Auditory Nervous System

Question 1

auditory nerve

Answer 1

a direct synaptic connection between the hair cells of the cochlea and the cochlear nucleus

Question 2

Type I fibers

Answer 2

90-95% of spiral ganglion cells
connected to IHCs
many-to-one (20 fibers to one IHC in humans)

Question 3

Type II fibers

Answer 3

5-10% of spiral ganglion cells
connected to OHCs
one-to-many (one fiber to 10 OHCs in humans)

Question 4

spontaneous firing

Answer 4

auditory neurons fire by themselves, even with no stimulation or sound

Question 5

higher spontaneous firing is associated with ________ threshold

Answer 5

lower

Question 6

low firing rate

Answer 6

rate is less than 1/2 per second
within 2 seconds, rate is fired
hardest to excite

Question 7

tuning curve

Answer 7

shows amplitude displacement of BM
frequency selective
4 curves at 4 levels
wave starts at stapes then travels across the BM

Question 8

high firing rate

Answer 8

rate is higher than 18 times per second

easiest to get excited

Question 9

frequency selectivity

Answer 9

the action potential for each neuron has its own tuning curve and CF
each point on the BM has a “favorite” frequency that the BM responds to the best

Question 10

tonotopic organization

Answer 10

high frequency sounds stimulate the base of the cochlea, and low frequency sounds stimulate the apex

Question 11

intensity resolution

Answer 11

nonlinearity at CF and linearity at non-CF

Question 12

saturation level

Answer 12

where the firing level will not change

Question 13

dynamic range

Answer 13

20-50 dB

saturation level - threshold

Question 14

phase locking

Answer 14

temporal pattern of the neural firings

Question 15

frequency limit of phase locking

Answer 15

up to about 4-5 kHz

Question 16

rule of phase locking

Answer 16

neural firing follows the phase of the 1st firing (does not mean neuron will fire every cycle)

Question 17

4 nuclei (levels) of the auditory brainstem

Answer 17

cochlear nuclei (CN)
superior olivary complex (SOC)
nuclei of lateral lemniscus (NLL)
inferior colliculus (IC)

Question 18

cochlear nuclei (CN)

Answer 18

has complex response pattern

1st central auditory station –> receives info from auditory neurons

Question 19

superior olivary complex (SOC)

Answer 19

receives bilateral (from both sides) inputs
critical for sound localization

Question 20

nuclei of lateral lemniscus (NLL)

Answer 20

relay station of auditory brainstem

Question 21

inferior colliculus (IC)

Answer 21

combines the analysis of complex sound
integration center
does all functions that lower levels do

Question 22

what makes up the auditory forebrain?

Answer 22

medial geniculate body (MGB)

auditory cortex

Question 23

medical geniculate body (MGB)

Answer 23

processes and relays specific detailed auditory information to the auditory cortex

Question 24

auditory cortex

Answer 24

made of 2 parts: primary auditory cortex and secondary auditory cortex
final destination of sound