Ventral Nucleus Of The Trapezoid Body Research Articles

Origins of axons in the cat's acoustic striae determined by injection of horseradish peroxidase into severed tracts.

Origins and terminations of fibers of the dorsal and intermediate acoustic striae were studied by surgically severing these tracts and injecting HRP into the incision. This procedure results in filling the severed axons with HRP. Filled axons were traced to cell groups of origin and to some terminations of the acoustic striae. HRP-labeled terminals were found in the cochlear nuclei as well as in periolivary cell groups. Filling of cells with HRP RANged from being complete, resulting in Golgi-like images, to being barely detectable. Labeled cells were abundant in the dorsal and posteroventral cochlear nucleus adjacent to the injection as well as scattered throughout the periolivary cell groups of both sides, being highest in concentration around the ipsilateral lateral superior olive. On the side contralateral to the injection, labeled cells were found along the medial border of the dorsal cochlear nucleus, in the interstitial nucleus of the stria of Held, and sparsely throughout the ventral cochlear nucleus. The distribution of labeled cells was similar following HRP injections of the dorsal cochlear nucleus, except that these injections revealed additional descending projections from the inferior colliculi and from the ventral nucleus of the trapezoid body of both sides. These additional projections were interpreted as entering the CN by a ventral route. Findings of this study are in accord with physiological recordings made from fibers of the acoustic striae.

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

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.

Fiber degeneration following lesions in the anterior ventral cochlear nucleus of the cat

Lesions were made in the anterior ventral cochlear nucleus (AVCN) of the cat. Degeneration in the projections of the nucleus was studied with the Nauta and protargol methods. Degenerated fibers were found projecting to the lateral superior olivary nucleus and the lateral nucleus of the trapezoid body on the side of the lesion, and to the medial superior olivary nucleus, ventral and dorsal nuclei of the lateral lemniscus, and central nucleus of the inferior colliculus on both sides. Degeneration in the trapezoid body appears to have two fiber components: a dorsal portion that enters the contralateral medial superior olivary nucleus, and a ventral portion that does not. The AVCN has few, if any, projections to the posterior parts of the ipsilateral lateral nucleus of the trapezoid body, ipsilateral ventral nucleus of the trapezoid body, or to the contralateral medial nucleus of the trapezoid body. The orderly arrangement of the cochlear projection to the AVCN appears to be preserved in the projection of the AVCN to the superior olivary nuclei. The results suggest that two projections, differing in their course and connections, originate in a single subdivision of the AVCN.