Somatotopic organization of vibrissal responses in the ventro-basal complex of the rat thalamus.

1. The region of the ventro-basal complex (VB) of the thalamus responding to movements of the whiskers has been mapped electrophysiologically in rats under either urethane or barbiturate anaesthesia.2. Whisker responses were found in the dorso-medial part of VB throughout its rostro-caudal extent; they occupied one third to one half of the total VB region.3. Most cells responded to movements of only one whisker and the responses were somatotopically organized. The different horizontal lines of whiskers were represented at different rostro-caudal levels within the nucleus, the most dorsal line being represented most caudally. At each level the larger, more caudal whiskers were represented more dorsally and laterally than the smaller, more rostral whiskers.