CODING OF MODIFIED BODY SCHEMA DURING TOOL USE BY MACAQUE POSTCENTRALNEURONS

A tool is an extension of the hand in both a physical and a perceptual sense. The presence of body schemata has been postulated as the basis of the perceptual assimilation of tool and hand. We trained macaque m onkeys to retrieve distant objects using a rake, and neuronal activity was recorded in the caudal postcentral gyrus where the somatosensory and visual signals converge. There we found a large number of bimodal neurones which appeared to code the schema of the hand. During tool us e, their visual receptive fields were altered to include the entire le ngth of the rake or to cover the expanded accessible space. These find ings may represent neural correlates of the modified schema of the han d in which the tool was incorporated.