Auditory System Flashcards
Describe the dorsal and intermediate acoustic striae
Both decussate in upper medulla and ascend in contralateral lateral lemniscus (LL), which terminates upon neurons in inferior colliculus
Describe ventral acoustic stria
As these cross the medial lemniscus, they form the trapezoid body
Fibers terminate bilaterally in superior olivary nucleus
SON projects fibers to inferior colliculus through ipsilateral lateral lemniscus
Fibers from inferior colliculus project to ___. Fibers from this project to primary auditory cortex via ___
Medial geniculate body via brachium of inferior colliculus
Sublenticular (auditory) radiations
What directly links the auditory association area to Broca’s speech area in frontal lobe?
Superior longitudinal fasciculus
Where is the auditory association cortex for processing and integrating sounds?
In parieto-occipito-temporal (POT) association cortex and Wernicke’s area
What is the superior olivary nuclear complex?
It represents collections of nuclei dispersed along ascending auditory pathway.
They play a role in modifying auditory information
Describe medial and lateral superior olivary nuclei
Medial superior olivary nucleus is important for localizing sounds
Lateral superior olivary nucleus gives rise to most of olivocochlear efferents, which exert inhibitory influences upon organ of Corti.
Peripherally, the fibers pass through vestibular division and cross over to cochlear division via vestibulocochlear anastomosis
What does a unilateral lesion of the cochlear nerve result in?
Ipsilateral complete deafness
What does a unilateral lesion of the central auditory pathway result it?
Bilateral diminution of hearing which is more prominent in contralateral ear
These structures include lateral lemniscus, inferior colliculus, and brachium, and most geniculate body
What is conduction aphasia?
Results from a lesion in arcuate fasciculus
This fluent language disorder is characterized by severe impairment of repetition, difficulty in reading aloud (reading comprehension is intact), marked paraphasia, severe anomia, and a normal auditory comprehension
Right hemiparesis and hemianopia as well as orofacial and bilateral limb apraxia may be present
What is auditory agnosia?
Result from lesions in auditory association cortex
Characterized by an inability to comprehend auditory information
Spoken and written language as well as other sensory modalities may remain intact
What is Wernicke’s aphase (fluent paragrammatical aphasia)
Due to damage to Wernicke’s area in dominant hemisphere
This phasic zone appears to be an assembly area for critical components of language
Characterized by patient’s inability to comprehend spoken or written word
Patients can speak fluently, but their speech patterns demonstrate numerous word substitutions, neologisms (new word creations), and a circumlocution of language that belies an underlying fundamental comprehension deficit
Describe the primary neuron for the auditory system
In the spiral ganglion which is embedded in modiolus
The cochlear division of VIII nerve is formed by central processes of these bipolar neurons
On the posteriorlateral aspect of the upper medulla, these central processes terminate in dorsal (acoustic tubercle) and ventral cochlear nuclei
