Fiber degeneration following lesions in the multipolar and globular cell areas in the ventral cochlear nucleus of the cat

Abstract

A previous study with the Nauta method showed that lesions involving the octopus cell and caudal parts of the multipolar cell areas of the posteroventral cochlear nucleus of the cat produce degenerated fibers in the intermediate acoustic stria and trapezoid body which arborize in periolivary cell groups of the superior olivary complex both ipsilaterally and contralaterally. In the present study, using similar methods, lesions involving the rostral part of the multipolar cell area and adjacent parts of the globular cell area produced fine and coarse degenerated fibers in the caudal trapezoid body, but none in the intermediate acoustic stria. Ipsilaterally, sites of preterminal degeneration were largely co-extensive with those seen following lesions of the octopus cell and caudal multipolar cell areas, but included at least two projections not previously found. Contralaterally, projections were, in part, overlapping with, but were much more extensive than those from the caudal posteroventral cochlear nucleus. These differences, which include the demonstration of degenerated calyces of Held from large fibers of the trapezoid body, and fine preterminal degeneration in the ventral nucleus of the trapezoid body, are interpreted with respect to existing literature on the structure of the ventral cochlear nucleus and superior olivary complex. The data suggest that the ventral cochlear nucleus may be a complex of sub-nuclei each of which has its own set of output projections.