The collateral system of the medial nucleus of the trapezoid body of the cat, its neuronal architecture and relation to the olivo-cochlear bundle

Abstract

In rapid Golgi preparations several types of neurons and axonal endings are revealed in the medial trapezoid nucleus. The principal neuron, with tufted dendrites, receives the calyx of Held and endings of a peri-dendritic plexus. An elongate neuron is associated with various collateral endings of axons passing through the nucleus. A stellate neuron is associated with a peri-cellular axonal nest. The terminal branches of the peri-dendritic plexus are arranged in horizontal layers, which may provide for a tonotopic organization of the principal neurons across the dorsoventral axis of the nucleus. The dorsomedial peri-olivary nucleus, representing an origin of the crossed olivo-cochlear tract, contains elongate and radiate neurons. Its afferent plexus has a laminar arrangement, which may relate to a tonotopic organization of the olivo-cochlear bundle. Its plexus is formed chiefly by collaterals of axons entering or leaving the medial trapezoid nucleus. Collaterals from the calyciferous and peridendritic axons and from the axons of the principal neurons may permit the dorsomedial peri-olivary nucleus to monitor both the auditory input and output of the principal neurons of the medial trapezoid nucleus.