Retrograde degeneration study of somatic sensory thalamocortical connections in brain of Virginia opossum

Abstract

The method of retrograde degeneration was used to study thalamocortical relationship in the somatic sensory system of the forebrain of the Virginia opossum. Lesions were placed by aspiration in the primary somatic sensory cortex or subdivisions of it in 16 hemispheres and resultant retrograde degeneration in the ventrobasal complex and other thalamic nuclei was examined microscopically. Lesions placed in an electrophysiologically defined cortical region of representation of a given body part resulted in retrograde degenerative changes in the functionally corresponding part of the thalamic ventrobasal complex. Results are interpreted as supporting the hypothesis that axons of cells in the ventrobasal complex project upon the primary neocortical somatic sensory area in a topographic fashion, and thus the organization of somatic sensory thalamocortical projections in the opossum does not appear to be fundamentally different from that of eutherian mammals.