Audition

Question 1

tympanic membrane

Answer 1

eardrum, vibrates with sound waves and transmits to bones in middle ear

Question 2

bones in middle ear

Answer 2

malleus, incus, stapes

stapes vibrates against membrane of cochlea

Question 3

cochlea

Answer 3

• part of inner ear
• filled with fluid
• snail-shaped

Question 4

organ of Corti

Answer 4

• receptive organ inside the cochlea

- consists of basilar membrane, hair cells, and tectorial membrane

Question 5

hair cells

Answer 5

• auditory receptor cells
• contain cilia between basilar membrane and tectorial membrane
• vibration causes these membranes to flex back and forth sending “waves” through the inner ear fluid causing cilia to bend (like kelp swaying). Bending in hair cells results in action potential in neurons going to cochlear nerve to auditory nerve (cranial nerve 8)

Question 6

basilar membrane

Answer 6

Tonotopic representation
- Different parts of basilar membrane respond to different sound frequencies (tones), low to high
Specific parts of the basilar membrane project to specific parts of the brain stem nuclei

Question 7

CNS, parts involved in audition

Answer 7

Auditory pathways are majority (75%) contralaterally mediated
- Auditory nerve to cochlear nuclei and superior olivary complex in medulla, where perception of sound location is processed
- From medulla to inferior colliculus
- to medial geniculate body in thalamus
- to primary auditory cortex (core) in superior temporal lobe in the lateral fissure
- to auditory association cortex (belt, parabelt)
Auditory input also goes to cerebellum and reticular formation

Question 8

core

Answer 8

• primary auditory cortex

- divided into 3 zones that receive input from 3 different areas of medial geniculate body

Question 9

belt

Answer 9

• first level of auditory association cortex
• At least 7 divisions
• Receives input from primary auditory cortex and medial geniculate body

Question 10

parabelt

Answer 10

• “highest level” of auditory association cortex

- Receives input from belt and medial geniculate body

Question 11

auditory posterior pathway

Answer 11

• From posterior parabelt to the posterior parietal cortex

- mediates sound localization (where)

Question 12

auditory anterior pathway

Answer 12

• From anterior parabelt to anterior temporal and inferior frontal
• mediates analysis of complex sounds (what)

Question 13

auditory cortex, fx and org

Answer 13

• Discriminating the identity of multiple sounds heard simultaneously is based on pattern recognition (we don’t know how)
• Pattern recog occurs in primary and association auditory cortex
• Different neurons in auditory cortex are arranged in columns (like visual cortex) that respond to different properties of sound stimulus:
• onset or cessation of sound, or both
• changes in pitch or intensity, sometimes only in one direction
• combinations of frequencies (i.e. complex stimuli)
• specific frequencies only in certain contexts – i.e. if it occurs at the beginning or end of a sequence

Question 14

damage to auditory cortex

Answer 14

Does not produce deafness
Impairs ability to distinguish rapidly/simultaneously occurring sounds - sound location, identity and/or movement
a. sound location = dorsal auditory association cortex
b. sound identity = ventral auditory association area
Auditory agnosia
- L lesions result in impaired speech content comprehension
- R lesions result in impaired speech prosody comprehension (and comp of non-speech sounds)

Question 15

initial pathway of auditory stimuli

Answer 15

Specific parts of the basilar membrane project to specific parts of the brain stem nuclei
- which project to specific parts of the inferior colliculus
- to specific parts of the medial geniculate body
- to specific parts of the primary auditory cortex
Different tones are processed in different modules