Neuronal organization of the rabbit cochlear nucleus: some anatomical and electrophysiological observations

The cochlear nucleus of the young adult rabbit was studied using both anatomical and electrophysiological techniques. The cytoarchitecture of the cochlear nucleus, as revealed by Nissl-staining and Bodian's Protargol method, was quite similar to that of the cat. The cell types observed by the Golgi-Cox method were very similar to those observed in the cat cochlear nucleus. Bushy and stellate cells were predominant in the anterior ventral cochlear nucleus, and multipolar and globular cells were observed throughout the posterior ventral cochlear nucleus, surrounding a region containing mainly octopus cells. The dorsal cochlear nucleus was revealed as a limited structure with a prominent band of fusiform cells. The polymorphic layers continued varieties of giant neurons similar to those observed in the cat. Units in the cochlear nucleus were classified electrophysiologically, in terms of their discharge pattern, and located histologically. The ventral cochlear nucleus contained mainly "primarylike," "chopper" and "onset" units, but the dorsal cochlear nucleus contained a greater variety of response patterns. "Buildup," "pauser" and "chopper" response patterns were predominant, and the dorsal cochlear nucleus also obtained more inhibitory units than the ventral cochlear nucleus. Both the types of units observed and their location in each nucleus were very similar to those reported for the cat. Both divisions of the ventral cochlear nucleus and the dorsal cochlear nucleus were found to be tonotopically organized in a dorsal (high frequency) to ventral (low frequency) direction. A trend for an organization in a medial to lateral direction was also apparent, particularly in the dorsal cochlear nucleus.