Somatic sensory representation in the thalamic ventrobasal complex of the Virginia opossum.

Abstract

AbstractThe present study was designed to investigate the topographic organization of somatic sensory representation in the thalamic ventrobasal complex (Vb) of the Virginia opossum. Tungsten and stainless steel micro electrodes were used to record the electrical activity of single units or single unit clusters in response to mechanical stimulation of the body surface, and the obtained data were used to construct maps of somatic sensory representation in transverse planes of the ventrobasal complex. The general pattern is similar to that found in eutherian mammals. A relatively large contralateral head and face representation is located throughout the entire anterior‐posterior extent of the ventrobasal complex, while a relatively smaller representation of contralateral trunk and limbs is located laterally only in the middle regions of the ventrobasal complex. Representations of middorsal head and trunk are located dorsally while those of limb apices are located ventrally. Activity was also recorded in the posterior nuclear region of the thalamus (Po) and in the subthalamic zona incerta (ZI), and there is a suggestion of topographic organization in these nuclear regions as well.