Auditory system

Question 1

what are the 2 measures of sound

Answer 1

frequency and sound pressure level

Question 2

sound frequency

Answer 2

pitch; how rapidly wave cycles (crest to crest)

Question 3

sound pressure level

Answer 3

measures magnitude of pressure fluctuations; loudness of sound

Question 4

how is intensity of sound measures

Answer 4

amplitude of sound wave

Question 5

3 main cues to localize sounds

Answer 5

interaural time difference, interaural level difference and head-related transfer function

Question 6

interaural time difference

Answer 6

difference in time taken for a sound to reach each ear; incorporate from both ears (binaural cues)

Question 7

when is ITD greatest

Answer 7

when sound is 90 degrees (directly towards one ear)

Question 8

head-related transfer function

Answer 8

specifies how the body influences sound (body scatters) and provides vertical location cues based on changes in frequency spectrum

Question 9

interaural level difference

Answer 9

difference between sound pressure level at each ear

Question 10

sound shadow

Answer 10

obstacle casts by the head that lowers intensity of sound at ear furthest from stimuli

Question 11

when is ILD useful

Answer 11

high frequency sounds (ILD smaller is frequency decreases)

Question 12

what parts of the body influence how sound reaches inner ear; head related transfer function (HRTF)

Answer 12

pinna, head, torso

Question 13

spectral analysis

Answer 13

analyzing frequency content of a sound

Question 14

what cues are useful for low frequency sounds

Answer 14

interaural time difference (ITD)

Question 15

what cues are useful for high frequency sounds

Answer 15

interaural level difference (ILD)

Question 16

what are ILD and ITD useful for

Answer 16

localizing horizontal location of sound (incorporates info from both ears)

Question 17

what are the 3 bones in the middle ear

Answer 17

ossicles: malleus, incus, stapes

Question 18

how do sound waves enter the inner ear

Answer 18

tympanic membrane ->ossicle bones -> oval window

Question 19

cochlear fluids

Answer 19

-perilymph (low K+ conc) in scala tympani and scala vestibuli
-Endolymph (high K+ conc) in scala media

Question 20

basilar membrane

Answer 20

moves up and down with sound via fluid movement

Question 21

inner hair cells

Answer 21

transmit information to the brain; connected to basilar membrane

Question 22

outer hair cells

Answer 22

amplify movement of basilar membrane; connected to tectorial membrane

Question 23

tectorial membrane

Answer 23

membrane attached to tip of tallest stereocilia in outer hair cells; helps with hearing by stimulating hair cells and supporting traveling wave

Question 24

base of cochlea

Answer 24

narrow and stiff

Question 25

apex of cochlea

Answer 25

wide and floppy

Question 26

what part of the cochlea moves for high frequency sounds

Answer 26

base

Question 27

what part of the cochlea moves for low frequency sounds

Answer 27

apex

Question 28

how many rows of inner and outer hair cells are in the ear

Answer 28

1 row of inner hair cells and 3 rows of outer hair cells

Question 29

kinocilium

Answer 29

tallest hair in hair bundle

Question 30

hair bundle

Answer 30

slanted bundle of stereocilia on hair cell

Question 31

when do hair cells depolarize

Answer 31

stereocilia deflect towards kinocilium

Question 32

when do hair cells hyperpolarize

Answer 32

stereocilia deflect away from kinocilium

Question 33

hair cell action potential mechanism

Answer 33

K+ increase depolarizes hair cell -> Ca2+ channels open -> glutamate response -> action potential to ganglion cells -> auditory nerve

Question 34

characteristic frequency/ best frequency

Answer 34

the frequency where the spiral ganglion cells responds to the most

Question 35

auditory nerve response: phase locking

Answer 35

neurons fire action potentials at a particular phase of sound wave which provides frequency information

Question 36

when does phase locking occur

Answer 36

at low frequencies (under 4,000 Hz)

Question 37

how is frequency information obtained for high frequencies (over 4,000 Hz)

Answer 37

tonotopic arrangement of auditory nerve fibers

Question 38

superior olive

Answer 38

earliest area sensitive to binaural cues

Question 39

where are ITD encoded

Answer 39

medial superior olive

Question 40

where are ILD encoded

Answer 40

lateral superior olive

Question 41

mechanism for ILD and ITD encoding in superior olive

Answer 41

activity in 1 ear initiates activity and sends info to superior olive, initiates activity in right ear, signals for both years meet at a neuron

Question 42

pathway from inner ear to auditory cortex

Answer 42

cochlea, spiral ganglion, auditory nerve, dorsal/ventral cochlear nucleus ventral cochlear nucleus(timing info) -> superior olive dorsal cochlear nucleus (HRTF) -> inferior colliculus MGN in thalamus -> auditory cortex

Question 43

where is the auditory cortex in humans

Answer 43

dorsal and lateral superior temporal gyrus

Question 44

what are the 3 subsections of the auditory cortex

Answer 44

core, belt, and parabelt

Question 45

what are the 3 tonotopic areas in the core of the auditory cortex

Answer 45

primary auditory cortex (A1), rostral field (R), rostral temporal field (RT)

Question 46

how is the core of the auditory cortex organized

Answer 46

tonotopically; orderly arrangement of neurons in terms of characteristic frequency/ best frequency

Question 47

tonotopic organization of belt and parabelt

Answer 47

belt: some tonotopic organization parabelt: not well organized (tonotopically)

Question 48

what does the parabelt region interpret

Answer 48

speech patterns (not tonotopically organized)

Question 49

subsections of auditory cortex hierarchy (low -> high)

Answer 49

core, belt, parabelt

Question 50

harmonics

Answer 50

multiple frequencies that constitute sound

Question 51

harmonic complex tones (HCT)

Answer 51

sound composed of multiple frequencies where each frequency is an integer multiple of a fundamental frequency (F0)

Question 52

what class of sound does the core respond best to

Answer 52

pure tones (single frequency)

Question 53

what class of sound does the belt respond best to

Answer 53

band-passed noise (intermediate complexity)

Question 54

what class of sound does the parabelt respond best to

Answer 54

species specific vocalization/ speech and vowel sounds (complex sounds)

Question 55

ventral pathway from auditory information

Answer 55

what the sound is; core -> belt regions -> inferior frontal cortex

Question 56

dorsal pathway for auditory information

Answer 56

where sound is and how to interact with it; auditory cortex -> parietal cortex (intraparietal lobule) -> frontal cortex (premotor cortex)

Question 57

how does change from non behaviorally relevant info to behaviorally relevant info impact action potential

Answer 57

increase in neuron firing

Question 58

how does change from one behaviorally relevant info to another behaviorally relevant info impact action potential

Answer 58

no significant change in action potentials

Question 59

how does the ventral pathway assign sounds categories

Answer 59

different neurons respond to different sounds/ phonemes *morphed word monkey study

Question 60

where in the brain processes phonemes

Answer 60

superior temporal gyrus *different neurons respond to different phonemes

Question 61

what speech does posterior superior temporal gyrus represent

Answer 61

fast varying speech sounds (phonemes)

Question 62

what speech does antierior superior temporal gyrus represent

Answer 62

slow varying speech sounds (ex. rhythm of speech)

Question 63

what speech does middle superior temporal gyrus represent

Answer 63

medial time scale sounds (ex. syllables)