Auditory Pathways

Question 1

What is the primary afferent CN VIII cochlear path?

Answer 1

cell bodies in spiral ganglion –> enter brainstem at pontomedullary jxn –> div into ascending and descending bundles –>

ascending –> ant part of ventral cochlear nucleus

descending –> post div of ventral cochlear n and in dorsal cochlear nucleus

Question 2

What do the dorsal and ventral cochlear nuclei do?

Answer 2

dorsal: IDs sound source elevation and complex spectral characteristics of sound

Ventral: horizontal localization of sound (ant and post parts)

Question 3

What is the monaural tract?

Answer 3

cochlear div of CN 8 –> dorsal cochlear nuclei –> cross at dorsal acoustic stria –> lateral lemniscus –> synapse at inf colliculus –> 2ndary neuron thru brachium –> synapse at med colliculus –> 3rd neuron thru sublenticular part of int capsule –> layer IV of primary auditory cortex

Question 4

Where do all cells from the spiral ganglion synapse?

Answer 4

in cochlear nuclei

Question 5

Why is the crossing in the auditory pathway significant?

Answer 5

bc there is so much crossing, if you lesion 1 thing –> will not be deaf

Question 6

What is conduction deafness?

Answer 6

deficit related to an obstructed or altered transformation of sound to tympanic membrane or thru ossicle chain

Question 7

What is sensorineural deafness?

Answer 7

results from damage to the cochlea, cochlear part of CN 8 or to the cochlear nuclei –> ipsi N deafness

Question 8

What is central deafness?

Answer 8

damage to the central pathways

Question 9

What supplies blood to the cochlea and auditory nuclei of pons and medulla?

Answer 9

basilar artery

Question 10

What supplies blood to the inner ear and cochlear nuclei?

Answer 10

labyrinthine/internal auditory A = usually a branch of AICA

Question 11

How would occlusion of the AICA affect hearing?

Answer 11

(labyrinthine branches of AICA –> inner ear and cochlear nuclei)

would cause monaural hearing loss

may also damage facial N and pontine gaze center –> ipsi facial paralysis and inability to look toward side of lesion

Question 12

What supplies blood to the superior olivary complex and lateral lemniscus?

Answer 12

short circumferential branches of the basilar A

Question 13

What supplies blood to the inferior colliculus?

Answer 13

superior cerebellar and quadrigeminal As

Question 14

What supplies blood to the medial geniculate bodies?

Answer 14

thalamogeniculate As

Question 15

What supplies blood to the primary auditory and association cortices?

Answer 15

M2 segment of MCA

Question 16

What does the area analogous to Wernicke’s do?

Answer 16

interprets nonverbal signals from other people

Question 17

What does the area analogous to Broca’s do?

Answer 17

instructions for producing non-verbal communication including emotional gestures and intonation of speech

Question 18

What is the arcuate fasciculus involved in?

Answer 18

word repetition

Question 19

What is the lateral temporal cortex involved in?

Answer 19

semantic knowledge

word recognition/meaning

Question 20

What is auditory agnosia?

Answer 20

inability to ID an object despite being able to perceive it

inability to describe a sound that has been heard

lesion: unimodal sensory association cortex bilaterally

Question 21

Where is Wernicke’s area?

Answer 21

superior temporal gyrus

angular gyrus

supermarginal gyrus

Question 22

What is global aphasia?

Answer 22

non-fluent aphasia: receptive and expressive deficits

lesion of lateral sulcus

reading and writing impaired

Question 23

What is transcortical aphasia?

Answer 23

sensory or motor

can repeat

Question 24

What is conduction aphasia?

Answer 24

type of fluent aphasia

lesion of supramarginal gyrus and arcuate fasiculus

can’t repeat

intact fluency

good comprehension

word-finding difficulties

reading intact, writing impaired

Question 25

What infarctions can cause transcortical motor or sensory aphasia?

Answer 25

motor: ACA-MCA border zone infarction
sensory: MCA-PCA border zone infarction