A specific pattern of connections from the sensorimotor region of the cerebral cortex to the thalamus in the rat.

In the course of an investigation of the thalamic connections of the frontoparietal cortex in the albino rat, lesions were placed in the parietal cortex of adult rats, and the resulting terminal degeneration was observed in the ventrobasal complex, using the Fink-Heimer silver impregnation technique. Lesions made in the primary somatosensory forelimb region of the cortex result in a narrow band of terminal degeneration which extends dorsoventrally throughout the rostrocaudal two-thirds of the ventrobasal complex. This portion of the ventrobasal complex coincides with the electrophysiological representation of the thalamic primary somatosensory forelimb area, and corresponds closely to the medial portion of the lateral part of the ventrobasal complex as described by Smith, as well as to the medial portion of the posterolateral ventral nucleus according to Matano et al. These results serve to confirm the close correlation determined electrophysiologically between the topographical organization of the somatosensory forelimb areas of both the parietal cortex and the ventrobasal complex of the rat thalamus.