title: Nothing magical: pantomimed grasping is controlled by the ventral system.
abstract: In a recent amendment to the two-visual-system model, it has been proposed that actions must result in tactile contact with the goal object for the dorsal system to become engaged (Whitwell et al., Neuropsychologia 55:41-50, 2014). The present study tested this addition by assessing the use of allocentric information in normal and pantomime actions. To this end, magicians, and participants who were inexperienced in performing pantomime actions made normal and pantomime grasps toward objects embedded in the Müller-Lyer illusion. During pantomime grasping, a grasp was made next to an object that was in full view (i.e., a displaced pantomime grasping task). The results showed that pantomime grasps took longer, were slower, and had smaller hand apertures than normal grasping. Most importantly, hand apertures were affected by the illusion during pantomime grasping but not in normal grasping, indicating that displaced pantomime grasping is based on allocentric information. This was true for participants without experience in performing pantomime grasps as well as for magicians with experience in pantomiming. The finding that the illusory bias is limited to pantomime grasping and persists with experience supports the conjecture that the normal engagement of the dorsal system's contribution requires tactile contact with a goal object. If no tactile contact is made, then movement control shifts toward the ventral system.
authors.affiliation: Research Institute MOVE Amsterdam, Faculty of Behavioural and Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands.
authors.forename: Thijs
authors.initials: T
authors.lastname: Rinsma
authors.affiliation: Research Institute MOVE Amsterdam, Faculty of Behavioural and Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands. j.vander.kamp@vu.nl.|Institute of Human Performance, University of Hong Kong, Hong Kong SAR, China. j.vander.kamp@vu.nl.
authors.forename: John
authors.initials: J
authors.lastname: van der Kamp
authors.affiliation: Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, UK.
authors.forename: Matt
authors.initials: M
authors.lastname: Dicks
authors.affiliation: Institute of Sport Science, Friedrich-Schiller-University Jena, Jena, Germany.
authors.forename: Rouwen
authors.initials: R
authors.lastname: Cañal-Bruland
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: Allocentric information; Grasping; Pantomime; Two-visual systems; Visual illusion