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PSYC 367 > L5-L7 > Flashcards

L5-L7 Flashcards

1
Q

How is sound produced?

A

physical vibration of objects (a purely mechanical phenomena)

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2
Q

Compression vs rarefaction

A

air molecules bunch together (high air pressure); air molecules spread apart (low air pressure)

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3
Q

Frequency

A

rate of fluctuation of sound pressure measured in cycles/second or Hertz (Hz)

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4
Q

Phase

A

part of the cycle the sound pressure wave has reached at a given point in time; measured in degrees until 360°; often used to compare the timing of 2 sound waves

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5
Q

Amplitude

A

maximum pressure change of wave above normal atmospheric pressure that determines sound intensity

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6
Q

Pure tones

A

represented by single sine wave and produced by a tuning fork, wherein sound pressure level corresponds to loudness and frequency corresponds to pitch

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7
Q

Fourier’s theorem

A

most sounds are complex and can be described as a set of sine waves

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8
Q

Fourier analysis

A

mathematical procedure for separating a complex pattern into component sine waves that vary over time (hearing) and space (vision)

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9
Q

Fundamental frequency

A

lowest sine-wave frequency in a complex sound that usually determines perceived pitch

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10
Q

Harmonics

A

higher frequency sine-wave components; integer multiples of fundamental frequency

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11
Q

What do differences in frequency and amplitude in harmonics determine?

A

the psychological attribute of quality or timbre (i.e. explains why instruments sound different when playing the same note)

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12
Q

Function of the shape of the pinna

A

helps with sound localization

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13
Q

Function of the length and shape of the ear canal

A

enhances sounds 2000-6000 Hz (range of frequency where humans are most sensitive)

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14
Q

Function of the middle ear

A

impedance matching and protecting the inner ear from potentially harmful loud sounds through acoustic reflex

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15
Q

Impedance matching

A

middle ear amplifies sound energy to reduce loss due reflection at the oval window (air/fluid boundary)

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16
Q

Acoustic reflex

A

tensor tympani and stapedius muscles contract to reduce the magnitude of the auditory signal transmitted to the inner ear, in response to prolonged sounds

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17
Q

Function of the eustachian tube

A

equalizes air pressure between the middle and outer ear

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18
Q

3 canals in the inner ear

A

vestibular canal (scala vestibuli), middle canal (cochlear duct or scala media), tympanic canal (scala tympani)

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19
Q

What do the vestibular and tympanic canals contain?

A

fluid called perilymph

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20
Q

What does the middle canal contain?

A

fluid called endolymph and organ of corti that contains auditory receptors (where mechanical energy is transduced into neural signals)

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21
Q

Function of the tunnel of corti

A

locating 2 different hair cells: 1 row of 3500 inner hair cells on one side and 3 rows of ~10500 outer hair cells on the other

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22
Q

Location of inner hair cells vs outer hair cells in the cochlea

A

single row of stereocilia that rests against the tectorial membrane (gelatinous roof of the organ of corti); V-shape arrangement of stereocilia with the tallest embedded in the tectorial membrane

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23
Q

Function of inner hair cells

A

act as sensory receptors that convey information about sound to the brain

have no axons but release neurotransmitters at the synapse with afferent fibers

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24
Q

Function of outer hair cells

A

modulate sensitivity and frequency-tuning of cochlear partition

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25
Q

General function of hair cells (stereocilia)

A

transduction

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26
Q

How does movement of the basilar membrane cause transduction?

A

when it moves up and down, hair cells bend back and forth against the tectorial membrane, causing neurotransmitter release into the synapse with the dendrites of the auditory nerve fibers

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27
Q

What comprises the auditory nerve (part of vestibulocochlear nerve)?

also called cochlear nerve

A

axons of the auditory nerve fibers

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28
Q

2 kinds of auditory nerve fibers

A

afferent fibers and efferent fibers

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29
Q

Afferent fibers

A

carry sensory information to the CNS and fires action potentials; 90% is connected to the inner hair cells and 10% is connected to the outer hair cells

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30
Q

Efferent fibers

A

carry information from the CNS to the inner ear and comprises of most neurons synapsing with the outer hair cells

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31
Q

Graded potential vs action potential

A

slow change in membrane voltage that varies in size (not all-or-nothing) and occurs in hair cells; rapid depolarization that occurs in auditory nerve fibers

32
Q

Place code for sound frequency

A

different places on the cochlea are tuned to different frequencies; sound frequency is converted into position on the basilar membrane and sound wave peaks at different places for each frequency of sound

33
Q

Where do high frequency vs low frequency sounds peak on the basilar membrane?

A

high frequency peaks closer to the oval window (stiff and narrow membrane near cochlear base); low frequency peaks closer to the helicotrema (wide and loose membrane near cochlear apex) and more of the basilar membrane is activated

34
Q

Black curves on the sound wave of a pure tone

A

represents the basilar membrane response to a pure tone at 2 instants in time

35
Q

Red curve on the sound wave of a pure tone

A

envelope of all possible travelling waves for the pure tone that shows the maximum amplitude for each position

36
Q

Cochlear amplifier

A

an active process is sharpening and amplifying the frequency response of the basilar membrane (peak is higher and narrower in the living ear) compared to the passive process based on its physical properties

37
Q

What causes the active process in the basilar membrane response?

A

electromotility of the outer hair cells, which produces otoacoustic emissions as a byproduct

38
Q

Electromotility

A

ability of outer hair cells to lengthen and contract in response to changes in electric potential

39
Q

3 changes that occur in outer hair cells during electromotility

A

(1) depolarization causes contraction; (2) hyperpolarization causes elongation; (3) voltage-sensitive protein (prestin) changes shape

40
Q

Otoacoustic emissions

A

sounds emitted by healthy ears

41
Q

2 kinds of otoacoustic emissions

A

evoked emissions and spontaneous emissions

42
Q

Evoked emissions

A

occurs in response to auditory stimulation and depends on the frequency of the stimulating sound; used clinically as a quick indicator of inner ear damage

43
Q

Spontaneous emissions

A

occurs without stimulation and very weak (less than 20 dB, 100-2000 Hz); taken as evidence for outer hair cell involvement in the cochlear amplifier

44
Q

How do you reduce spontaneous emissions?

A

aspirin (reduces activity of the outer hair cells but not the inner)

45
Q

Characteristic frequency

A

frequency that increases the firing rate of the afferent fiber at the lowest intensity

lowest absolute threshold at lowest point of threshold tuning = high sensitivity

46
Q

Contribution of outer hair cells to afferent fibers (which synapse with inner hair cells)

A

improves their sensitivity (threshold intensity for firing above spontaneous rate) and frequency selectivity (sharpness of tuning curve)

47
Q

Two-tone suppression

A

firing rate of AN fiber to its characteristic frequency for a test tone decreases when a suppressor tone of similar frequency is presented simultaneously

48
Q

When are suppression effects on an AN fiber pronounced?

A

when the second (suppressor) tone has a lower frequency than the first (test) tone

49
Q

Isointensity curves

A

show the average firing rate of the neuron in response to different intensities over the same frequency range

50
Q

Rate saturation

A

point at which an afferent fiber is firing as fast as possible and further stimulation can’t increase firing rate (i.e. loss of frequency tuning at higher intensities)

51
Q

What is the frequency at which the basilar membrane has poor frequency discrimination?

A

< 500 Hz where the entire basilar membrane is involved in its response and there is no peak

52
Q

Phase-locking

A

AN fibers tend to fire at a particular point (or phase) in the cycle of a sound wave, which provides a temporal code for frequencies below 1000 Hz

53
Q

Volley principle

A

combined firing of a group of afferent fibers matches the frequency of an incoming sound (1000-4000 Hz) to provide a temporal code for frequency

afferent fiber can’t fire on every cycle at frequencies above 1000 Hz

54
Q

3 aspects of afferent fiber firing that code sound frequency

A

(1) timing of firing for frequencies below 500 Hz; (2) place of maximum firing for frequencies above 4000 Hz; (3) temporal and place information at frequencies between 500 and 4000 Hz

55
Q

How does pattern of firing code for sound intensity?

A

more auditory nerve fibers of each type (low, mid, and high spontaneous) from a particular region of the basilar membrane fire as sound intensity increases

56
Q

Sound intensity threshold of low spontaneous fibers

A

high threshold (above 60 dB) to reach maximum firing rate (above spontaneous level)

57
Q

Sound intensity threshold of high spontaneous fibers

A

low threshold (below 60 dB) to reach the maximum firing rate (above the spontaneous level)

58
Q

How does pattern of firing code for a frequency?

A

auditory nerve fibers from different regions of the basilar membrane fire when intensity is constant but frequency is changed

59
Q

Monaural neurons vs binaural neurons

A

receives input from only one ear; receives input from both ears

60
Q

Threshold tuning curves

A

defines the absolute threshold intensity of individual auditory nerve fibers as a function of frequency

i.e. the lowest intensity necessary for neuron to fire above its spontaneous rate at each frequency

61
Q

3 subdivisions of the cochlear nucleus

A

dorsal, posteroventral, anteroventral

62
Q

Dorsal cochlear nucleus

A

axons of neurons that project to the superior olive (but don’t synapse) cross over to the opposite side of the brain

63
Q

Posteroventral cochlear nucleus

A

axons synapse in the contralateral superior olive

64
Q

Anteroventral cochlear nucleus

A

axons synapse in the contralateral or ipsilateral superior olive

65
Q

3 functions of olivocochlear bundle

A

efferent fibers that protect the inner ear from loud sounds; suppress continuous background noise for easier sound detection; help with sound localization

66
Q

Where do fibers from the medial superior olive in the olivocochlear bundle project to?

A

outer hair cells (mainly contralateral), which reduces its electromotility and otoacoustic emissions

67
Q

Where do fibers from the lateral superior olive in the olivocochlear bundle project to?

A

dendrites of type I afferents (mainly ipsilateral)

68
Q

3 subparts of the auditory core region

A

primary auditory cortex (A1), rostral core, and rostrotemporal core

69
Q

2 belt regions surrounding A1

A

belt and parabelt

70
Q

Tonotopic map

A

neurons that respond to different frequencies are organized anatomically in order of frequency to which they are most sensitive

71
Q

Where are tonotopic maps found in the auditory system?

A

all structures (cochlear nucleus, superior olives, olivocochlear bundles, inferior colliculus, medial geniculate)

72
Q

Tonotopic map in the belt

A

cruder and incomplete; neurons respond to complex sounds

belt has 6 subregions!

73
Q

Tonotopic map in the parabelt

A

some tonotopy; neurons respond to speech sounds; involved in multi-sensory integration

74
Q

“Where” pathway in the auditory cortex

A

posterior parabelt to posterior parietal cortex to dorsolateral prefrontal cortex; more activated by detecting a location

75
Q

“What” pathway in the auditory cortex

A

anterior parabelt to orbitofrontal cortex; more activated by recognizing pitch

PSYC 367 (7 decks)

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