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Anatomy and Physiology > Neural Coding / Sound Localization > Flashcards

Neural Coding / Sound Localization Flashcards

Coding of Sound Features / Localization of Sound in Space

1
Q

review: the sharpening mechanism provided by the ___________ (OHCs) to enhance the spatial resolution (frequency resolving power) of the basilar membrane

A

cochlear amplifier

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2
Q

the hearing range implies that each individual frequency is “best represented” by a patch of BM = to about ____ mm or about ____ um, which is at best _____ individual hair cells

A

0.02 mm; 20 um, 9-12 individual hair cells

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3
Q

manner in which info about a stimulus (sound or ant other sensory modality) is represented by neuronal activity

A

neural code

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4
Q

specific set of input patterns to which a neuron will respond
- think low level vs high level
- think broad vs narrow
(all diff types of sensory info)

A

receptive field

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5
Q

range of a stimulus parameter (intensity, freq, direction, etc.) which is reflected by neuronal activity
- neuronal activity. helpful for identification of stimulus parameter

A

dynamic range

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6
Q

auditory neurons response to stimulus intensity typically increase firing rate through the dynamic range of _____ dB but the response becomes saturated at that point

A

20-50 dB

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7
Q

what characterizes individual neuron?

A

neuron tuning curve

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8
Q

stimulate neurons @ lowest stimulus level
- least amount of energy need to stimulate

A

characteristic frequency

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9
Q

different characteristic frequencies have different what? (3)

A

1) different nerve fibers
2) different thresholds
3) different bandwidths

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10
Q

the characteristic frequency of a given fiber is roughly the same as the __________ of part of the BM that it is attached to

A

resonant frequency

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11
Q

minimal stimulus needed to produce a response at that charactersitc frequency is the ___________

A

threshold

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12
Q

_______ affects the neuron curve

A

ototoxicity

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13
Q

how can ototoxicity affect the neuron tuning curve?
(3 ways)

A

1) elevated threshold
2) widened bandwidth
3) shift of characteristic frequency toward lower frequency

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14
Q

characteristic frequency is directly related to the ___________ on BM

A

location

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15
Q

increased frequency means it is ________ to basal end of cochlear

A

closer

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16
Q

certain cells respond to certain types of stimulus
- freq dependent (auditory) or movement dependent (visual)
- most basic
- if this neuron is firing, this is what it means

A

labeled line code

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17
Q

express or relay info about the intensity of a stimulus

A

rate code

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18
Q

rate of firing of a given neuron is dependent on the _________

A

stimulus intensity

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19
Q

known as DR, auditory neuron rate increases through range of __________ and then __________

A

20-50 dB and saturates

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20
Q

aspect of stimulus = reflected by _________

A

firing rate, which carrys info

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21
Q

neuronal activity (firing) locked to the periodicity of the stimulus

A

temporal code

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22
Q

how can temporal code be useful?

A

useful for stimulus parameters that can be designated by that periodicity (frequency)

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23
Q

what are the limitations of the neural coding strategies?

A

they limit the firing limit of action potential mandates

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24
Q

different nerve fibers elicit different sensations by virtue of their central connections on BM

A

PLACE THEORY

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25
Q

acoustic info is carried by the rate or frequency of the discharge of a neuron

A

TEMPORAL THEORY

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26
Q

firing rate can be tuned to the frequency of certain stimuli

A

phase locking

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27
Q

______ theory can be seen in cochlear implants (benefits and limitations)

A

place

28
Q

phase locked neurons fire to a ________ in sine wave cycle

A

specific point

29
Q

phase locking works up for frequencies up to about _____ Hz

A

1000 Hz

30
Q

group of neurons/hair cells that can work collectively to continue this place locking by sharing the responsibility of representing each part of the stimulus

A

volley principle

31
Q

illustration of volley principle

A
32
Q

which theory best accommodates the needs of the auditory system?

A

both place and temporal theory

33
Q

widening of cochlear tuning with increasing intensity improves reproduction of the _________ pattern while degrading the spatial patterm

A

temporal

34
Q

sharp tuning observed at LOWER frequencies facilitates _________

A

spatial resolution
- at the expense of temporal resolution

35
Q

what is one of the most critical functions of the auditory system?

A

localization of sound in space

36
Q

why is localization so important?

A

auditory signal recognizes - 13 ms as opposed to 1 ms
- time of arrival is different (shorter)
- system works with high accuracy & reproductivity (fidelity)

37
Q

what two types of information does the central auditory pathways derive about localization

A

1) ITD (interaural time difference)
2) ILD (interaural level difference)

38
Q

different between arrival times of acoustic stimulus at both ears

A

ITD

39
Q

difference between stimulus amplitudes (intensities) at both ears

A

ILD

40
Q

a change of 1-2 degrees in the location of a stimulus corresponds to an ITD of about ______ microseconds

A

13 microseconds

41
Q

ITD works better with _____ frequencies

A

low frequencies
(one ear first then to second ear)

42
Q

ILD works better with _______ frequencies

A

high frequencies
(head shadow effect - less intensity)

43
Q

degree of exactness with which something is copied or reproduced

A

fidelity

44
Q

______ is useful when sound waves are large enough to wrap around head and avoid shadowing
- wavelength of 500 Hz
- phase info (most useful below <1.5kHz

A

ITD

45
Q

caused by shadowing of sound stimuli by structures of the head
- cues exist only for frequencies > 500 Hz and reliable for frequencies above 3kHz

A

ILD

46
Q

________ differences between L and R ears are most effective for localization for higher frequency stimuli

A

ILD

47
Q

_____ consists of stacks of neurons, each receiving inputs from both ears

A

MSO

48
Q

where is MSO on the auditory pathway

A

SOC

49
Q

MSO system detects which neuron receives _______ signals from both sides and determines localization based on that info

A

coincident (same time)

50
Q

MSO works best for localizing ______ frequencies

A

lower

51
Q

illustration for understanding MSO

A

which neurons get sent to both ears at same time

52
Q

MSO and ITD illustration

A
53
Q

________ consists of stacks of neurons, each receiving bilateral inputs, but the contra input has passed through the MNTB to become a inhibitory signal

A

LSO

54
Q

LSO amplifies the level difference and allows even subtle ILD to be transformed into an ___________ response

A

an all-or-nothing

55
Q

LSO is better with ______ frequencies

A

higher

56
Q

ascending pathways: neuronal activity at any level, info can be extracted, may be modified by _________ feedback circuits

A

descending

57
Q

what specializations are unique among sensory neural networks and allow for signal precision or fidelity (2)

A

1) ribbon synapses
2) giant terminals
- endbulbs
- calyces of Held

58
Q

specialized transport & timing system for synaptic vesicle release designed for synapses that require a wide dynamic range and accurate sustained release

A

ribbon synapse

59
Q

what can you think of the ribbon synapse as?

A

Ferris Wheel
- constantly tuning to provide accurate delivery of vesicles (NT) to BM
(time release & ongoing release)

60
Q

where are ribbon synapses found?

A

in auditory system and portions of light system

61
Q

ribbon is a very dense structure surround by ___________

A

synaptic vesicles

62
Q

what do the endbulbs of Held consist of? (2)

A

staining neurons such as:
1) axosomatic terminals
2) spoon-shaped with filopodia

63
Q

what is the LARGEST nerve terminal in CNS

A

Calyces of Held

64
Q

the 2 terminals associated with Calyces of Held are associated with what pathways?

A

pathways used to localize in space

65
Q

what do calyces of held arise from?

A

AVCN projecting to (synapsing on) the contra medial nucleus of trapezoid body (MNTB)

66
Q

neither cue works well
- human localization in this range tends to be relatively poor as a result

A

around 2,000 Hz

67
Q

____________ promote fidelity or accuracy of stimulus reproduction/analysis by the auditory system.

A

Synaptic specializations

Anatomy and Physiology (17 decks)

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