Neural Activity in the Vestibular Nuclei of the Cat

Abstract

The responses of 600 single neurons in the vestibular nuclei of the cat to a constant angular acceleration (4°/sec²) or ice water caloric stimulation were investigated, and neurons were classified according to their responses. Animals were anesthetized and activity was recorded stereotaxically through the intact cerebellum with a tungsten microelectrode. The resting activity, response to stimulation, firing pattern, and relationship between spike discharge and nystagmus were the parameters of interest with special attention to the relationship between anatomy and neurophysiology of the vestibular nuclear complex. The results indicate that the superior and medial vestibular nuclei contains a relatively larger number of Type I and II neurons (related to semicircular ducts) and the lateral and inferior vestibular nuclei contains a relatively larger number of Type V neurons (related to otolith organs, spinal cord, etc.) which is in good agreement with anatomical findings. Histologic mapping according to their response type, however, shows no clear topographical arrangement. The average resting frequency was about 30 spikes per second, and the majority of neurons discharge pattern was random. Neuron firing in the nuclei was geared to the slow component of nystagmus. There is considerable crossed inhibitory activity between two sets of the vestibular nuclei.