1.
aphasia: deficits in speech perception
2.
bilateral lesions lead to...: can't discriminate between tonal patterns
3.
define place coding better:: happens when fiber is hooke dup to cells in the cochlea sensitive only to one given frequency
4.
describe endolymph: in the scala media-high potassium. potential = 80 mV
5.
describe oval and round windows:: two membrane covered openings in the bone surrounding the cochlea
-permit displacement of perilymph in response to stapes motion
6.
describe PABI: -used for type 2 neurofibromotosis
-not as good as cochlear implant
7.
describe perilymph: in scala tympani and vestibuli. low potassium. potential = 0mV
8.
describe the cell columns: perpedicular to pial surface-either summation or suppression columns
-summation-biaural input
-suppression- monoaural input
9.
describe the main auditory cortex?: -organized into layers and into columns of cells
-layers differ in cytoarchitecture. fibers from geniculate terminate in layer 4
-info moves from Broadmans Area 41-->42-->39-->22 (wernike's)--> 45 (broca's)
10.
describe the tectorial membrane/basilar membrane role: -resting position it is lying over the hair cells and not moving
-sound vibration comes in and causes the basilar membrane to move. it enters upward phase and hair cells point toward the apex due to shear force (tips of hair cells embedded in the tectorial membrane)
-then enters downward phase, causing the hair cells to point in the other direction
11.
describe what happens at the cellular level when the basilar membrane is displaced:: -movement of the cilia induces generator potential in the hair cells
-there is a linking filament between the hair cells individual hairs--this is a mechanical gate of the potassium channels there. when you go toward the apex (tall point) the filament is stretched, opening the potassium channels-->depolarization
-when you go the other way the filament is squished, so channels don't open
12.
how is sound localized?: -in the superior olivary nucleus
-based on timing of when info comes in from each side-->which one reaches the cochlear nucleus first?
in the superior olive-one side signals before the other until you get to neuron 3 and they reach at the same time. summation gives you the action potential
-stronger stimulus on left side would excite the left LSO, while inhibiting the right LSO via MNTB interneuron
go over photo in ppt
13.
how to fix hearing deficits?: audiometry (test for deficits)
auditory evoked potentials (test for deficits)
cochlear implant (cochlear stimulator)
penetrating electrode auditory brainsetm implant (PABI)
-otoacoustic emissions (infant screening)
14.
left hemisphere is better at...: verbal sound discrimination
15.
lesions on one side...: damage ability to localize sound, but can still hear tones
16.
meniere's disease: increased pressure in scala media
17.
otosclerosis: middle ear bone fusion
18.
pathway for auditory info?: -first order neurons--> cochlear nuclei-->superior olive and trapezoid body (medial/lateral superior olive)-->inferior colliculus-->medial geniculate-->auditory cortex
note that these are tonotopically organized
19.
potential of inner hair cells?: -45mV
20.
presbycusis: loss of high frequency cells due to aging
21.
right hemisphere is better at...: music discrimination
22.
what are the hearing deficits?: conduction deafness
sensorineural deafness
presbycusis
tinnitis
hyperacusis
aphasia
23.
what are the properties of sound?: -frequency
-amplitude
-temporal
-spatial
24.
what are the three routes of conduction?: -air (permits low level hearing in people whose stapes is ossified to oval window, if a small opening is drilled in the horizontal semicircular canal)
-osseus
-ossicular
25.
what are the two types of nerve endings at the ends of hair cells?: 1) efferent fibers-from superior olive via olivocochlear bundle. these contain synaptic vesicles
2) Afferent fibers: 90% from inner hair cells. these have tuning curves?
26.
what are the types of secondary receptors? where are they?: inner hair cells and outer hair cells
-outer cells are embedded at their case in the stiff reticular lamina with cilia embedded in tectorial membrane
-3500 inner hair cells
-20,000 outer hair cells (amplifiers of sound)
27.
what causes basilar membrane displacement?: -waves in the endolymph
28.
what damages the hair cells?: -furosemide
-aminoglycosides
-loud noise
29.
what divides the cochlea? what are the compartments called: divided into three compartments by reissners membrane and a basilar membrane
1) scala vestibuli
2) scala media
3) scala tympani
M and T divided by basilar membrane
V and M divided by Reissners?
30.
what do MSO and LSO do?: -MSO responds to differences in arrival time
-LSO detects differences in intensity
31.
what does radial movement of the basilar membrane do?: -presses outer hair cells against the lamina and pulls on the INNER hair cells
32.
what is amplitude measured in?: decibels. threshold of human hearing is around 0 decibels.
-anything above 100 decibels damages hair cells and above 140 induces pain.
33.
what is cochlear amplification?: happens when potassium enters the hair cell, activating motor proteins and lengthening the hair cell. this further increases the bending of the basilar membrane, so amplifies the sound
34.
what is fourier analysis?: for our purposes: adding together individual sound waves to make combined waves
35.
what is frequency related to?: -intensity-as frequency goes up, intensity (amplitude) goes down to a certain point (threshold of hearing) and then it starts to go back up after that
36.
what is impedence matching?: -conduction of sound waves into the cochlea thru the ossicles (from ear drum to oval window)
37.
what is sound?: a wave of alternating bands of low/high pressure in air--vibration
38.
what is the most frequent sensory problem?: hearing disorders
39.
what is volley coding?: occurs for sounds below 4000 cos. one fiber is phase locked to stimulus frequency-->it will fire at phase peak or trough, but not every peak/trough?
40.
what participates in protective reflexes:: -middle ear muscles-protect from loud sounds (tympanic/attenuation reflex)
-controlled by auditory efferent fibers (40-160 ms lag time)
-muscles may be active during speech to reduce intensity of voice and protect vs low frequency noise
41.
what protects vs sudden pressure changes?: -eustacian tube
42.
what will increase decibels?: -increase in intensity of sound and pressure of sound
43.
where are auditory receptor cells located?: on the organ of corti in the cochlea
44.
where do low frequency waves distort the basilar membrane? high frequency?: -maximally at the apex of the cochlea
-high frequency is at the base of the cochlea
this is called place coding. my assumption is that this is related to frequency tuning also, because fibers will fire differently depending on the frequency of the tone, probably because of the way the basilar membrane moves
45.
where does most sound input come from?: the inner hair cells
46.
where is the organ of corti?: resting on the basal membrane in the scala media
47.
where is the tectorial membrane?: -sticking out into the scala media over top the organ of corti and the hair cells
48.
who came up with the resonance wave theory?: herman von helmholz
49.
who came up with the traveling wave theory?: georg von bekesy (this is the commonly accepted theory now)
50.
why are tuning curves sharper at higher levels?: afferent/lateral inhibition
