
01:04:34,280 --> 01:04:41,690
So if an audiologist were to
test your speech comprehension,

1114
01:04:41,690 --> 01:04:44,880
do you think you'd
get every word correct

1115
01:04:44,880 --> 01:04:46,440
or do you think you'd miss some?

1116
01:04:47,500 --> 01:04:49,540
SHEILA: I think I
probably miss some words

1117
01:04:49,540 --> 01:04:52,600
or may not pronounce
some words correctly,

1118
01:04:52,600 --> 01:04:55,985
because the way I hear
words may sound differently

1119
01:04:55,985 --> 01:04:57,340
from what you hear.

1120
01:04:57,340 --> 01:04:59,020
And sometimes, in
English language,

1121
01:04:59,020 --> 01:05:02,560
some words don't sound exactly
the way it's written down.

1122
01:05:03,800 --> 01:05:07,600
So I think my speech is
not bad because, based

1123
01:05:07,600 --> 01:05:09,942
on my interaction
with people, they

1124
01:05:09,942 --> 01:05:11,566
seem to understand
me most of the time.

1125
01:05:14,006 --> 01:05:14,982
Yeah?

1126
01:05:14,982 --> 01:05:16,934
AUDIENCE: Do you know
any other languages?

1127
01:05:16,934 --> 01:05:19,362
SHEILA: I know another language.

1128
01:05:19,362 --> 01:05:19,862
Yeah.

1129
01:05:19,862 --> 01:05:21,920
I know a couple of languages.

1130
01:05:21,920 --> 01:05:23,920
I know American sign language.

1131
01:05:23,920 --> 01:05:26,880
I use it often to
help, in some cases,

1132
01:05:26,880 --> 01:05:29,040
when cochlear
implant don't work.

1133
01:05:29,040 --> 01:05:32,400
For example, if I'm
in a loud bar or party

1134
01:05:32,400 --> 01:05:34,977
and I can't hear people,
but if I use sign language,

1135
01:05:34,977 --> 01:05:35,810
I understand people.

1136
01:05:37,120 --> 01:05:39,196
I know British
sign language too,

1137
01:05:39,196 --> 01:05:40,570
but that's another
sign language.

1138
01:05:42,600 --> 01:05:46,180
PROFESSOR: So you mentioned
when you're in a party

1139
01:05:46,180 --> 01:05:50,650
and you can't hear people,
does that mean that there's

1140
01:05:50,650 --> 01:05:55,490
a lot of noise that
masks speakers and that's

1141
01:05:55,490 --> 01:05:57,964
a hard situation for you?

1142
01:05:57,964 --> 01:05:59,257
Right.

1143
01:05:59,257 --> 01:06:00,715
SHEILA: So like
the speaker's voice

1144
01:06:00,715 --> 01:06:05,210
will blend into other speakers
voices or background noises,

1145
01:06:05,210 --> 01:06:08,255
so I tend to rely on
lipreading or some other method

1146
01:06:08,255 --> 01:06:08,880
to communicate.

1147
01:06:11,442 --> 01:06:12,150
PROFESSOR: Right.

1148
01:06:12,150 --> 01:06:16,820
So for example, in
cochlear implants,

1149
01:06:16,820 --> 01:06:21,920
a common problem is when
there is an environment where

1150
01:06:21,920 --> 01:06:25,420
there's many, many
frequencies of sound,

1151
01:06:25,420 --> 01:06:28,790
like a crowded
restaurant or a party,

1152
01:06:28,790 --> 01:06:32,780
and there's one speaker that
you're trying to pay attention

1153
01:06:32,780 --> 01:06:38,460
to and the subject
gets overloaded

1154
01:06:38,460 --> 01:06:40,560
on every single electrode.

1155
01:06:40,560 --> 01:06:46,010
And so some kinds of
cochlear implant processors

1156
01:06:46,010 --> 01:06:50,680
try to circumvent that by trying
to pick out in the spectrum

1157
01:06:50,680 --> 01:06:53,420
the important peaks
of the spectrum.

1158
01:06:53,420 --> 01:06:55,810
So if you're listening
to the vowel aa,

1159
01:06:55,810 --> 01:06:57,220
you'd have three formants.

1160
01:06:58,660 --> 01:07:02,720
The processor tries to pick
out those formants and only

1161
01:07:02,720 --> 01:07:07,490
present electrodes
corresponding to those formants

1162
01:07:07,490 --> 01:07:10,610
and turn all the other
electrodes off so that there's

1163
01:07:10,610 --> 01:07:14,055
a huge difference between
where the formant is

1164
01:07:14,055 --> 01:07:15,660
and where the nothing is.

1165
01:07:15,660 --> 01:07:17,739
Really in theory, it's
nothing, but actually, it

1166
01:07:17,739 --> 01:07:18,905
could be a noisy background.

1167
01:07:20,050 --> 01:07:24,250
So that is one kind of
speech processor design.

1168
01:07:24,250 --> 01:07:27,750
It's called the speech
feature extractor, sometimes

1169
01:07:27,750 --> 01:07:28,880
the speak chip.

1170
01:07:28,880 --> 01:07:31,290
It's trying to pick
out formants so

1171
01:07:31,290 --> 01:07:33,460
that it can understand vowels.

1172
01:07:33,460 --> 01:07:37,090
And it's supposed to be less
sensitive to noise masking,

1173
01:07:37,090 --> 01:07:39,635
which is a huge problem
in cochlear implants.

1174
01:07:40,726 --> 01:07:44,450
A cochlear implant user doesn't
have the sharply tuned filter

1175
01:07:44,450 --> 01:07:46,910
of the normal
auditory nerve tuning

1176
01:07:46,910 --> 01:07:50,400
curve that normal
hearing people do.

1177
01:07:50,400 --> 01:07:52,280
What about listening to music?

1178
01:07:52,280 --> 01:07:54,419
Do you listen to music?

1179
01:07:54,419 --> 01:07:54,960
SHEILA: Yeah.

1180
01:07:54,960 --> 01:07:57,640
Like last month, I went
to hear Yo-Yo Ma play.

1181
01:07:57,640 --> 01:08:01,980
Like when-- I can hear
music, but I'm not sure.

1182
01:08:01,980 --> 01:08:04,680
I think I hear music
differently from you guys

1183
01:08:04,680 --> 01:08:06,856
because there's a whole
range of frequencies,

1184
01:08:06,856 --> 01:08:10,000
like you said, but yeah
I can listen to music.

1185
01:08:11,896 --> 01:08:14,266
AUDIENCE: How often do you
go to the doctor for updates?

1186
01:08:19,829 --> 01:08:21,670
SHEILA: How often do I go to--

1187
01:08:21,670 --> 01:08:22,700
AUDIENCE: You're doctor.

1188
01:08:22,700 --> 01:08:24,075
SHEILA: Oh, you
mean audiologist.

1189
01:08:25,080 --> 01:08:29,045
I see audiologist like
maybe once every year just

1190
01:08:29,045 --> 01:08:31,630
for a checkup and remapping.

1191
01:08:31,630 --> 01:08:34,970
PROFESSOR: So do
you get a remapping

1192
01:08:34,970 --> 01:08:36,979
or do they just bill
your insurance company?

1193
01:08:36,979 --> 01:08:37,520
SHEILA: Yeah.

1194
01:08:39,763 --> 01:08:40,388
PROFESSOR: Yes.

1195
01:08:40,388 --> 01:08:42,300
SHEILA: It's expensive.

1196
01:08:42,300 --> 01:08:44,590
PROFESSOR: But do
they-- do you know

1197
01:08:44,590 --> 01:08:48,600
if they change the mapping
for your electrodes?

1198
01:08:48,600 --> 01:08:51,630
SHEILA: Yeah, they change
it, but they told me

1199
01:08:51,630 --> 01:08:54,084
it's not really
a lot of changes.

1200
01:08:54,084 --> 01:08:57,180
So I think the older
you get, the less change

1201
01:08:57,180 --> 01:08:58,901
is made than when
you were younger.

1202
01:08:58,901 --> 01:08:59,942
PROFESSOR: Perhaps, yeah.

1203
01:09:01,170 --> 01:09:03,510
So that's interesting.

1204
01:09:03,510 --> 01:09:06,100
So how do they do that mapping?

1205
01:09:07,670 --> 01:09:13,410
Do they say here's electrode
1, and then here's electrode 2.

1206
01:09:13,410 --> 01:09:14,819
Which is higher?

1207
01:09:14,819 --> 01:09:15,700
Do they do that?

1208
01:09:15,700 --> 01:09:19,029
SHEILA: Yeah, so I had to go
into a special sound booth.

1209
01:09:19,029 --> 01:09:22,949
So it's like a cell that
is completely soundproof.

1210
01:09:24,010 --> 01:09:26,840
And they will test me
on a bunch of sounds

1211
01:09:26,840 --> 01:09:29,229
like saying stop
if it's too loud,

1212
01:09:29,229 --> 01:09:32,340
or which one is
louder or softer,

1213
01:09:32,340 --> 01:09:34,920
can you repeat words
after me, and so on.

1214
01:09:34,920 --> 01:09:39,700
And they use all of that
input to create a new map.

1215
01:09:39,700 --> 01:09:40,870
PROFESSOR: Interesting.

1216
01:09:40,870 --> 01:09:44,550
So apparently with
cochlear implant users,

1217
01:09:44,550 --> 01:09:46,450
the frequency mapping
of the electrodes

1218
01:09:46,450 --> 01:09:48,500
doesn't change in a big way.

1219
01:09:48,500 --> 01:09:51,210
But in the auditory
brain stem implant,

1220
01:09:51,210 --> 01:09:55,410
they go through yearly checkups
and, evidently, the mapping

1221
01:09:55,410 --> 01:09:57,415
can change a great deal.

1222
01:09:57,415 --> 01:09:59,400
So it's completely different.

1223
01:09:59,400 --> 01:10:02,730
In cochlear implants, usually
the most apical electrode

1224
01:10:02,730 --> 01:10:05,900
evokes the lowest
sensation of pitch

1225
01:10:05,900 --> 01:10:09,301
and more basal electrodes get
higher and higher sensations

1226
01:10:09,301 --> 01:10:09,800
of pitch.

1227
01:10:12,468 --> 01:10:14,509
AUDIENCE: How easy is it
for you to differentiate

1228
01:10:14,509 --> 01:10:15,982
between two voices?

1229
01:10:15,982 --> 01:10:20,892
Like if you didn't see who was
talking and if I said something

1230
01:10:20,892 --> 01:10:22,856
and then Professor
[? Brown ?] said something,

1231
01:10:22,856 --> 01:10:25,802
how different would our
voices sound to you?

1232
01:10:25,802 --> 01:10:30,010
SHEILA: His voice is deeper,
and you're farther away from me.

1233
01:10:30,010 --> 01:10:34,540
So I think I can tell the
difference between you two.

1234
01:10:34,540 --> 01:10:37,630
I can tell difference between
male and female voices.

1235
01:10:39,052 --> 01:10:39,760
PROFESSOR: Right.

1236
01:10:39,760 --> 01:10:41,920
Female voices sound
higher usually.

1237
01:10:41,920 --> 01:10:42,920
SHEILA: Higher pictched.

1238
01:10:42,920 --> 01:10:43,420
Yeah.

1239
01:10:45,434 --> 01:10:47,100
PROFESSOR: Do you
know Mandarin Chinese?

1240
01:10:48,535 --> 01:10:49,660
SHEILA: Yeah, a little bit.

1241
01:10:49,660 --> 01:10:51,740
I can speak some
Chinese, but not

1242
01:10:51,740 --> 01:10:56,130
so good because I haven't
used Chinese for a long time.

1243
01:10:56,130 --> 01:10:58,564
PROFESSOR: It's a
tonal language, right?

1244
01:10:58,564 --> 01:10:59,105
SHEILA: Yeah.

1245
01:10:59,105 --> 01:10:59,440
Oh my God!

1246
01:10:59,440 --> 01:11:00,731
PROFESSOR: Does that give you--

1247
01:11:03,465 --> 01:11:06,810
SHEILA: It's like I went
to China 4 years ago.

1248
01:11:06,810 --> 01:11:08,310
I stayed in China
for about a month.

1249
01:11:08,310 --> 01:11:09,890
So my grandma,
she couldn't speak

1250
01:11:09,890 --> 01:11:11,895
English, so I had to
speak to her in Chinese.

1251
01:11:13,100 --> 01:11:16,820
But it's interesting how
it's-- when I talk to people,

1252
01:11:16,820 --> 01:11:20,440
like when I speak myself, I have
to remember how use the tones,

1253
01:11:20,440 --> 01:11:24,141
but if I listen to them, I can't
tell the difference between

1254
01:11:24,141 --> 01:11:24,640
tone.

1255
01:11:24,640 --> 01:11:28,050
So what I do is I read
their lips and listen.

1256
01:11:28,050 --> 01:11:32,810
And I use context clues
like so if the sound goes

1257
01:11:32,810 --> 01:11:35,290
with this sound,
so I think those

1258
01:11:35,290 --> 01:11:37,945
sounds form a certain word.

1259
01:11:37,945 --> 01:11:40,740
That's how I did,
but I believe I

1260
01:11:40,740 --> 01:11:43,750
can learn Chinese with
a matter of practice

1261
01:11:43,750 --> 01:11:45,050
and getting used to the sound.

1262
01:11:46,762 --> 01:11:50,800
PROFESSOR: Apparently,
cochlear implant users

1263
01:11:50,800 --> 01:11:54,510
have a lot of problems
with melodic intervals,

1264
01:11:54,510 --> 01:11:58,110
octave matches, and
tonal languages.

1265
01:11:58,110 --> 01:12:02,360
The temporal code
for frequency that

1266
01:12:02,360 --> 01:12:05,370
helps us appreciate
musical intervals

1267
01:12:05,370 --> 01:12:08,670
is not present at all
in any cochlear implant

1268
01:12:08,670 --> 01:12:09,750
scheme that's used now.

1269
01:12:11,130 --> 01:12:15,210
So you only have the place
code for sound frequencies,

1270
01:12:15,210 --> 01:12:18,990
you don't have the timing code
in current generation cochlear

1271
01:12:18,990 --> 01:12:19,820
implant users.

1272
01:12:19,820 --> 01:12:22,970
And so the goal,
remember, is to allow

1273
01:12:22,970 --> 01:12:25,200
the users to understand speech.

1274
01:12:25,200 --> 01:12:30,830
It's not in terms of
recognizing musical intervals.

1275
01:12:30,830 --> 01:12:35,910
Now, if cochlear implant
companies were based in China,

1276
01:12:35,910 --> 01:12:38,980
maybe the goal of
understanding Mandarin Chinese,

1277
01:12:38,980 --> 01:12:42,425
which is total, would be
more important, but so far,

1278
01:12:42,425 --> 01:12:43,300
that hasn't happened.

1279
01:12:45,022 --> 01:12:46,438
AUDIENCE: Are you
more comfortable

1280
01:12:46,438 --> 01:12:49,896
with speaking with people
or are you more comfortable

1281
01:12:49,896 --> 01:12:52,370
with not speaking with people?

1282
01:12:52,370 --> 01:12:54,430
SHEILA: Well, I'm
more comfortable using

1283
01:12:54,430 --> 01:12:57,750
sign language, but I don't mind
going up in front of people

1284
01:12:57,750 --> 01:12:58,460
and speaking.

1285
01:13:04,360 --> 01:13:06,610
PROFESSOR: So one time,
I had a demonstrator

1286
01:13:06,610 --> 01:13:08,350
get asked this question.

1287
01:13:08,350 --> 01:13:10,110
What's the stupidest
thing you've ever

1288
01:13:10,110 --> 01:13:11,640
done with your cochlear implant?

1289
01:13:12,990 --> 01:13:15,510
And he had a
response right away.

1290
01:13:15,510 --> 01:13:19,490
He said when I first got my
implant, I went to the beach.

1291
01:13:19,490 --> 01:13:22,830
And I was 13 years old, and
I was a typical teenager.

1292
01:13:22,830 --> 01:13:25,615
And I saw someone else
with a cochlear implant,

1293
01:13:25,615 --> 01:13:26,990
and that was great
because it was

1294
01:13:26,990 --> 01:13:29,620
the first person
I had ever seen.

1295
01:13:29,620 --> 01:13:31,890
And so I said, let's
swap processors.

1296
01:13:33,860 --> 01:13:35,830
And that was actually
a very stupid thing

1297
01:13:35,830 --> 01:13:39,530
to do because each cochlear
implant user is not

1298
01:13:39,530 --> 01:13:43,290
only programmed for their
coding for frequency,

1299
01:13:43,290 --> 01:13:47,935
but they're coding for how much
shock goes into auditory nerve.

1300
01:13:49,200 --> 01:13:51,120
And some people
who have electrodes

1301
01:13:51,120 --> 01:13:54,770
close to the auditory nerve
don't need much current all,

1302
01:13:54,770 --> 01:13:58,060
but if your electrode is far
away you need a lot of current.

1303
01:13:58,060 --> 01:14:00,900
And this fellow got
a processor that

1304
01:14:00,900 --> 01:14:02,980
had been dialed in
a lot of current,

1305
01:14:02,980 --> 01:14:05,130
and so he got a big
severe shock when

1306
01:14:05,130 --> 01:14:08,380
you turn the other person's
cochlear implant on.

1307
01:14:08,380 --> 01:14:13,025
So that's something they
tell you not to do, right?

1308
01:14:15,320 --> 01:14:17,410
SHEILA: I don't think
anybody told me that.

1309
01:14:17,410 --> 01:14:20,320
But clearly I was like,
OK, total wipe out.

1310
01:14:20,320 --> 01:14:21,252
That's a bad shock.

1311
01:14:21,252 --> 01:14:22,460
PROFESSOR: You did that also?

1312
01:14:22,460 --> 01:14:23,832
SHEILA: Well, we both did.

1313
01:14:23,832 --> 01:14:25,040
We exchange at the same time.

1314
01:14:28,850 --> 01:14:31,450
PROFESSOR: Kids don't usually
listen to adults, right?

1315
01:14:34,600 --> 01:14:37,230
So are there a lot
of students at MIT

1316
01:14:37,230 --> 01:14:38,650
who use a cochlear implant?

1317
01:14:40,336 --> 01:14:43,805
SHEILA: So far, by now,
I think I'm the only one.

1318
01:14:43,805 --> 01:14:47,210
But last year, there were
two of us, but he graduated.

1319
01:14:47,210 --> 01:14:48,950
So this year, I'm the only one.

1320
01:14:48,950 --> 01:14:50,620
But I'm not the
only deaf student.

1321
01:14:50,620 --> 01:14:52,680
There are like two or
three other deaf student,

1322
01:14:52,680 --> 01:14:54,432
but they wear hearing aids.

1323
01:14:57,700 --> 01:14:59,040
PROFESSOR: Question.

1324
01:14:59,040 --> 01:15:01,200
AUDIENCE: How often
do you turn it off--

1325
01:15:01,200 --> 01:15:03,420
or how often is it off?

1326
01:15:03,420 --> 01:15:05,580
SHEILA: Oh, I turn
it off every night.

1327
01:15:05,580 --> 01:15:08,372
[INAUDIBLE] I go to
bed because there's

1328
01:15:08,372 --> 01:15:09,830
no point when I go
to sleep, right?

1329
01:15:11,141 --> 01:15:13,010
And when I take a
shower or go swimming

1330
01:15:13,010 --> 01:15:16,680
or if I want to have
a [INAUDIBLE] day.

1331
01:15:16,680 --> 01:15:18,970
On campus sometimes,
I would get so tired

1332
01:15:18,970 --> 01:15:22,079
of listening to people,
I would just take it off.

1333
01:15:24,450 --> 01:15:26,780
PROFESSOR: Which classes
do you turn it on

1334
01:15:26,780 --> 01:15:28,595
and which classes
do you turn it off?

1335
01:15:32,000 --> 01:15:32,500
That's OK.

1336
01:15:34,940 --> 01:15:37,284
How long does your battery last?

1337
01:15:37,284 --> 01:15:42,390
SHEILA: My battery last like 3
or 4 days, disposable battery,

1338
01:15:42,390 --> 01:15:46,280
3 or 4 days, but rechargeable
battery it's like one day.

1339
01:15:49,280 --> 01:15:51,470
PROFESSOR: And do
you have an implant

1340
01:15:51,470 --> 01:15:54,450
on one side only, or both sides?

1341
01:15:55,920 --> 01:15:58,370
SHEILA: In my right
ear, it's just one side.

1342
01:15:58,370 --> 01:16:01,300
PROFESSOR: Are you going
to get it in the other ear?

1343
01:16:01,300 --> 01:16:04,150
SHEILA: I'm not so sure
because it takes time.

1344
01:16:05,310 --> 01:16:09,480
I had to go through a surgery,
to see doctors, and so

1345
01:16:09,480 --> 01:16:12,570
on, so I'm not sure at that
time because I'm so busy at MIT.

1346
01:16:16,305 --> 01:16:19,275
AUDIENCE: What kind of alarm
clock helps you to wake up?

1347
01:16:24,740 --> 01:16:27,740
PROFESSOR: Do you
have an alarm clock?

1348
01:16:27,740 --> 01:16:28,740
SHEILA: Oh, yes.

1349
01:16:28,740 --> 01:16:31,300
I have a special alarm clock.

1350
01:16:31,300 --> 01:16:34,270
So I know you guys
use a typical alarm.

1351
01:16:34,270 --> 01:16:35,290
They make loud noises.

1352
01:16:35,290 --> 01:16:40,760
But for me, I use alarm
clock and a flashing lamp,

1353
01:16:40,760 --> 01:16:44,785
so it just flash light on
me that helps to wake me up.

1354
01:16:44,785 --> 01:16:47,440
But some other people say
it doesn't work for them,

1355
01:16:47,440 --> 01:16:49,770
so what they do, they take
a small vibrator thing

1356
01:16:49,770 --> 01:16:52,200
and tuck it under their
pillow or mattress,

1357
01:16:52,200 --> 01:16:55,650
so it's like that then
shocks them awake.

1358
01:17:03,060 --> 01:17:04,990
PROFESSOR: What other
kinds of problems

1359
01:17:04,990 --> 01:17:07,895
do you have with your
implant besides noise?

1360
01:17:13,190 --> 01:17:15,946
SHEILA: I wish it was really
waterproof because if I

1361
01:17:15,946 --> 01:17:19,240
go swimming with my buddies
who are not deaf, then

1362
01:17:19,240 --> 01:17:20,500
how can I hear them.

1363
01:17:21,580 --> 01:17:24,260
But right now, it's
like a computer,

1364
01:17:24,260 --> 01:17:26,730
so obviously, I can't
just jump into water.

1365
01:17:30,538 --> 01:17:33,673
AUDIENCE: I was going to ask
who taught you sign language.

1366
01:17:33,673 --> 01:17:35,298
SHEILA: Do you know
some sign language?

1367
01:17:35,298 --> 01:17:37,131
AUDIENCE: A little, but
where did you learn?

1368
01:17:39,080 --> 01:17:42,365
SHEILA: [INAUDIBLE] I learned
when I was here at MIT.

1369
01:17:43,406 --> 01:17:44,930
That was about
like two years ago,

1370
01:17:44,930 --> 01:17:47,622
so I took a class at Harvard.

1371
01:17:47,622 --> 01:17:49,580
And then from there, I
met a lot of deaf people

1372
01:17:49,580 --> 01:17:53,190
here at MIT and
outside of MIT, so I

1373
01:17:53,190 --> 01:17:55,760
was able to be comfortable
in sign language.

1374
01:17:55,760 --> 01:17:56,450
I don't know.

1375
01:17:56,450 --> 01:17:57,908
I guess it's not
really hard for me

1376
01:17:57,908 --> 01:17:59,660
to learn sign
language compared to,

1377
01:17:59,660 --> 01:18:03,090
let's say Spanish, because
it's more official.

1378
01:18:03,090 --> 01:18:04,970
You don't need to
listen or speak,

1379
01:18:04,970 --> 01:18:08,416
so it's really like all
hands and [INAUDIBLE].

1380
01:18:08,416 --> 01:18:11,180
So it was pretty natural
for me to pick it up.

1381
01:18:12,980 --> 01:18:16,690
And I use sign language on a
daily basis with my boyfriend

1382
01:18:16,690 --> 01:18:21,490
or with my friends or whenever
I ASL interpreter for my class.

1383
01:18:23,460 --> 01:18:26,470
PROFESSOR: So you often
have an ASL interpreter?

1384
01:18:26,470 --> 01:18:29,580
SHEILA: Yeah, not all, but
it depends on the class.

1385
01:18:29,580 --> 01:18:34,030
For example, if the class is
math or science lecture based,

1386
01:18:34,030 --> 01:18:37,690
like one hour long lecture,
then I use [INAUDIBLE]

1387
01:18:37,690 --> 01:18:39,610
like real time
closed captioning.

1388
01:18:39,610 --> 01:18:42,690
Someone sit next to me,
and on the computer screen,

1389
01:18:42,690 --> 01:18:45,380
I read whatever professor
saying in real time,

1390
01:18:45,380 --> 01:18:46,880
and that person
type out everything.

1391
01:18:48,120 --> 01:18:52,930
Another class, like more of
a lab or a hands on class

1392
01:18:52,930 --> 01:18:55,980
or more moving around,
then I use ASL interpreter

1393
01:18:55,980 --> 01:18:59,248
because it's just awkward to
carry around a laptop reading

1394
01:18:59,248 --> 01:19:00,224
words on a screen.

1395
01:19:06,742 --> 01:19:08,950
PROFESSOR: What do you want
to do after you graduate?

1396
01:19:10,676 --> 01:19:12,800
SHEILA: Right now, I'm
applying to one Ph.d program

1397
01:19:12,800 --> 01:19:15,730
at Harvard that's a
program he is a part of,

1398
01:19:15,730 --> 01:19:19,750
so he may be my
professor next year even.

1399
01:19:19,750 --> 01:19:20,690
PROFESSOR: Yeah.

1400
01:19:20,690 --> 01:19:21,420
If you graduate.

1401
01:19:28,910 --> 01:19:30,150
What's the program?

1402
01:19:30,150 --> 01:19:31,630
This is a little sales pitch.

1403
01:19:31,630 --> 01:19:33,031
You can tell them about it.

1404
01:19:34,432 --> 01:19:36,460
SHEILA: The program
is part of Harvard,

1405
01:19:36,460 --> 01:19:38,820
but it was a part of MIT before.

1406
01:19:38,820 --> 01:19:43,010
But it's a Ph.d program
called Speech and Hearing

1407
01:19:43,010 --> 01:19:44,660
Bioscience and Technology.

1408
01:19:44,660 --> 01:19:45,202
Right?

1409
01:19:45,202 --> 01:19:45,910
PROFESSOR: Right.

1410
01:19:45,910 --> 01:19:48,890
SHEILA: And it's a program
that focus on hearing, cochlear

1411
01:19:48,890 --> 01:19:50,880
implant, hearing
aids, or anything

1412
01:19:50,880 --> 01:19:52,530
related to hearing and speech.

1413
01:19:54,018 --> 01:19:56,120
So right now, I'm
applying to that program.

1414
01:19:56,120 --> 01:19:58,400
We'll see how it goes.

1415
01:19:58,400 --> 01:19:59,066
PROFESSOR: Good.

1416
01:20:02,503 --> 01:20:05,449
AUDIENCE: This is personal,
but did your boyfriend already

1417
01:20:05,449 --> 01:20:06,930
know sign language?

1418
01:20:06,930 --> 01:20:09,415
SHEILA: Oh, he's deaf himself,
so he knows sign language.

1419
01:20:09,415 --> 01:20:10,180
But he's like me.

1420
01:20:10,180 --> 01:20:12,200
He could speak and sign.

1421
01:20:12,200 --> 01:20:13,705
But difference is
he had cochlear--

1422
01:20:13,705 --> 01:20:16,387
no wait-- he had hearing
aid, I have cochlear implant.

1423
01:20:20,379 --> 01:20:25,369
AUDIENCE: Do you think that
you've become a faster reader?

1424
01:20:25,369 --> 01:20:27,864
Like do you think you're faster
at reading than most people

1425
01:20:27,864 --> 01:20:29,860
because you rely on it more?

1426
01:20:29,860 --> 01:20:31,356
SHEILA: I would be more what?

1427
01:20:31,356 --> 01:20:31,856
Faster?

1428
01:20:31,856 --> 01:20:33,022
AUDIENCE: Faster at reading.

1429
01:20:33,022 --> 01:20:34,850
SHEILA: Faster at reading lips?

1430
01:20:34,850 --> 01:20:38,343
AUDIENCE: Like reading words
on a screen or reading text.

1431
01:20:39,370 --> 01:20:40,790
SHEILA: That's a good question.

1432
01:20:40,790 --> 01:20:42,590
I never thought of that.

1433
01:20:42,590 --> 01:20:45,245
It's a possibility because
yeah, you're right.

1434
01:20:45,245 --> 01:20:47,469
Have you seen it in person?

1435
01:20:47,469 --> 01:20:48,635
AUDIENCE: I haven't seen it.

1436
01:20:48,635 --> 01:20:49,801
SHEILA: You haven't seen it.

1437
01:20:49,801 --> 01:20:51,610
So it's like on
that comp screen,

1438
01:20:51,610 --> 01:20:53,660
where she type out
words really fast.

1439
01:20:53,660 --> 01:20:55,520
So I have to read fast.

1440
01:20:55,520 --> 01:20:58,170
But after one hour, I
got too tired to read,

1441
01:20:58,170 --> 01:21:00,370
so I just look around the room.

1442
01:21:03,250 --> 01:21:06,130
The good thing is after class,
she send me a transcript,

1443
01:21:06,130 --> 01:21:07,755
so I will go back
and look at it again.

1444
01:21:08,970 --> 01:21:11,805
So I mean, it's really tiring
to look at computer screen,

1445
01:21:11,805 --> 01:21:14,593
for one hour straight,
reading words really quickly.

1446
01:21:20,887 --> 01:21:21,470
PROFESSOR: OK.

1447
01:21:21,470 --> 01:21:23,500
So the cochlear
implant is sometimes

1448
01:21:23,500 --> 01:21:27,350
called the most successful
neural prosthesis,

1449
01:21:27,350 --> 01:21:28,980
and here we have an example.

1450
01:21:31,230 --> 01:21:33,718
So let's give Sheila a hand.

1451
01:21:33,718 --> 01:21:35,710
Thank you very much for coming.

1452
01:21:37,710 --> 01:21:40,445
And we'll talk next time
about brain stem reflexes.

1453
01:21:40,445 --> 01:21:44,540
So we'll hang around if you
have any other questions.