SINGLE NEURON INVESTIGATION OF SENSORY THALAMUS OF THE OPOSSUM

Abstract

A study was carried out to determine the sensitivity to auditory and somesthetic stimuli of individual neurons in the somesthetic region of the opossum thalamus, and to compare these results with the known properties of neurons in the ventro-posterior nucleus (VP) and the posterior group of nuclei (Po) of the cat. Clicks, light flashes, and electrical and mechanical skin stimuli were delivered to animals anesthetized with Dial-Urethane. Glass micropipettes and fine (25 [mu]) insulated nichrome wires served as electrodes. The placement of the electrodes was later established by a study of serial sections through the thalamus. The area intercalated between VP medially and the geniculate bodies laterally was found to contain neurons with properties typical of Po of the cat; thus, these areas in the 2 species are probably homologous, VP was found to have some neurons typical of VP of other mammals, but also some typical of Po. This suggests that Po may be the archetypical thalamic relay. Responses were also obtained in zona incerta.