title: Distorting the visual size of the hand affects hand pre-shaping during grasping.
abstract: Vision of the body is known to affect somatosensory perception (e.g. proprioception or tactile discrimination). However, it is unknown whether visual information about one's own body size can influence bodily action. We tested this by measuring the maximum grip aperture (MGA) parameter of grasping while eight subjects viewed a real size, enlarged or shrunken image of their hand reaching to grasp a cylinder. In the enlarged view condition, the MGA decreased relative to real size view, as if the grasping movement was actually executed with a physically larger hand, thus requiring a smaller grip aperture to grasp the cylinder. Interestingly, MGA remained smaller even after visual feedback was removed. In contrast, no effect was found for the reduced view condition. This asymmetry may reflect the fact that enlargement of body parts is experienced more frequently than shrinkage, notably during normal growth. In conclusion, vision of the body can significantly and persistently affect the internal model of the body used for motor programming.
authors.affiliation: Department of Neuroscience, University of Parma, Via Volturno 39, 43100 Parma, Italy.
authors.forename: Barbara F M
authors.initials: BF
authors.lastname: Marino
authors.forename: Natale
authors.initials: N
authors.lastname: Stucchi
authors.forename: Elena
authors.initials: E
authors.lastname: Nava
authors.forename: Patrick
authors.initials: P
authors.lastname: Haggard
authors.forename: Angelo
authors.initials: A
authors.lastname: Maravita
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D009043:Motor Activity; D011601:Psychophysics; D013647:Task Performance and Analysis; D014796:Visual Perception