TACTILE ACTIVITY IN PRIMATE PRIMARY SOMATOSENSORY CORTEX DURING ACTIVE ARM MOVEMENTS - CORRELATION WITH RECEPTIVE-FIELD PROPERTIES

1. Five hundred ninety-five single neurons with tactile receptive fiel ds (RFs) on the contralateral arm were isolated in the primary somatos ensory cortex (SI) of awake, behaving monkeys. 2. Fifty-eight percent of the tactile cells showed significantly different levels of activity during active movements of the arm in eight directions or during acti ve maintenance of the arm over the target endpoints. 3. The discharge of many of the active tactile cells was unimodally tuned with movement direction and the pattern of the tactile population activity varied i n a meaningful fashion with arm movement direction and posture. 4. The intensity of the arm-movement-induced activity was typically less tha n that evoked by direct tactile stimulation of the cell's RF. 5. The p robability of task-related activity was correlated with certain RF pro perties, in particular the sensitivity of the cell to lateral stretch of the skin and to passive arm movements that avoided direct contact o f the RF on any surface. 6. This suggests that task-related activity r esults mainly from the activation of tactile receptors by mechanical d eformation of the skin as the arm changes geometry during movement. 7. These results demonstrate that tactile activity containing potential proprioceptive information is generated in SI during active arm moveme nts that avoid direct contact of the skin with external surfaces. Whet her or not this input contributes to the kinesthetic sensations evoked by the movements cannot be resolved by this study.