4. 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 dorsal acoustic stria (pons)
- Fibers ascend in the lateral lemniscus.
- Synapse in the inferior colliculus (midbrain)
- Fibers travel via the brachium of the inferior colliculus to the medial geniculate nucleus and synapse (midbrain-diencephalon junction)
- Fibers synapse in layer IV of primary auditory cortex (heschl’s gyrus)
Binaural tract (4)
- Cell bodies from VCN project BL through the trapezoid body to superior olivary nucleus and synapse (pons)
- Axons ascend in the lateral lemniscus to inferior colliculus and synapse (midbrain)
- Axons travel via brachium of inferior colliculus to medial geniculate nucleus (midbrain-diencephalon junction)
- Axons from MGN synapse in layer IV of primary auditory cortex (heschl’s gyrus)
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 written and spoken language
Interpreting non verbal signals
Broca’s area (non-dominant)
Producing non verbal communication, emotional gestures, and intonation of speech (rise and fall of tone/voice in speech)
Pathway of language comprehension to speaking (6)
- Primary auditory cortex
- Auditory association cortex
- Wernicke’s
- Subcortical connections (arcuate fibers)
- Broca’s
- Pre-central gyrus (motor): Oral and throat regions of sensorimotor cortex
Lateral temporal cortex is used for:
- Word recognition (meaning)
- Semantic knowledge (meaning of a sentence)
Word retrieval and representation
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 aka "word salad"
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
dorsal premotor cortex function
motor programming for articulation
anomic aphasia
word finding difficulties
- repeats
- comprehends
- fluent
conduction aphasia, are they:
- fluent
- do they comprehend
- can they repeat?
lesion to the posterior inferior parietal lobe
- yes fluent
- yes comprehends
- no repeats
transcortical sensory aphasia, are they:
- fluent
- do they comprehend
- can they repeat?
- yes fluent
- no comprehension
- yes repeats
How can you tell transcortical sensory aphasia from Wernike’s aphasia?
*they are able to REPEAT
how can you tell transcortical motor aphasia from Broca’s aphasia?
- GRAMMAR is preserved in transcortical
- also Broca’s will have comprehension and repetition impairments for complex sentences
- Broca’s grammar not preserved: ex, emit words in a sentence that are not essential (telegraphic speech)
Wernike aphasia, are they:
- fluent
- do they comprehend
- can they repeat?
- yes fluent
- no comprehension
- no repeats
Transcortical motor aphasia, are they:
- fluent
- do they comprehend
- can they repeat?
- NO fluent
- YES comprehends
- YES repeats
Broca’s aphasia, are they:
- fluent
- do they comprehend
- can they repeat?
- NO fluent
- YES comprehends
- NO repeats
Mixed transcortical aphasia, are they:
- fluent
- do they comprehend
- can they repeat?
- NO fluent
- NO comprehension
- YES repeats
Global aphasia (aka massive stroke), are they:
- fluent
- do they comprehend
- can they repeat?
All NO
Broca’s area (dominant), what are its 4 functions?
- Producing speech
- instruction output for planning movements to produce speech (articulation)
- word processing
- grammar (syntax)
lesion to right (non-dominant hemisphere) to area analogous to Broca’s
have difficulty understanding intonation of speech. For example, not understanding sarcasm
what could lesion of M2 cause?
lesion of primary auditory cortex (brodmann area 41)
- difficulty interpreting sound or localizing in space
- no deafness
Lesion to Wernike’s area (non-dominant)
monotone, ‘robotic’ speech or fail to grasp nuances of intonation (termed aprosodia)
-inability of a person to properly convey or interpret emotional rhythm
lesion to the left inferior frontal gyrus causes what type of aphasia?
broca’s
lesion to what 4 areas can cause Wernicke’s aphasia?
- left superior temporal gyrus
- inferior parietal lobe
- posterior middle temporal gyrus
- Middle temporal gyrus
lesion to the arcuate fasciculus causes what type of aphasia?
conduction
lesion to the ACA-MCA border zone causes what type of aphasia?
transcortical motor
lesion to the MCA-PCA border zone causes what type of aphasia?
transcortical sensory
