Auditory System Flashcards
primary neuron in the auditory pathway
- located in the spiral ganglion in the modiolus
- cochlear division of VIII N is formed by the central processes of bipolar neurons
- central processes terminate in the dorsal (acoustic tubercle) and ventral cochlear nuclei–in the upper medulla
dorsal and intermediate acoustic striae
- visible as the stria medullaris acoustic
- both decussate in the upper medulla and ascend in the lateral lemniscus
- LL terminates upon neurons in the inferior colliculus
ventral acoustic stria
- cross the medial lemniscus and form the trapezoid body
- fibers terminate bilaterally in the superior olivary nucleus (SON)
- SON projects fibers to the inferior colliculus primarily thru the ipsilateral lateral lemniscus
inferior colliculus and medial geniculate body
inferior colliculus–>brachium of inferior colliculus–>medial geniculate body–>sustentacular auditory radiations–>primary auditory cortex
primary auditory cortex
- located in the transverse and superior temporal gyri
- has a general tonotropic organization according to high freq in the caudal aspect and low freq in the rostral aspect
auditory assoc cortex
- for processing and integration of sounds
- located in the parieto-occipito-temporal assoc cortex and Wernicke’s area
- superior longitudinal fasciculus links the auditory assoc area to Broca’s speech area in the frontal lobe
superior olivary nuclear complex
- represents a collection of nuclei dispersed along the ascending auditory pathway
- play a role in modifying auditory info
- medial superior olivary nucleus–needed for localizing sounds
- neurons in the lateral superior olivary nucleus–gives rise to olivocochlear efferents which exert inhibitory influences upon the organ of Corti
- peripherally the fibers cross over to the cochlear division via the vestibulocochlear anastomosis
pathway for auditory information
primary neuron in spiral ganglion–>central processes of bipolar neurons form the cochlear N of VIII–>
- dorsal (acoustic tubercle) acoustic stria–>decussate in upper medulla–>ascend in contralateral lateral lemniscus–>inferior colliculus
- ventral acoustic stria–>cross the medial lemniscus and form the trapezoid body–>terminate bilaterally in superior olivary nucleus–>lateral lemniscus–>inferior colliculus
- ->brachium of inf colliculus–>medial geniculate body–>sustenticular auditory radiations–>primary auditory cortex
unilateral lesion of the cochlear N
results in ipsilateral complete deafness
unilateral lesion of the central auditory pathway
- results in bilateral diminution of hearing which is more prominent in the contralateral ear
- involves structures like the lateral lemniscus, inf colliculus, brachium of inf colliculus, and medial geniculate body
lesions of primary auditory cortex
result in difficulty localizing sounds and tone discrimination
-no hearing deficits
conduction aphasia
- lesion of the arcuate fasciculus
- results in conduction aphasia
- fluent language disorder
- characterized by severe impairment of repetition, difficulty reading aloud, marked paraphasia, severe anomia, and normal auditory comprehension
- right hemiparesis and hemianopsia, orofacial and bilateral limb apraxia may be presetn
auditory agnosia
- lesion in the auditory association (POT) cortex
- characterized by inability to comprehend auditory info
- spoken and written language and other sensory modalities in tact
fluent paragrammatical aphasia
- Wernicke’s Aphasia
- due to damage to Wernicke’s area of dominant hemisphere
- phasic zone appears to be an assembly area for the critical components of language
- characterized by pt’s inability to comprehend the spoken or written word
- pt’s speak fluently and their speech patterns have word substitutions, new word creations, and circumlocution of language
- also a receptive aphasia
