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Survey of the Senses > Midterm 1 - Topic 3 > Flashcards

Midterm 1 - Topic 3 Flashcards

1
Q

What does Dr. Voyer refer to the auditory system as?

A

“An evolutionary triumph of miniaturization”

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2
Q

What is the auditory stimulus?

A

Sound wave

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3
Q

What is sound?
Explain

A

Auditory stimuli are caused by the displacement of an elastic medium
Vibrations make air molecules collide with each other
The sound wave is caused by the alternation of compression and rarefaction of the air molecules

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4
Q

Briefly, what is sound?

A

Small changes in air pressure

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5
Q

Frequency

A

The rate at which areas of compression and rarefaction (aka cycles) alternate determines frequency
# of cycles a sound completes in 1 second –> measured in Hz/cycles per second

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6
Q

What does frequency correspond to?

A

Psychological experience of pitch (subjective dimension)
High frequency usually means that the sound source vibrates more frequently than in the case of low frequency

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7
Q

Human range of frequencies heard

A

20 Hz - 20,000 Hz

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8
Q

Human lowest absolute threshold for frequency

A

2000 Hz - 5000 Hz

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9
Q

Frequency difference threshold
Weber’s fraction

A

At its best for sounds in the intermediate frequency range (500-2000 Hz)
As small as 0.3%

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10
Q

Amplitude

A

Amount of compression determines intensity
Amplitude = difference between compression and rarefaction

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11
Q

Amplitude

A

A high amplitude sound moves the eardrum more than a low amplitude sound
Reflects sound pressure and it is measures in dynes/cm^2

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12
Q

Logarithmic scale of sound pressures relative to the threshold pressure

A

Measure of sound pressure level (SPL), measured in decibels (dB)

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13
Q

Phase angle

A

Position of the pressure change as it moves through a cycle
Each complete cycle can be divided into 360 deg
The specific position of a pressure change is its phase angle
Especially useful in sound localization

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14
Q

Complex tones

A

Made up of several simple tones

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15
Q

Fourier analysis

A

How it is possible to identify the component sine waves of a complex sound

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16
Q

Fundamental

A

Lowest frequency in complex sound

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17
Q

How can a complex sound be described?

A

In terms of the frequency and intensity
Two dimensions define sound quality

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18
Q

Harmonics
AKA?

A

Other frequencies that are multiples of the fundamental
Undertones

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19
Q

Psychological aspect that underlies sound quality

A

Timbre

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20
Q

Why should we care about the properties of the auditory stimulus?

A

It’s all about understanding how we an hear to understand what is happening when we cannot hear!

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21
Q

Main classifications of the structures involved in hearing

A

Outer ear
Middle ear
Inner ear

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22
Q

3 structures in the outer ear

A

Pinna
Auditory canal
Eardrum

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23
Q

Pinna role

A

Some amplification; role in sound localization

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24
Q

Auditory canal

A

Keep dirt away from the eardrum (cerumen)
Amplification –> maximum 10dB for a 3000 Hz sound

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25
Eardrum AKA?
Vibrates in response to sounds Most important structure in the outer ear Tympanic membrane
26
Structures in the middle ear
The ossicles - malleus (hammer), incus (anvil), stapes (stirrup) Eustachian tube
27
Role of the ossicles
Amplification to counter impedance mismatch Outer ear: Sounds travel through air Inner ear: Sounds travel through water Change in medium creates resistance
28
In what 3 ways is the auditory system equipped to solve the impedance mismatch problem? What is the impact of the combination of these three factors?
The tympanic membrane is much larger than the region where the stapes meets the oval window The three ossicles act as a lever The eardrum is shaped like a cone, making its response more efficient Results in an increase by a factor of more than 20 dB in magnitude of the sound wave
29
Eustachian tube claim to fame
Helps equalize the pressure in the auditory system
30
Structures in the inner ear
Semi-circular canal Cochlea
31
Semi-circular canal purpose
Involved in our sense of balance, not hearing
32
Structures outside of the cochlea
Oval window Round willow
33
Oval window
Where the vibration from the stapes arrives
34
Round window
Where the vibration from the stapes dissipates after travelling through the cochlea
35
3 main classes (and counts) of structures inside the cochlea
Three canals Three membranes One organ
36
Three canals inside the cochlea
Vestibular canal Middle canal Tympanic canal - helicotrema links vestibular and tympanic
37
Three membranes inside the cochlea
Reissner's membrane Tectorial membrane Basilar membrane
38
Organ inside the cochlea
Organ of Corti
39
What kind of movement happens in the basilar membrane?
Travelling wave
40
What structure in the organ of corti can get damaged if exposed to loud songs for long periods of time?
Outer hair cells
41
Why should we care about the structures in the auditory apparatus?
Again, it's all about understanding how we can hear to understand what is happening when we cannot hear!
42
What is transduction in general?
Transformation of physical energy to neural impulses Neural code for physical stimuli
43
What is transduction in hearing?
Transforming sounds into neural impulses
44
Explain some of the structures involved in transduction in hearing and their locations
Hair cell contains several rows of stereocilia Inner hair cells stereocilia are freefloating Longer stereocilia in the outer hair cells are embedded in the tectorial membrane (can push or pull) Shorter stereocilia are not embedded in the tectorial membrane Stereocilia are linked to each outer by a fine strand (tip links)
45
Broadly, where does transduction take place? How does displacement occur?
In the hair cells Movements on (vibration of) basilar membrane produce displacement of stereocilia
46
What 2 phases are there in stereocilia and basilar membrane displacement? What force causes this?
Upward phase Downward phase Shear force
47
How does depolarization occur in transduction?
When the stereocilia are displaced toward the inner part of the cochlea (up), the hair cells become depolarized (excites firing of bipolar cells) When the stereocilia are displaced toward the outer part of the cochlea (down), the hair cells become hyperpolarized (inhibits firing of bipolar cells)
48
Brief summary of transduction (sum it all up)
Transduction takes place in the hair cells Through hyperpolarization and depolarization, the pattern of neural impulse reproduces the shape of the sound wave
49
What is a side effect of how transduction takes place?
The code for loudness and pitch perception
50
Code for loudness
The membrane vibrates more for loud sounds than for soft sounds More hair cells are affected This means more neural activity The amount of neural activity provides the code for sound amplitude
51
For the code of pitch, what two principles are involved?
Place principle Volley principle
52
For the code for pitch, what properties of the basilar membrane are crucial?
Stapes end: narrow and stiff Helicotrema end: wide and flexible
53
For the code for pitch, how do the frequency sizes interact with the basilar membrane? What principle makes use of this?
High frequencies reach their maximum at the stapes end of the basilar membrane Low frequencies reach their maximum near the helicotrema end Place principle
54
Place principle
The place (or location) on the basilar membrane where the sound vibration reaches its peak defines the frequency of the sound for the auditory system Location code for pitch
55
Code for pitch: Place principle
Complex tones are made up of a fundamental and several harmonics For complex tones, the place principle suggests that our auditory systems are designed to perform a Fourier analysis of complex tones
56
How does the volley principle complement the place principle?
Place principle cannot account for all hearing phenomena The missing fundamental illusion
57
Volley principle
Basilar membrane vibrate at the same frequency as the tone Vibration rate causes nerve fibres in the auditory nerve to fire at the same rate Basilar membrane vibrates at the same frequency as the tone causing nerve fibres in the auditory nerve to fire at the same rate
58
Basic problem that the volley principle addresses
Refractory period restricts the firing of nerve cells to 1000 times/sec Should not be able to code frequencies > 1000 Hz
59
Code for pitch: Volley principle
Groups of neurons work as a team to produce the required firing frequency A group of cells could represent a particular frequency by cooperating to produce a given firing rate in the auditory system
60
Downfall of volley principle
Above about 4000 Hz, the waves are moving too rapidly, and the neurons start firing out of tempo Volley principle cannot account for the perception of sounds above 4000 Hz
61
What does the volley principle account for?
The missing fundamental The fundamental is a complement of the vibration pattern, since it is a fraction of this pattern Fundamental vibrate in the firing rate of neurons coding the frequency
62
Do the volley principle and the place theory work together?
Yes
63
Claim to fame of the auditory cortex
Processes complex sounds
64
Auditory pathways and the auditory nerve
When a neural impulse leaves the cochlea, it travels along the auditory nerve Each cell in the auditory nerve seems to have a type of receptive field Using single-cell recording, researchers found that each neuron in the auditory nerve responds best to a particular frequency of sound
65
Tonotopic organization
Neurons sensitive to similar frequencies are found near one another
66
Auditory tuning curve AKA?
Graph showing the relation between the frequency of an auditory stimulus and the response of a specific neuron Frequency tuning curve
67
Auditory pathway connections
Contralateral connections stronger than ipsilateral connections
68
Dichotic presentations
Creates competition between ears Inhibits contralateral connection Used as screening procedure for brain surgeries
69
Auditory pathway relays
Tonotopic organization every step of the way Inferior colliculus: sound localization (where) Medial geniculate nucleus: sound identification (what)
70
Visual pathway relays
Superior colliculus: object localization Lateral geniculate nucleus: object identification
71
What % of cells respond selectively to complex sounds? Example? What do the other % do?
40% of cells respond selectively to complex sounds Frequency sweep detectors respond only to changes in frequency in a specific frequency and range 60% work together to code the presence of a stimulus
72
Name the most discussed kind of masking. What is crucial?
Simultaneous masking is all about basilar membrane interactions Frequency and intensity of the target and masker are crucial
73
What makes the best masker?
When it is of lower frequency than the target
74
Why should we care about the auditory system?
We now have an idea of what we should avoid to keep a healthy hearing apparatus

Survey of the Senses (13 decks)

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