Auditory Pathways Flashcards
How is tone frequency detected relative to the cochlea?
High frequency tones register close to base of cochlea
Low frequency tones register distal to base of cochlea
All fibers in the cochlear nerve synapse in the cochlear nuclei on the _______ side
Ipsilateral
As cochlear info ascends to the auditory cortex, it is distributed through multiple parallel pathways that ultimately converge in the ______
Inferior colliculus
From the midbrain, auditory info is conveyed from the inferior colliculus to the _________ nucleus of the thalamus, then through the sublenticular limb of the _____ _____ to the auditory cortex
Medial geniculate; internal capsule
The spiral ganglion has 2 types of bipolar sensory neurons. What is the difference between the two?
Type I cells (90-95%) — 20+ radial branches synapse with 1-2 inner hair cells, respond to narrow frequency range
Type II ganglion cells — widely distributed peripheral processes that traverse the tunnel of Corti and synapse with 10+ outer hair cells. More sensitive to low-intensity sounds, less precisely tuned to frequency
As cochlear nerve fibers enter the brainstem at the cerebellopontine angle, they divide into ascending bundles and descending bundles.
Ascending bundles synapse in the _____ part of the ______ cochlear nucleus.
Anterior; anterior
[most fibers from anterior cochlear nucleus course anterior to restiform body part of inferior cerebellar peduncle to form the trapezoid body]
As cochlear nerve fibers enter the brainstem at the cerebellopontine angle, they divide into ascending bundles and descending bundles.
Descending bundles synapse in the _____ part of the ______ cochlear nucleus AND the _______ cochlear nucleus
Posterior; anterior; posterior
[projections from posterior cochlear nucleus and some from anterior cochlear nucleus course posteriorly over the restiform body as the posterior acoustic stria and decussate in the pontine tegmentum before joining the lateral lemniscus]
5 nuclei associated with primary auditory pathway
Cochlear nuclei Superior olivary nucleus Trapezoid body Nuclei of lateral lemniscus Inferior colliculus
Where is the first point in the primary auditory pathway at which decussation occurs?
Trapezoid body
It is possible to have a second order neuron proceed all the way up the auditory pathwway via the trapezoid body, bypassing the _____ nucleus and the nucleus of the _____ ____
Superior olivary; lateral lemniscus
3 primary fiber bundles that transmit info in the primary auditory pathway
Trapezoid body
Acoustic stria
Lateral lemniscus
What type of hearing loss results from damage to the cochlea or cochlear root of CN VIII
Sensorineural loss
Which type of hearing loss has no air or bone conduction when tested with Weber/Rinne?
Sensorineural
What type of hearing loss results from disease or damage to either external or middle ear?
Conductive hearing loss
With conductive hearing loss, _____ conduction is greater than _____conduction on Weber/Rinne test
Bone; air
During the Weber test, tuning fork is placed on the forehead or mastoid process. If sound lateralizes to the left ear, what are the 2 possible deficits indicated?
Conductive deficit in left ear
Sensorineural deficit in right ear
Result of unilateral dmaage to cochlear n. or cochlear nucleus
Ipsilateral monaural deafness
Result of unilateral damage at or above superior olivary complex
Inability to localize sounds, inattention to stimuli on contralateral side, or inability to follow conversations in a noisy room
What condition results from damage to the cochlear nuclei or the central pathways that relay auditory info to the auditory cortex?
Central deafness
Order of events in primary auditory pathway
Cochlea Spiral ganglion [CN VIII] Cochlear nucleus [trapezoid body] Superior olivary complex Nucleus of lateral lemniscus [lateral lemniscus] Inferior colliculus [brachium of inferior colliculus] Medial geniculate body Auditory cortex
[brackets = fibers between synapses]
The primary auditory cortex communicates with the auditory association cortex via the ____ ____
Arcuate fasciculus
The primary auditory cortex is located where?
Transverse gyri of Heschl
Brodmann area 41
The auditory association cortex surrounds the primary auditory area. It is located mainly in the _____ portion of the superior temporal gyrus and corresponds to Brodmann area _____
Posterior; 22
Sound localization based on timing is recognized by what component of the auditory pathway?
Medial superior olivary nucleus
[ex: talking to left ear, left medial superior olivary nucleus is hit first and trapezoid body on left will send glycine (inhib NT) to right side]
Localization based on sound intensity is recognized by what component of the auditory pathway?
Lateral superior olivary nucleus
[this is also known as coincidence detection]
What component of the auditory pathway has a protective mechanism to dampen sound from medial to lateral?
Olivocochlear bundle
Which brodmann areas are associated with reflex to turn head towards location of sound?
22
42
41
A lesion in which portion of the afferent acoustic pathway would lead to single-sided deafness?
Cochlear nucleus
Condition in which ability to hear sound is maintained but pt is unable to put meaning with it
Auditory agnosia
Result of damage to broca’s area
Understand speech but cannot formulate words to respond
Location of brocas area
Brodmanns 44 and 45
Located in pars opercularis and pars triangularis of inferior frontal gyrus — connected with auditory association cortex via arcuate fasciculus
Result of damage to wernicke’s area
Hear sound but cannot interpret speech
Location of wernicke’s area
Auditory association cortex — primarily in posterior portion of superior temporal gyrus, Brodmann area 22
Condition in which auditory comprehension is intact with fluent speech, but poor speech repetition
Conduction aphasia
Conduction aphasia usually involves damage to _____ _____ and left parietal region
Arcuate fasciculus
