Coding of modified body schema during tool use by macaque postcentral neurones

TLDR

Tools act as extensions of the hand both physically and perceptually, and body schemata are believed to underlie the assimilation of tool and hand. Macaques were trained to retrieve distant objects with a rake while neuronal activity was recorded in the caudal postcentral gyrus, where somatosensory and visual signals converge. Neuronal recordings revealed many bimodal neurons that encode the hand schema, whose visual receptive fields expanded to encompass the rake or its accessible space during tool use, indicating neural correlates of a modified hand schema that incorporates the tool.

Abstract

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 monkeys 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 use, their visual receptive fields were altered to include the entire length of the rake or to cover the expanded accessible space. These findings may represent neural correlates of the modified schema of the hand in which the tool was incorporated.