Grab an object with a tool and change your body: tool-use-dependent changes of body representation for action

Along the evolutionary history, humans have reached a high level of sophistication in the way they interact with the environment. One important step in this process has been the introduction of tools, enabling humans to go beyond the boundaries of their physical possibilities. Here, we focus on some "low level" aspects of sensorimotor processing that highlight how tool-use plays a causal role in shaping body representations, an essential plastic feature for efficient motor control during development and skilful tool-use in the adult life. We assess the evidence supporting the hypothesis that tools are incorporated in body representation for action, which is the body schema, by critically reviewing some previous findings and providing new data from on-going work in our laboratory. In particular, we discuss several experiments that reveal the effects of tool-use both on the kinematics of hand movements and the localization of somatosensory stimuli on the body surface, as well as the conditions that are necessary for these effects to be manifested. We suggest that overall these findings speak in favour of genuine tool-use-dependent plasticity of the body representation for the control of action.