Auditory Paths

Question 1

Where do the ascending and descending bundles synapse respectively in the cochlear nuclei?

Answer 1

Ant. division of ventral cochlear nucleus

Post. division of ventral cochlear nucleus
and Dorsal cochlear nucleus

Question 2

What is the order of synapsing for the Monoaural tract?

Answer 2

single ear-routed to contralateral side

1. Start in Dorsal cochlear nucleus
   1a. cross via dorsal acoustic stria
2. ascend in the lateral lemniscus to synapse in Inferior Colliculus
3. travel in Brachium of the IColliculus to synapse in the Medial Geniculate Nucleus
4. travel in the Sublenticular limb of the Internal Capsule to synapse in the Primary Auditory Cortex (Heschl)

Question 3

What is the order of synapsing for the Binaural tract?

Answer 3

• 1. Start in the Ventral cochlear nuclei and project bilaterally through the Trapezoid body to the Superior Olivary complex
• 2. Medial and Lateral SO nucleus—-ascends in the lateral lemniscus to synapse in the Inferior Colliculus
     
     3. Travel via the Brachium of the IColliculus to synapse in the Medial Geniculate nucleus
     4. Travel through the Sublenticular limb of the IC to synapse in the Primary Auditory Cortex (Heschl)

Question 4

What is Conduction deafness?

Answer 4

obstructed or altered transformation of the sound to the tympanic membrane or through the ossicle chain (small bones)

Question 5

What is Sensorineural deafness?

Answer 5

damage to the cochlea (ipsilateral hair cells, spiral ganglion, etc)

Question 6

What is central deafness?

Answer 6

damage to central paths— rarely total deafness due to all the crossing points in the tract; but patients have trouble localizing sound, especially in louder, stimulating environments

Question 7

What is the blood supply of the cochlea and auditory nuclei of the pons/medulla?

Answer 7

Basilar A.

Question 8

What is the blood supply of the inner ear and cochlear nuclei?

Answer 8

Internal Auditory (Labyrinthine) A.—which is generally a branch of AICA

Question 9

What is the blood supply of the superior olivary complex and lateral lemniscus?

Answer 9

Short circumfereential branches of Basilar A.

Question 10

What is the blood supply of the inferior colliculus?

Answer 10

Superior Cerebellar and Quadrigeminal A.

Question 11

What is the blood supply of the medial geniculate bodies?

Answer 11

Thalamogeniculate A.

Question 12

What is the blood supply of the primary auditory and association corticies?

Answer 12

M2 segment of MCA

Question 13

Occlusion of AICA presents with what kind of hearing deficit?
Other non-hearing deficits?

Answer 13

• monaural hearing loss
• facial N. fibers and pontine gaze center (horizontal saccadic)… ipsilatereal facial paralysis + can’t look toward lesion side

Question 14

What is Wernicke’s area in charge of?

How would a lesion here present?

Answer 14

the comprehension of spoken and written language

Lesion: Wernicke’s aphasia (fluent)- can express language but lacks understanding and meaning through it—cannot write (agraphia) or read (alexia).
Will speak in a fluent, paraphrasic way (random assortment of words, some made up)

+patients are generally unaware of the issue

Question 15

What is Broca’s area in charge of?

How would a lesion here present?

Answer 15

• the instruction of language output
• Planning the movements needed for speech
• grammatical function of words

Lesion: Broca’s aphasia (non-fluent/expressive)- cannot speak fluently except for the most basic of sounds/words-which are spoken slowly, labored, w/ poor enunciation; however, they can understand spoken and written language

+Patients are generally aware of the issue- resulting in frustration and possibly depression

Question 16

The area analogous to Wenicke’s (generally on the right hemisphere) is in charge of what?

Answer 16

Interpreting nonverbal signals from other people

Question 17

What is the area analogous to Broca’s area (generally on the right) in charge of?

Answer 17

Producing the instruction for non-verbal communication- including emotional gestures and intonation (rising and falling of tone) of speech

Question 18

What is auditory agnosia?

What would have to happen lesion-wise (rare)?

Answer 18

AA: the inability to describe a sound that has been heard
-caused by a bilateral lesion of the unimodal sensory association cortex (from 2 different strokes or double sided trauma)

Question 19

Compare/Contrast:
Conduction aphasia
Transcortical aphasia (motor and sensory)

Answer 19

conduction: fluent; normal comprehension and naming ability; cannot repeat; lesioned in Arcuate Fasciculus

Transcortical (M): nonfluent; normal comprehension, naming, and repetition ability; lesioned in ACA-MCA border zone

Transcortical (S): fluent; impaired comprehension and naming; can repeat; lesioned in MCA/PCA border zone