title: Grasping with tools: corticospinal excitability reflects observed hand movements.
abstract: Although facilitation of the corticospinal system during action observation is widely accepted, it remains controversial whether this facilitation reflects a replica of the observed movements or the goal of the observed motor acts. In the present study, we asked whether, when an object is grasped by using a tool, corticospinal facilitation represents 1) the movements of the hand, 2) the movements of the tool, or 3) the distal goal of the action. To address this question, we recorded motor-evoked potentials (MEPs) to transcranial magnetic stimulation while participants observed a hand reaching and grasping a mothball by using 3 types of pliers, requiring different hand-tool movements to achieve the same goal (grasping the object). We found that MEPs recorded from the opponens pollicis and from the first dorsal interosseous reflected the observed hand movements rather than the movements of the tool or the distal goal of the action. These results suggest that during observation of tool actions, detailed motor matching recruits online the same muscles as those used in the observed action.
authors.affiliation: Centre for Cognitive Science, Department of Psychology, University of Torino, 10123 Torino, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cavallo
authors.forename: Cristina
authors.initials: C
authors.lastname: Becchio
authors.forename: Luisa
authors.initials: L
authors.lastname: Sartori
authors.forename: Giulia
authors.initials: G
authors.lastname: Bucchioni
authors.forename: Umberto
authors.initials: U
authors.lastname: Castiello
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006225:Hand / Q000294:innervation / Q000502:physiology*; D006801:Humans; D007100:Imitative Behavior / Q000502:physiology*; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D015588:Observer Variation; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*; D053001:Tool Use Behavior / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult