Authors: Bonifazi, S.¹; Farnè, A.²; Rinaldesi, L.¹; Làdavas, E.³

Source: Journal of Neuropsychology, Volume 1, Number 1, March 2007 , pp. 101-114(14)

Abstract:

Several studies in humans and non-human primates have shown that tool-use can expand near peripersonal space (Farnè & Làdavas, 2000; Iriki, Tanaka, & Iwamura, 1996). In humans, the extension of the near peripersonal space is revealed by an increase in the severity of cross-modal extinction caused by visual stimulation at the distal edge of a rake after its use as a reaching tool. The crucial question addressed here concerns whether the dynamic re-sizing of the peri-hand space in humans constitutes a real spatial expansion of visual-tactile peri-hand area along the tool axis. Alternatively, it could constitute a shift of the integrative area from the hand towards the distal edge of the tool, or the formation of a novel visual-tactile integrative area at the same distal location (Holmes, Calvert, & Spence, 2004). We contrasted the alternative predictions made by these hypotheses in a group of RBD patients by probing, at different locations along the tool axis, the changes induced by tool-use on cross-modal extinction. By assessing the visual-tactile extinction near the hand, midway along the tool, and at the distal edge of the tool we found an increase in visual-tactile extinction after tool-use both at the middle and the distal location along the tool axis. In contrast, no change intervened at the hand proximity. These findings support the view that the tool-use dependent re-mapping of peri-hand space in humans consists of a continuous elongation of visual-tactile peri-hand area from the hand towards the tip of the tool.

Document Type: Research article

DOI: 10.1348/174866407X180846

Affiliations: 1: Istituto di Riabilitazione S.Stefano, Porto Potenza Picena, Macerata, Italy 2: INSERM, UMR-S 534, Espace & Action, Bron, France; Université Lyon 1, Biologie Humaine, France 3: Centro Studi e Ricerche in Neuroscienze Cognitive, Cesena, Italy