Auditory Pathways Flashcards
What is the primary afferent CN VIII cochlear path?
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
What do the dorsal and ventral cochlear nuclei do?
dorsal: IDs sound source elevation and complex spectral characteristics of sound
Ventral: horizontal localization of sound (ant and post parts)
What is the monaural tract?
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
Where do all cells from the spiral ganglion synapse?
in cochlear nuclei
Why is the crossing in the auditory pathway significant?
bc there is so much crossing, if you lesion 1 thing –> will not be deaf
What is conduction deafness?
deficit related to an obstructed or altered transformation of sound to tympanic membrane or thru ossicle chain
What is sensorineural deafness?
results from damage to the cochlea, cochlear part of CN 8 or to the cochlear nuclei –> ipsi N deafness
What is central deafness?
damage to the central pathways
What supplies blood to the cochlea and auditory nuclei of pons and medulla?
basilar artery
What supplies blood to the inner ear and cochlear nuclei?
labyrinthine/internal auditory A = usually a branch of AICA
How would occlusion of the AICA affect hearing?
(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
What supplies blood to the superior olivary complex and lateral lemniscus?
short circumferential branches of the basilar A
What supplies blood to the inferior colliculus?
superior cerebellar and quadrigeminal As
What supplies blood to the medial geniculate bodies?
thalamogeniculate As
What supplies blood to the primary auditory and association cortices?
M2 segment of MCA
What does the area analogous to Wernicke’s do?
interprets nonverbal signals from other people
What does the area analogous to Broca’s do?
instructions for producing non-verbal communication including emotional gestures and intonation of speech
What is the arcuate fasciculus involved in?
word repetition
What is the lateral temporal cortex involved in?
semantic knowledge
word recognition/meaning
What is auditory agnosia?
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
Where is Wernicke’s area?
superior temporal gyrus
angular gyrus
supermarginal gyrus
What is global aphasia?
non-fluent aphasia: receptive and expressive deficits
lesion of lateral sulcus
reading and writing impaired
What is transcortical aphasia?
sensory or motor
can repeat
What is conduction aphasia?
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
What infarctions can cause transcortical motor or sensory aphasia?
motor: ACA-MCA border zone infarction
sensory: MCA-PCA border zone infarction
