Retinal innervation of the inferior colliculus in adult cats: electron microscopic observations

A moderate number of degenerating synaptic boutons (DSB) in the pericentral nucleus of the inferior colliculus (IC) were identified electron microscopically following contralateral eye enucleation in adult cats. Most of the DSB measure 0.6-1 micron and a lower percent are larger (1-2.5 micron). Both types contain a slightly polymorph population of clear vesicles, mainly round and oval, and a very few are elongated. The DSB are involved in asymmetric axodendritic contacts. The present report provides evidence for a crossed retinofugal monosynaptic excitatory tract innervating the IC pericentral nucleus, a possible audio-visual integrative subcortical center.