01 avrSéminaire "Peripersonal Space: a multisensory interface for voluntary actions toward objects"01 avr 2011
Alessandro Farnè, INSERM - U864 Space and Action, Lyon, France
Friday, April 01 2011, 11h-12h30
Salle de réunion du LPP, H432, 4ème étage
Centre Biomédical des Saints Pères 45 rue des Sts Pères, 75006 Paris
Neurophysiological studies in monkeys described visuo-tactile neurons, presenting both tactile and visual receptive fields, the latter being limited to the space surrounding the former. Evidence is available both in neurotypical and brain-damaged populations about the existence of a similar Peripersonal Space (PpS) representation in humans.
We combined perceptual and kinematic recordings to probe the link between the PpS and the planning/execution of voluntary actions (i.e., grasping or pointing). In a series of experiments, participants grasped (or pointed to) an object while solving a tactile discrimination task on the acting right hand (Index finger=“top” or Thumb=“bottom”). We measured the visuo-tactile interference evoked by a visual distractor, appearing on the to-be-grasped object with congruent/incongruent elevation with the tactile target.
Visuo-tactile interference was modulated as a function of the action phase: stronger during planning and onset of the action than at baseline (before the action started). This increase was more important in the early (200ms after onset) and late execution phase (grip closing). This modulation on the right hand performance was effector-specific, being absent if the left hand was grasping. The kinematic differences between Grasping and Pointing were mirrored by different PpS modulations. Finally, similar modulations were also present in experienced participants who were merely observing (no action) someone else’s grasping.
These findings converge in showing that the PpS is a multisensory interface not only implied in defensive reactions, but also involved in the production of voluntary actions, as a function of the sensory-motor transformations and the kinematic demands specifically requested.