title: Dynamic size-change of hand peripersonal space following tool use.
abstract: Humans and monkeys share similar sensory integrated processing of tactile and peri-hand visual inputs for coding peripersonal space surrounding the hand. In monkeys, tool use is known to induce a transient elongation of hand-centred peripersonal space along the tool axis. Here we report evidence that, also in humans, the use of a tool can increase the spatial extent of the representation of peri-hand visual space to incorporate the tool. We investigated this phenomenon in patients with tactile extinction, by using a cross-modal paradigm well suited to reveal visual-tactile integration near patients' hand. In the present study cross-modal extinction was assessed far from patients' ipsilesional hand, at the distal edge of a hand-held rake. We found that cross-modal extinction was more severe after patients used the rake to retrieve distant objects with respect to a condition in which the rake was not used. This evidence of an expansion of peri-hand space lasted only a few minutes after tool use. By contrast, peri-hand space expansion was not observed when motor actions towards distant objects did not involve the tool. These findings show that visual peri-hand space has important dynamic properties in humans; it can be expanded and contracted depending upon tool use.
authors.affiliation: Department of Psychology, University of Bologna, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Farnè
authors.forename: E
authors.initials: E
authors.lastname: Làdavas
mesh_terms: D000368:Aged; D005260:Female; D006225:Hand / Q000502:physiology* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009473:Neuronal Plasticity; D010550:Personal Space; D010775:Photic Stimulation; D010812:Physical Stimulation; D020521:Stroke / Q000503:physiopathology; D014110:Touch / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology