A BIMODAL MAP OF SPACE - SOMATOSENSORY RECEPTIVE-FIELDS IN THE MACAQUE PUTAMEN WITH CORRESPONDING VISUAL RECEPTIVE-FIELDS

The macaque putamen contains neurons that respond to somatosensory sti muli such as light touch, joint movement, or deep muscle pressure. The ir receptive fields are arranged to form a map of the body. In the fac e and arm region of this somatotopic map we found neurons that respond ed to visual stimuli. Some neurons were bimodal, responding to both vi sual and somatosensory stimuli, while others were purely visual, or pu rely somatosensory. The bimodal neurons usually responded to light cut aneous stimulation, rather than to joint movement or deep muscle press ure. They responded to visual stimuli near their tactile receptive fie ld and were not selective for the shape or the color of the stimuli. F or cells with tactile receptive fields on the face, the visual recepti ve field subtended a solid angle extending from the tactile receptive held to about 10 cm. For cells with tactile receptive fields on the ar m, the visual receptive field often extended further from the animal. These bimodal properties provide a map of the visual space that immedi ately surrounds the monkey. The map is organized somatotopically, that is, by body part, rather than retinotopically as in most visual areas . It could function to guide movements in the animal's immediate vicin ity. Cortical areas 6, 7b, and VIP contain bimodal cells with very sim ilar properties to those in the putamen. We suggest that the bimodal c ells in area 6, 7b, VIP, and the putamen form part of an interconnecte d system that represents extrapersonal space in a somatotopic fashion.