~Chapter 11 - Lecture Section 11.3

Question 1

The Cochlea acts as a ___, meaning that vibrations and fluid pressure along the Cochlea act to ___ frequencies.

Answer 1

hydrodynamical frequency analyzer // analyze

Question 2

How is the Cochlea able to act as a hydrodynamical frequency analyzer?

Answer 2

Through Passive mechanical properties and Active Mechanics of the outer hair cells. Phase locked firing of neurons also contributes .

Question 3

Our consideration of the Passive mechanical properties of the Cochlea starts with nobel Prize winner ___.

Answer 3

Von Beksey

Question 4

Von Beksey took human and animal cadavers, and dissected the ___ ear away and drilled a hole in the ___. He used a microscope to peer into this hole, and would place sounds to the ear and would use a ___ and ___ attached to the Cochlea to try to see how the Basilar Membrane was vibrating.

Answer 4

outer middle // Cochlea / strobe light // camera

Question 5

Through his dissections, Von Beksey found the Basilar Membrane was ___ and ___ at the base, and quite ___ and ___ at the Apex.

Answer 5

narrow // stiff // narrow // wide // floppy

Question 6

Von Beksey observed that when he played high frequency sounds it caused vibrations to occur near the ___.

Answer 6

base

Question 7

Von Beksey observed that when he played low frequency sounds it caused vibrations to occur near the ___.

Answer 7

Apex

Question 8

Von Beksey found that acoustic energy propagation (this is just vibrations) progressively ___ until the wave essentially stops with all the energy piling up/bunching up to maximally vibrate at a particular characteristic location of the ___. This characteristic location would differ for ___.

Answer 8

slow // Basilar Membrane // different frequencies

Question 9

Each location along the Basilar Membrane oscillates best to a ___, this is largely determined by the ___.

Answer 9

characteristic frequency // membrane stiffness

Question 10

___Hz gives the most movement in the Apex of the Basilar Membrane.

Answer 10

2,000

Question 11

If there are big vibrations, that means that the hair cells that are embedded in the Organ of Corti that are sitting on this part of the Basilar Membrane, are going to shake back and forth ___, and those are going to be causing this Depolarization and Hyperpolarization oscillation, so they’re gonna ___ very easily. The ones that are only wiggling a little bit ___ going to be activated much.

Answer 11

a lot // transduce // are not

Question 12

The characteristic frequency ___ as stiffness ___. So at the Base, high stiffness = ___ frequencies. At the Apex, low stiffness = ___ frequencies

Answer 12

decreases // decreases // high // low

Question 13

The propagation of the acoustic energy along the Basilar Membrane can be summarized by the ___.

Answer 13

Envelope of the traveling wave/maximum excursion

Question 14

Where the peak of the envelope lies is where the hair cells will be ___ activated. The peak of the envelope occurs at a ___ place along the Basilar Membrane for each frequency.

Answer 14

maximally // different

Question 15

Hair cells are most perturbed at the ___ of the envelope.

Answer 15

peak

Question 16

The frequency of sound that is being played to the Cochlea can be coded neuronally as the location of ___ along the basilar membrane.

Answer 16

peak deflection

Question 17

The Cochlea can tell by knowing which hair cells are activated what the ___ of the sound is. If all the hair cells near the Apex are being activated, that means it’s a ___ pitch sound. If hair cells near the Base are being maximally activated, that is going to be a very ___ frequency.

Answer 17

frequency // low // high

Question 18

The peaks in the Cochlea occur for ___, but the Cochlea can also have multiple peaks in response to ___.

Answer 18

simple Pure Tones // Complex Tones

Question 19

The Cochlea acts like a filter for both ___ and ___.

Answer 19

Simple // Complex Tones

Question 20

If we play a Complex Tone, which consists of 440, 880, and 1320Hz, when we get to the Basilar Membrane, there will be ___ distinct peaks for ___ of those components within the Complex Tones, these are the ___. This is what is meant by ___, it separates out the different frequencies in Complex Tones in order to activate different lines going to the brain.

Answer 20

three // each one // Harmonics // Hydrodynamical Frequency Analyzer //

Question 21

The separation of Components the way a Prism can separate white light into its different wavelengths, sometimes makes the Cochlea be called an ___. The Basilar Membrane is a ___, sometimes called an “auditory prism”.

Answer 21

Auditory Prism // frequency analyzer

Question 22

There is abundant evidence for ___.

Answer 22

Von Bekesy’s Place Theory

Question 23

What is a Tonotopic Map?

Answer 23

An ordered map of characteristic frequencies along the length of the Cochlea

Question 24

If recordings are made of the electrical activity of ___ or ___ you get a Tonotopic Map.

Answer 24

Auditory nerve fibres // individual hair-cells

Question 25

Auditory nerve fibres that are coming from the Base respond best to ___ frequencies, and Auditory Nerve Fibres that are coming from the Apex respond best to ___ frequencies.

Answer 25

high // low

Question 26

Characterizing the frequency responses of individual hair cells or Auditory nerve fibres is kind of like when we were studying the visual system and we would present ___ to a visual cortex neuron and you would measure the spike rates.

Answer 26

different orientations

Question 27

For the auditory system, recall that you will still get some hair cell activation even if it's further away from the ___ of the envelope of the travelling wave. So you will still get some responses to frequencies that the cells ___, so instead, the way auditory hair cells and auditory nerve fibres are characterized is by measuring the ___, and the ___ the threshold the more sensitive the cell is to that frequency.

Answer 27

peak // don’t prefer // threshold // lower

Question 28

What is Characteristic Frequency (CF)?

Answer 28

Characteristic Frequency (CF) is the point on the frequency tuning curve that has the lowest threshold

Question 29

A key for the Von Bekesy Place Theory is that the Characteristic Frequency changes in an ___, moving from the ___ to the ___. So when you record from neurons near the Base, they will have a CF that is very ___, and neurons near the Apex, auditory nerve fibres or auditory hair cells, will have a ___ CF.

Answer 29

orderly manner // Base // Apex // high // low-frequency

Question 30

Curves become ___ at higher frequencies, this only works when you use a linear x-axis. This is important for ___.

Answer 30

wider // pitch perception

Question 31

The ___ of hair cells along the Cochlea has enabled a Bionic Ear to be put into use. Bionic Ears are possible because of the ___ in the Cochlea.

Answer 31

Tonotopic arrangement // Tonotopic Map

Question 32

An Electronic Cochlear implant that allows those who either have ___ or ___ to hear again.

Answer 32

congenital deafness // acquired deafness

Question 33

In a Bionic Ear, there is an ___ that is fed through the boney tubes of the ___, it coils around such that near the end of the electrode that is stimulating cells near the ___ for low-frequency sounds, and at the back of the electrode where it's just entering, that is near the ___ for high-frequency sounds. Electrical stimulation through each one of the electrode sites bypasses damaged hair cells to activate the ___ directly and can produce a fairly sophisticated ___ of pitch.

Answer 33

electrode // Cochlea // Apex // Base // auditory nerve fibres // representation

Question 34

Bionic Ears stimulate the ___ and ___, which then directly activate the ___ to produce a sophisticated representation of ___.

Answer 34

Apex // Base // auditory nerve fibres // pitch

Question 35

Where was the first Bionic Ear made, and how long have they been around?

Answer 35

Australia, and they have been around for at least 20 years

Question 36

In the first few models of Bionic Ears, what was hearing like?

Answer 36

There was only a few frequencies in early models, so the sound was blips and blops and difficult to make out, so it was coupled with lip-reading.

Question 37

What do more modern versions of Bionic Ears feel like?

Answer 37

As more channels were added in later versions it would actually start to sound like digitized speech sounds

Question 38

Some parts of ___ don’t work with new evidence.

Answer 38

Place Theory

Question 39

Von Bekesy’s mechanical model of the Cochlea predicts that there will be ___ discrimination between tones that have very similar envelopes of the travelling wave. Yet, psychophysical evidence shows that we are ___ at distinguishing tones of ___.

Answer 39

poor // good // similar frequencies

Question 40

Can humans distinguish tones of similar frequencies?

Answer 40

Yes

Question 41

When animal experimentation was able to film living Basilar Membranes, these living Basilar Membranes showed ___ in their vibrational envelopes than previously measured from cadavers by Von Beksey.

Answer 41

sharper peaks

Question 42

The Cochlea can emit a sound called ___. This can be heard in ___ ears, and sounds like a ___ noise

Answer 42

Otoacoustic Emissions // dogs // buzzing

Question 43

Healthy Basilar membranes show that the Outer hair cells respond to sound by changing their ___. It’s a tiny change, maybe ___ of its length

Answer 43

length // 5%

Question 44

This contraction of Outer hair cells in response to sound is called the ___.

Answer 44

Motile Response

Question 45

The Inner hair cells are always ___, and they are for sending sound info to the ___, but the Outer hair cells that change length are responsible for the ____.

Answer 45

the same length // Central Nervous System // Motile Response

Question 46

The Inner hair cells carry ___. These send ___ neural output to all the ___, that's important for gathering a bunch of info about the stimulus.

Answer 46

sound information // diverging // Auditory nerve fibres

Question 47

The Outer hair cells are providing the ___. They don’t have to be that precise, they are sending ___ into a few auditory nerve fibres.

Answer 47

Motile Response // converging inputs

Question 48

The Motile Response is triggered by either ___ of the ___, or it can be controlled with ___, so from the ___ to the ear.

Answer 48

deflection // Cilia // Central Feedback // brain

Question 49

Deflection of the Cilia: There is a protein that lines the cell walls of these cell walls called ___, and it binds ___ in its ___.

Answer 49

Prestin // Chloride ions (Cl-) // resting state/Hyperpolarized state

Question 50

When there is a deflection towards the ___ side of the Cilia, and you have ___ of the hair cell, the Prestin protein ___ the Cl ions and it ___ and ___, which leads to this pulling up or shrinking of the ___.

Answer 50

long // Depolarization // unbinds // contracts // shrinks // hair cell

Question 51

You get oscillation between when the hair cells are long, and when they deflect, they pull up on the Basilar Membrane, this is like an ___ of whatever sound is already vibrating the membrane. That is why the Cilia of the outer hair cells have to be attached to the ___, they have to be able to pull on it and be connected. It’s like they are doing little chin-ups, pulling themselves and the entire basilar membrane up to amplify the oscillations that are already present to cause the deflection of the Cilia in the first place.

Answer 51

amplification // Tectorial Membrane

Question 52

The Motile Response ___ and ___ ___ of the basilar membrane to create ___ peaks.

Answer 52

reinforces // shapes // vibrations // sharper

Question 53

The Motile Response is sometimes called the ___.

Answer 53

Cochlear Amplifier

Question 54

When the Basilar Membrane has a normal response with the Cochlear Amplifier present, in response to a low pitch sound, it has a travelling wave envelope that has a ___ peak.

Answer 54

very sharp

Question 55

When the Basilar Membrane is treated with Furosemide, it removes the ___. Now, in response to a low pitch sound, we see now that the peak is not only ___, but it's also ___, so there's a ___ activation of all the hair cells, but that activation is ___.

Answer 55

Motile Response/Cochlear Amplifier // much lower // broader // broader // weaker

Question 56

Furosemide is a ___, which poisons the ___ and causes it to no longer work, this can lead to ___.

Answer 56

loop diuretic // Motile Response // permanent hearing loss

Question 57

How do we code for frequency (pitch)?

Answer 57

Place Code and Timing Code

Question 58

What is Place Code?

Answer 58

Neurons in the Basilar membrane code different frequencies via their location along the length of the Basilar Membrane

Question 59

Place Code: Hair cells that are close to the ___ will encode high frequencies, and Hair cells that are close to the ___ will encode low frequencies.

Answer 59

Base // Apex

Question 60

As the Basilar Membrane is going up and down, the ___ of the hair cells are wagging back and forth at the frequency of the ___, and what is created is a ___.

Answer 60

Cilia // sound stimulus // Timing Code

Question 61

What is Timing Code?

Answer 61

The Frequency of the sound is reflected in the firing of the neuron(s), the pattern of firing.

Question 62

Timing Code: Every time the hair cells are deflected to the ___ there is a lack of firing.

Answer 62

short side/are Hyperpolarized

Question 63

Timing Code: every time the hair cells are deflected to the ___ there is a burst of firing.

Answer 63

long side/ are Depolarizing

Question 64

What is Phase Locking?

Answer 64

The firing of neurons in synchrony with the phase of the stimulus.

Question 65

For low frequency sounds, a single neuron could keep track of the Oscillations very well, this is referred to as ___.

Answer 65

Phase Locking

Question 66

The firing of the single action potential always ___ the ___ of the stimulus. This is fine for ___ frequencies.

Answer 66

matches // peak // low

Question 67

Cells are known to fire ___spikes/s

Answer 67

20-200

Question 68

When you start to increase the frequency in the ___Hz range, a single neuron cannot fire this quickly due to its ___, and might start to miss ___.

Answer 68

700-1,000 // Absolute Refractory Period // cycles

Question 69

How can the auditory system compensate for the Absolute Refractory Period?

Answer 69

The Volley Principle

Question 70

Single fibres might catch every few peaks, but then it has the other fibres that will fire at that peak that they missed, this is referred to as the ___.

Answer 70

Volley Principle

Question 71

The Volley Principle is possible due to ___ hair cells sending ___ projections to many auditory nerve fibres.

Answer 71

Inner // Diverging

Question 72

When you record from many fibres over time, the population oscillation follows ___ frequencies. This can overcome the ___ of these auditory nerve fibres and work up to about ___Hz, which is way faster than the Absolute Refractory Period would allow for ___ neuron.

Answer 72

higher // Absolute Refractory Period // 1,000-5,000 // a single

Question 73

The Volley Principle allowing the timing code to extend up to ___Hz allows human speech to be encoded not only by the ___ but also by the ___.

Answer 73

5,000 // Place Code // Timing Code