The projection of the acoustic nerve to the ventral cochlear nucleus of the rat. A Golgi study

Abstract

Acoustic nerve fibers, stained by the rapid Golgi method, were observed to bifurcate, after entering the ventral cochlear nucleus, into an ascending and a descending branch. Each branch was composed of fibers running parallel to each other with very little overlap. Prior to bifurcating, the acoustic nerve fibers gave rise to collaterals which ramified in the region of the bifurcations. Ascending branch fibers terminated in bulbs of Held and bore from zero to five additional collateral endings, including bulbs of Held. Descending, branch fibers gave rise within the posterior ventral cochlear nucleus to from zero to five collateral endings. These included large endings identified as bulbs of Held. Ascending and descending branch collaterals did not extend beyond 40–50 μ from their paret axons. Descending branch fibers projected into the dorsal cochlear nucleus. The area of the ventral cochlear nucleus dorsal to the region of bifurcations was innervated in a unique manner. This innervation occurred via long dorsally running collaterals arising from the most dorsal fibers of the ascending and descending branch projections.The data suggest morphological correlates of certain neurophysiological and behavioral findings in the areas of auditory localization and discrimination.