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Neuro Exam 3 > Auditory Tracts > Flashcards

Auditory Tracts Flashcards

1
Q
  • Primary afferents carrying auditory information to the brain come from which cranial nerve? Which part?
  • Where do they enter the brainstem?
  • Where do these primary afferents synapse
A
  • VIII (Vestibulocochlear)-Specifically the cochlear part
  • Enter brainstem @ pontomedullary junction
  • Primary afferents descend or ascend to synapse on ventral or dorsal cochlear nuclei in the brainstem
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2
Q
  • What is the function of the dorsal cochlear nucleus?
  • It is part of what auditory tract?
A
  • Receives primary afferent fibers containing information on:
    • Identifying sound source elevation
    • Identifying complex spectral characteristics of sounds
  • Monaural (Dorsal and Monaural both have an O)
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3
Q
  • What is the function of the ventral cochlear nucleus?
  • It is part of what auditory tract?
A
  • Receives primary afferent fibers from the cochlear portion of CN VII
    • Horizontal localization of sound
    • Anterior and posterior subdivisions (see physio)
  • Binaural
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4
Q
  • Describe the monaural tract
A
  1. Primary afferents from cochlear portion of CN VIII travel to the dorsal cochlear nucleus where they will synapse
  2. FIbers then CROSS and ascend in the lateral lemniscus
  3. These fibers will synapse on the inferior colliculi
  4. Axons from the inferior colliculi will travel through the brachium of the inferior colliculi to the medial geniculate nucleus (remember SLIM mnemonic for superior and inferior colliculi)
  5. Fibers from MGN will ascend thru the sublenticular limb of the internal capsule and travel to the primary auditory cortex
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5
Q
  • Describe the binaural tract
A
  • Primary afferent fibers of cochlear portion of CN VIII synapse in ventral cochlear nucleus
  • Axons project BILATERALLY by passing thru the trapezoid body to the superior olivary complex (pons)
  • Cell bodies from medial and lateral olivary nucleus ascend in lateral lemniscus to the inferior colliculus
  • Axons from inferior colliculus will travel through the brachium of the inferior colliculus to the MGN (medial geniculate nucleus) of the thalamus
  • Axons from MGN will travel through SUBLENTICULAR LIMB of the internal capsule and synapse on cells of primary auditory cortex
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6
Q
  • What layer of the primary auditory cortex do cells from the MGN synapse in?
  • What is another name for the primary auditory cortex?
A
  • Layer IV
  • Heschl’s gyrus
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7
Q
  • What are two rules to consider when discussing monaural and binaural auditory tracts?
A
  1. All nerve fibers from cochlea will synapse in one of the cochlear nuclei (ventral or dorsal or both)
  2. Fibers in brainstem cross multiple times
  3. ALL fibers will synapse in the following areas
    1. Inferior colliculus
    2. MGN
    3. Primary Auditory Cortex
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8
Q
  • Lesions that occur in the brainstem and damage the vestibulocochlear n will or will not cause deafness?
A
  • Will not.
    • Fibers cross too many times at that point
    • Will have issues localizing sounds but will still be able to hear
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9
Q
  • Where are three places that auditory nerve fibers cross?
A
  1. Trapezoid body (between medial and lateral superior olivary nuclei)
  2. Lateral lemniscus
  3. Brachium of inferior colliculus
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10
Q
  • Conduction deafness versus
  • Sensorineural deafness versus
  • Central deafness
A
  • Conduction deafness
    • ​Problems with external or middle ear
    • Can’t conduct sound from the outside world into the inner ear
    • Transformation of sound to the tympanic membrane or thu ossicle chain
  • Sensorineural (Nerve) deafness
    • ​Damage to cochlea
    • Damage to cochlear part of CN VII or cochlear nuclei
    • Ipsilateral nerve deafness (fibers have not crossed yet)
  • Central
    • ​Damage to the central pathways (aka areas in the brainstem)
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11
Q
  • What does the basilar a. supply?
A
  • Cochlear
  • Auditory nuclei of pons and medulla
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12
Q
  • What does the labyrinthe (internal auditory) a. supply?
  • What is it a branch of?
A
  • Branch of AICA
    • Supplies inner ear and cochlear nuclei (esp in medulla)
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13
Q
  • What happens if there is an occlusion of the AICA
A
  • Monaural hearing loss (supplying cochlear nuclei in medulla before they have had the opportunity to cross?)
  • Can also damage facial nerve (Bell’s Palsy-ipsilateral facial paralysis) and pontine gaze center (inability to look towards side of lesion)
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14
Q
  • What do short circumferential branches of the basilar a supply?
A
  • Superior olivary complex
  • Lateral lemniscus
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15
Q
  • What do the superior cerebellar and quadrigeminal a’s supply?
A
  • Inferior colliculus
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16
Q
  • What do the thalamogeniculate arteries supply?
A
  • Medial geniculate bodies of thalamus
17
Q
  • What does M2 supply?
A
  • M2=branch of middle cerebral a.
  • Supplies primary auditory and association cortices
18
Q
  • What makes up Wernicke’s area and what is its function?
  • On what side is it most common (AKA dominant side)?
A
  • Wernicke’s area:
    • Supramarginal gyrus (part of parietal)
    • Angular gyrus (part of parietal)
    • Parts of superior temporal gyrus
  • Function
    • Comprehension of spoken language
  • Most people-LEFT hemisphere
19
Q
  • What makes up Broca’s area? What is the function of this area?
  • What lobe is it dominant in?
A
  • Broca’s area
    • Opercular gyrus
    • Triangular gyrus
    • Both of these gyri are parts of the inferior frontal gyrus
  • Function
    • Instruction for language output
    • Planning movements to produce speech
    • Grammatical function of words (no ifs, ands or buts)
  • LEFT hemisphere
20
Q
  • What is the function of non-dominant lobe Wernicke area?
A
  • Interpreting nonverbal signals
    • EX: Shrugging shoulders means IDK
21
Q
  • What is the function of the non-dominant Broca’s area
A
  • Instructions for producing non-verbal communication
    • Emotional gestures (flipping someone off)
    • Intonation of speech (George is here. vs George is here?)
22
Q
  • What is the pathway of auditory information from the primary auditory cortex to the action of producing actual speech?
A
  1. Auditory discrimination (Primary auditory Cortex)
  2. Classifying sounds (Auditory association cortex)
  3. Auditory comprehension (Wernicke’s)
  4. Linking understanding area (Wernicke’s) to speech area (Broca’s) via Arcuate fibers
  5. Instruction for language output (Broca’s)
  6. Cortical output to speech muscles (Oral and throat region of sensorimotor cortex)
23
Q
  • Visual word form area is important for what activity?
  • Lateral temporal cortex is important for _
A
  • Reading
  • Semantic knowledge (reading/seeing the word cat and knowing what that means)
24
Q
  • Auditory agnosia
A
  • Inability to describe a sound that has been heard
  • LESION IS UNIMODAL SENSORY ASSOCIATION CORTEX B/L (B/L TEMPORAL LESIONS REQUIRED TO DEVELOP AUDITORY AGNOSIA)
  • Damaging transverse temporal gyrus of Heschl
25
Q
  • Broca’s Aphasia (Expressive aphasia/Non-Fluent Aphasia)
    • ​Where is the lesion? Are the following functions intact?**​
    • Fluent?
    • Grammar?
    • Comprehension?
    • Naming?
    • Repitition?
A
  • Lesion in left inferior frontal gyrus (Broca’s area)
  • Non-fluent (impaired word formation)
  • Impaired grammar
  • Comprehension impaired for complex sentences
  • Naming is preserved
  • Repitition impaired for complex sentences

These people can understand what you are saying, but have a difficult time responding to what you are saying d/t inability to produce affluent speech

26
Q
  • Wernicke’s aphasia (Receptive or Fluent Aphasia)
    • ​Where is the lesion?
    • Are the following functions present?
      • ​Fluency
      • Grammar
      • Comprehension
      • Naming
      • Repitition
A
  • Lesion in left superior temporal gyrus, inferior parital lobule, posterior middle temporal gyrus
  • Are fluent
  • Grammar may be normal
  • Comprehension impaired even for single words
  • Naming is impaired
  • Repetition impaired for single words
27
Q
  • Conduction Aphasia
    • ​Where is the lesion?
    • Are the following functions present/absent?
      • ​Fluency
      • Grammar
      • Comprehension
      • Naming
      • Repitition
A
  • Lesion of arcuate fasciculus
  • Non-fluent
  • Grammar is preserved
  • Comprehension is normal
  • Naming is preserved
  • Repitition is preserved
28
Q
  • Transcortical motor lesions
    • ​Where is the lesion located?
    • Are the following functions absent/present:
      • ​Fluency
      • Grammar
      • Comprehension
      • Naming
      • Repitition
A
  • Lesion in ACA-MCA watershed area
  • Nonfluent
  • Grammar is preserved
  • Comprehension is normal
  • Naming is preserved
  • Repitition is preserved
29
Q
  • Transcortical sensory lesions
    • ​Where is the lesion located?
    • Are the following functions present/absent:
      • ​Fluency
      • Grammar
      • Comprehension
      • Naming
      • Repitition
A
  • Lesion in MCA-PCA watershed regions
  • Fluency is normal
  • Grammar preserved
  • Comprehension is impaired
  • Naming is impaired
  • Repitition is preserved
30
Q

Global lesions

A
  • Type of non-fluent aphasia
  • LESION OF LATERAL SULCUS (hitting both Broca’s and Wernicke’s)
  • Usually MCA issue
    *
31
Q
  • Transcortical lesions
A
  • Sensory or motor
  • Can repeat
32
Q
  • Conduction aphasia
A
  • Type of fluent aphasia
  • Lesion of supramarginal gyrus and arcuate fasciculus
  • Can’t repeat

Neuro Exam 3 (14 decks)

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