Auditory Tracts and Language Flashcards
Where are the cell bodies for primary afferents of CN VIII (cochlear part)?
Where do they enter the brainstem?
Where do they synapse?
Cell bodies are in the spiral ganglion.
They enter the brainstem at the pontomedullary junction.
They synapse at the cochlear nuclei.
Function of the dorsal cochlear nucleus (DCN):
To identify sound source elevation and changes in sounds.
Function of ventral cochlear nucleus (VCN):
To determine the horizontal localization of sound.
Monaural tract (5)
- Cell bodies from DCN cross to CL via acoustic stria.
- Fibers ascend in the lateral lemniscus.
- Synapse in the inferior colliculus.
- Fibers travel via the brachium of the inferior colliculus to the medial geniculate nucleus and synapse.
- Fibers synapse in layer IV of primary auditory cortex.
Binaural tract (4)
- Cell bodies from VCN project BL through the trapezoid body to superior olivary nucleus and synapse.
- Axons ascend in the lateral lemniscus to inferior colliculus and synapse.
- Axons travel via brachium of inferior colliculus to medial geniculate nucleus.
- Axons from MGN synapse in layer IV of primary auditory cortex.
Conduction deafness
Sensorineural deafness
Central deafness
Deficit from obstruction causing altered transmission of sound.
Damage to cochlea, cochlear part of CN VIII or cochlear nuclei.
Damage to central pathways.
BS to auditory nuclei of pons and medulla
Basilar a.
BS to inner ear and cochlear nuclei
Labyrinthine a. (from AICA).
What do the short circumferential branches of the basilar a. supply? (2)
Superior olivary complex
Lateral lemniscus
BS to inferior colliculus (2)
Superior cerebellar a.
Quadrigeminal a.
Thalamogeniculate a. supplies:
Medial geniculate bodies
M2 supplies:
Primary auditory and associated cortices.
Wernicke’s area (dominant)
Wernicke’s area (non-dominant)
Comprehension of spoken language
Interpreting non verbal signals
Broca’s area (dominant)
Broca’s area (non-dominant)
Producing speech
Producing non verbal communication, emotional gestures, and intonation of speech
Pathway of language comprehension to speaking (6)
- Primary auditory cortex
- Auditory association cortex
- Wernicke’s
- Subcortical connections (arcuate fibers)
- Broca’s
- Oral and throat regions of sensorimotor cortex
Lateral temporal cortex is used for:
Word understanding
Word retrieval
Wernicke’s
Arcuate fasciculus is used for:
Word repetition
Auditory agnosia
What is the lesion?
Cannot describe a sound that has been heard.
Lesion is unimodal sensory association cortex BL.
Wernicke’s aphasia (5)
Cannot comprehend language. Expression is fine. Cannot read. Cannot write. Display fluent paraphasic speech.
Broca’s aphasia (3)
Cannot speak fluently.
Can understand spoken and written language.
Spectrum d/o.
Global lesion (3)
Lesion of lateral sulcus.
Cannot hear or speak.
Poor reading and writing.
Transcortical sensory or motor aphasia
TCM is non fluent, understands fine, and can repeat.
TCS is fluent, does not understand, can repeat.
Which arteries are damaged to create Transcortical motor aphasia?
ACA-MCA border zone infarct
Which arteries are damaged to create Transcortical sensory aphasia?
MCA-PCA border zone infarct
Damage to what causes Broca’s aphasia?
Left inferior frontal gyrus
Damage to what causes Wernicke’s aphasia?
Left superior temporal gyrus
What layer of the primary auditory cortex does fibers in the auditory tracts synapse?
Layer IV
