GA: Auditory Pathways Flashcards
What are the 2 types of auditory pathways?
- Primary afferent CN 8 cochlear part
- Cochclear nuclei
Where are cell bodies located in the primary afferent CN 8 cochlear part?
In the spiral ganglion
Horizontal localization of the sound is accomplished via?
Ventral cochlear nucleus
Identifying sound source elevation is accomplished via?
Dorsal cochlear nucleus
In a monaural tract, information about sounds from a single ear is routed to?
The contralateral side
Where do monaural tracts cross?
In the dorsal cochlear nucleus (via dorsal acoustic stria)
What is the pathway for the monaural tract?
Dorsal cochlear nucleus –> cross –> lateral lemniscus (ascend) –> Brachium of Inferior Colliculus –> Medial geniculate nucleus –> Primary auditory complex (Heschl’s gyrus)
What is binaural information?
Information about differences between sounds at both ears
Where does binaural information project bilaterally to?
Trapezoid body
What is the tract for binaural information?
Ventral cochlear nuclei –>bilateral to trapezoid body –> superior olivary complex –> lateral leminiscus –> brachium of inferior colliculus –> medial geniculate nucleus –> layer 4 of primary auditory cortex (Heschl’s gyrus)
For auditory paths, where does everything eventually synapse?
Primary auditory complex
Medial geniculate nucleus
Inferior colliculus
If you damage some of the itty bitty auditory pathways, will you go deaf?
NO
There is way too much crossing in the auditory pathways.
crosses @ trapezoid body, posterior acoustic stria, commissure of inferior colliculus
But, you will have trouble localizing sound.
Define conduction deafness:
External/middle ear problem from an obstruction that prevents sound from crossing the tympanic membrane properly.
If you have damage to the cochlear part of CN 8 what happens?
Ipsilateral deafness
If you have damage to the central pathways in the ear what happens?
You won’t be able to localize sound
Blood supply for the cochlea + auditory nuclei of pons + medulla:
Basilar A.
Which artery supplies the inner ear + cochlear nuclei?
Internal auditory (labyrinthine) A. –> branch off AICA
What type of hearing loss will you get if you occlude the AICA?
Monaural hearing loss w/ possible ips. facial paralysis (facial N. runs through there)
What do the short circumferential branches of the basilar A. supply?
Superior olivary complex + lateral leminiscus
What supplies the inferior colliculus?
Superior cerebellar + quadrigeminal A.’s
What do the thalamogeniculate A.’s supply?
the medial geniculate bodies
What supplies the primary auditory + association cortices?
M2 segment of the middle cerebral A.
Which hemisphere is dominant in 94% of adults?
Left
Rt. handed = left side dominant
What does Wernicke’s area do?
Comprehension of spoken language
Trying to think of a word
What does Broca’s area do?
Produces speech (motor aspect)
grammar
Instructions for language output
What is the function of the area analogous to Wernicke’s?
Interpreting nonverbal signals from other people
Sarcasm
Pitch/tone of voice to phrase as a question
What is the function of the area analogous to Broca’s area?
Instructions for producing non-verbal communication including emotional gestures + intonation of speech
What is the function of the arcuate fibers and what do they connect?
Arcuate fibers allow you to repeat things (word repitition)
They connect Wernicke’s + Brocas
In the parietal lobe, what 3 things form Wernicke’s area?
- Superficial temporal gyrus
- Angular gyrus
- Supramarginal gyrus
What does the lateral temporal cortex do?
Word recognition
What does motor programs for articulation?
Dorsal premotor cortex
The inability to describe a sound that has been heard (ex. fire alarm) =
Auditory agnosia
A lesion of the unimodal sensory association cortex produces what symptom?
auditory agnosia
Wernicke’s aphasia is due to a lesion of wernicke’s area (temporal). What does this mean?
They can’t understand what is being said to them. They can speak fine, but like if you say the word cat, it means nothing to them. If you talk to them their responses back to you won’t make sense.
They aren’t really aware that they can’t understand you. They can’t read/write
If someone has lost the abillity to speak fluently, this likely means they have a lesion in ___________.
Broca’s area (left inferior frontal gyrus)
They often get frustrated + depressed and leave out their ands, ifs, and buts (less severe). More severe = mutism
A global lesion means:
Both Wernickes + Brocas areas got hit (lesion of lateral sulcus), and the person won’t even speak usually.
An infarction in the ACA-MCA border zone produces:
Transcortical motor lesion
An infarction in the MCA-PCA border zone produces:
Transcortical sensory lesion
A lesion of the supramarginal gyrus + arcuate fasciculus causes what?
Conduction aphasia
-can’t repeat, but fluency = intact
How does a transcortical motor aphasia present?
Like Broca’s but CAN REPEAT
What is anomic aphasia?
They can’t think of what the word is
How does transcortical sensory aphasia present?
Like Wernicke’s, but they CAN REPEAT
