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Cellular and Systems Neuroscience > Auditory Circuits > Flashcards

Auditory Circuits Flashcards

1
Q

what does the outer ear contain

A

pinna and ear canal
filters incoming sound and sends to eardrum

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2
Q

what does the middle ear contain

A

ossicles (air-filled)
impedance matching

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3
Q

what does the inner ear contain

A

cochlear
semi-circular canals
vestibular apparatus

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4
Q

3 types of scalae (fluid-filled cavities)

A

vestibuli , media, tympani

vestibuli and tympani contains perilymph
vestibuli and supporting cells control homeostasis

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5
Q

where are the IHCs and OHCs located

A

organ of corti (also contains basilar membrane)
inside cochlea

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6
Q

role of OHC and IHC

A

OHC - active amplification
IHC - signal tranduction

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7
Q

role of stereocilia

A

located on the apical surface
signal transduction in the cochlea
undergo sheer force
deflected to longest stereocillia

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8
Q

steps in signal transduction

A

mechanoelectrical transducer channels (MET) open
causes hair cell depolarisation
influx of K+ ions in hair cells
driven by electrochemical gradient of scala media
Ca2+ channels depolairsation
vesicles fuse to hair cell membrane
NT release

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9
Q

IHC membrane potential

A

follows low stimulus frequencies

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10
Q

OHC membrane potential

A

follows very high stimulus frequencies

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11
Q

what does the OHC contain

A

prestin (in membrane)
alters conformation and length

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12
Q

what is the basilar membrane

A

where the sensory epithelium sits

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13
Q

where does frequency tuning occur

A

in the auditory nerve
projections from spinal ganglion to cochlean brainstem

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14
Q

where does the ascending auditory pathway project

A

brainstem
midbrain(inferior colliculus)
thalamic nuclei
cortex

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15
Q

what is the ascending auditory pathway response

A

contains crossed and uncrossed projections
response change is higher up in the CAS
cortex has a sluggish response
stimulus specific adaptations and dynamic change in response
binaural response

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16
Q

where does the descending auditory pathway project

A

cortex
thalamus
MB
BS
cochlea

17
Q

what does the descending auditory pathway contain

A

complex crossed and uncrossed projections
corticofugal modulation (peripheral nuclei to cochlea) - alters hair cells and protects against excessive sound
olivocochlear feedback to OHC and protection against specific sound

18
Q

monaural cues

A

pinna transforms sounds into spectral notches
perception of elevation above/below plane and resolution of front/back ambiguity

19
Q

binaural cues

A

interaural time differences (ITDs)
interaural level differences (ILDs)
perception of azimuth (horizontal L/R plane)

20
Q

mammalian vs avian

A

-birds and reptiles have widened interaural distance due to acoustic coupling of L/R middle ear cavities
-avian have larger ITDs (max=200us) than mammals with equivalent head size

21
Q

ITDs

A

predominant binaural cue for low frequencies <2kHz
(wavelength > head diameter)
larger heads = more ITD detection
low frequencies diffract around the head

22
Q

human ITD discrimination

A

small changes - 1-2 degrees of angular location
threshold = 10us

23
Q

avian ITD

A

delay line arrangement - to give ITD sensitivity
map of auditory space in nuclear laminaris
EE cells in NL are coincidence detectors
temporal summation of EPSP inputs - excitation only

24
Q

steps in ITD

A

1) sound reaches L ear first
2) AP towards MSO
3) sound reaches R ear
4) AP from R ear towards MSO
5) APs converge on MSO neuron which responds strongly if arrival coincident

25
Q

mammalian ITD

A

ITD tuning in MSO not organised into space map
peak ITD function outside physiological range of ITDs
peak position cannot encode ITDs
maximum ITD occurs at midline

26
Q

ILDs

A

predominant cue for high frequencies >2kHz
(wavelength<head diameter)
easily reflected by head

27
Q

how are ITDs tuned

A

excitation
phase-locked inhibtion

28
Q

lateral superior olive LSO

A

LSO neurons has glycingeric inhibtion and glutamatergic excitation
de novo degeneration of ILD sensitivity in IC and ILD in IC (crossed and uncrossed pathways)

Cellular and Systems Neuroscience (21 decks)

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