Organization of the vestibular projection to the spinal cord of the cat.

Abstract

Results were obtained from recordings from 331 interneurons at cervical and lumbar levels of the cat spinal cord. The sites of responses to vestibular nerve (VN), dorsal root (DR) and/or motor cortex (MC) stimulation were plotted, and were correlated with cytoarchitechtonic laminae of the spinal gray, and with distribution of terminal degeneration caused by lesions in vestibular nuclei, reticular formation, dorsal roots, and motor cortex. Three populations of interneurons were found: those responding to VN stimulation alone; those responding to VN + DR stimulation; and, those responding to VN + MC stimulation; a few interneurons responded to stimulation of all three sources. Those of (a) above were localized medially, those of (b) centrally, and those of (c) laterally. Depolarizing and hyperpolarizing potentials and spike discharges were obtained in response to stimulation of the three sources. VN stimulation elicited responses from both dorsal and ventral roots, similar to those elicited by DR and MC stimulation. Thus the interneurons upon which the vestibular system projects, must at least in part, project presynaptic ally upon incoming dorsal root fibers.