[UW Anatomy | Contents]

Function:
Convey auditory information received from auditory portion of C.N. VIII to auditory centers in the brainstem.

Pathway:
Peripheral processes of cells in the spiral (cochlear) ganglion convey information from auditory receptors (hair cells) that lie in the organ of Corti in the inner ear. The central processes of these spiral ganglion neurons, which comprise the auditory portion of C. N. VIII, terminate in the dorsal (to the inferior cerebellar peduncle) and ventral cochlear nuclei (level #4). Cells in the cochlear nuclei send their axons rostrally, where they can take several routes to reach the auditory midbrain, the inferior colliculus. Auditory structures involved in these ascending, bilateral pathways include the superior olive, the trapezoid body and the lateral lemniscus. Cells in the inferior colliculus project to the medial geniculate body (MGB), which lies in the thalamus. Cells in MGB project to auditory cortex, areas 41 and 42, which lies in the temporal lobe (transverse temporal gyri of Heschl).

Deficits:
Lesion in the auditory nerve or nuclei results in loss of hearing from the ear IPSI. to the lesion. Lesions of the other auditory brainstem structures results in "subtle" auditory deficits. There is a great deal of bilaterality in the organization of the ascending auditory pathways, so unilateral lesions in auditory nuclei central (more "upstream")to the dorsal and ventral cochlear nuclei do not result in a major hearing loss.

Other Note:
Just be able to trace a pathway from the receptor to the auditory cortex.