Auditory Pathways Flashcards
Auditory information is received by what nerve?
Cochlear nerve
Where does the cochlear nerve enter the brainstem?
Cerebellopontine angle
Once the cochlear nerve fibers enter the brain stem at the cerebellopontine angle, what happens?
Splits into ascending and descending bundles
Where does the ascending bundle synapse?
Anterior portion of the anterior cochlear nucleus
Where does the descending bundle synapse?
Posterior portion of the anterior cochlear nucleus AND
Posterior portion of the posterior cochlear nucleus
What information does the monaural tracts respond to?
Information about sounds at a SINGLE ear
Does the monaural tract stay ipsilateral or go contralateral?
Routes to the contralateral side
How does information in the monaural tract cross midline to target contralateral side?
Via the posterior acoustic stria
Describe the monaural tract
- Fibers from posterior cochlear nucleus ascend
- Cross midline via posterior acoustic stria
- Ascend via lateral lemniscus
- Synapse at inferior colliculus
- Synapse at medial geniculate nucleus
- Target primary auditory cortex
What nucleus does the monaural tract start at?
Posterior cochlear nucleus
What information does the binaural tracts respond to?
Manages information about differences between sounds at BOTH ears
What nucleus does the binaural tract start at?
Anterior cochlear nucleus
Fibers from the anterior cochlear nucleus ascend to where in the binaural tract?
Ipsilateral superior olivary complex AND
Contralateral superior olivary complex
How do fibers from the anterior cochlear nucleus ascend to the contralateral superior olivary complex?
Trapezoid body
What are the divisions of the superior olivary complex?
Medial superior olivary nucleus AND
Lateral superior olivary nucleus
The medial superior olivary nucleus transmits?
Time
The lateral superior olivary nucleus transmits?
Intensity
From the superior olivary complex, where do fibers ascend?
Lateral lemniscus
What are the divisions of the lateral lemniscus?
Central nucleus of lateral lemniscus AND
Posterior nucleus of lateral lemniscus
Where does the central nucleus of the lateral lemniscus send information?
To the inferior colliculus
Where does the posterior nucleus of the lateral lemniscus send information?
To the contralateral inferior colliculus
How does the posterior nucleus of the lateral lemniscus send information to the contralateral inferior colliculus?
Via the posterior tegmental commissure
Once at the inferior colliculus for the binaural pathway, where are fibers sent?
Medial geniculate nucleus and then on to the primary auditory cortex
The posterior nucleus of the lateral lemniscus receivers fibers from where?
Lateral superior olivary nucleus
Describe the binaural pathway
- Fibers from the anterior cochlear nucleus ascend to the ipsilateral and contralateral (via trapezoid body) superior olivary complex
- The superior olivary complex has a medial and lateral superior olivary nucleus
- Medial superior olivary nucleus relays time
- Lateral superior olivary nucleus relays intensity to posterior nucleus of lateral lemniscus
- Fibers ascend to lateral lemniscus divisions (central nucleus and posterior nucleus)
- Fibers are sent to the ipsilateral inferior colliculus by the central nucleus of lateral lemniscus
- Fibers are sent to the contralateral inferior colliculus by the posterior nucleus of the lateral lemniscus (via posterior tegmental commissure)
- Fibers synapse at MGN and primary auditory cortex
Blood supply to cochlea and auditory nuclei
Basilar
Blood supply to inner ear and cochlear nuclei
AICA/labyrinthine A.
Occlusion of AICA/labyrinthine A?
Monaural hearing loss, ipsilateral facial paralysis and inability to have horizontal gaze towards affected side
Blood supply to superior olivary complex and lateral lemniscus?
Short circumferential of basilar
Blood supply to inferior colliculus?
Superior cerebellar A.
Blood supply to Medial Geniculate Nucleus?
Thalamogeniculate A.s
Blood supply to Primary Auditory cortex?
M2 of MCA
The hemisphere that controls language is known as the ______ hemisphere
Dominant
What is normally the dominant hemisphere?
Left
Broca’s area
Production of language
Wernicke’s area
Comprehension of language
Connects Broca’s and Wernicke’s area
Arcuate fasciculus
What does the arcuate fasciculus allow us to do?
Speak, understand others and then respond appropriately
What is the normally non-dominant hemisphere?
Right
What is the right hemisphere responsible for?
NON-verbal communication
Prosody
Tone, stress, rhythm of speech (i.e. how to sound sarcastic and mad etc.)
What is in the right hemisphere?
Area analogous to Broca’s and Area analogous to Wernicke’s
Area analogous to Broca’s
Produces one’s own prosody of speech
Lesion to area analogous to Broca’s?
Motor aprosodia
Area analogous to Wernicke’s
Comprehends non-verbal communication
Lesion of area analogous to Wernicke’s?
Sensory aprosodia
When someone can perceive the sound but can NOT describe it
Auditory Agnosia
What causes auditory agnosia?
Bilateral lesions to anterior superior temporal lobes
Broca’s Aphasia
Patients have trouble producing speech, but can still comprehend everything, NO repetition
- Occlusion of M4 frontal MCA
Wernicke’s Aphasia
Patients can NOT comprehend language, talk endlessly with no meaning, NO repetition
- Occlusion of M4 temporal and parietal MCA
Global Aphasia
Damage to both Broca’s and Wernicke’s areas = loss of language completely
- Occlusion of left ICA
Conduction Aphasia
Interruptions of arcuate fasciculus
- Comprehension and speech production are intact but difficulty producing appropriate replies
Transcortical motor
Similar to Broca’s but repetition IS maintained
- Anterior watershed infarct
Transcortical sensory
Similar to Wernicke’s but repetition IS maintained
- Posterior watershed infarct
Mixed transcortical
Similar to global aphasia but has some comprehension and motor production
- Repetition IS maintained
