title: Motor facilitation during action observation: The role of M1 and PMv in grasp predictions.
abstract: Recent theories propose that movement observation is not a "passive mirror" of ongoing actions but might induce anticipatory activity when predictable movements are observed, e.g., because the action goal is known. Here we investigate this mechanism in a series of 3 experiments, by applying transcranial magnetic stimulation (TMS) to primary motor cortex (M1) while subjects observed either whole hand or precision grasping performed by an actor. We show that corticomotor excitability changes in a grip-specific manner but only once the grip can be decoded based on the observed kinematic cues (Exp. 1). By contrast, presenting informative contextual precues evokes anticipatory modulations in M1 already during the reach phase, i.e., well before the grip type could be observed, a finding in line with a predictive coding account (Exp. 2). Finally, we used paired-pulse (PP) TMS to show that ventral premotor cortex (PMv) facilitates grip-specific representations in M1 but only while grip formation is observed. These findings suggest that PMv and M1 interact temporarily and mainly when motor aspects of hand-object interactions are extracted from visual information. By contrast, no sustained input from PMv to M1 seems to be required to maintain action representations that are anticipated based on contextual information or once the grip is formed (Exp. 3).
authors.affiliation: Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Belgium. Electronic address: Toon.deBeukelaar@faber.kuleuven.be.
authors.forename: Toon T
authors.initials: TT
authors.lastname: de Beukelaar
authors.affiliation: Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Belgium; Research Group for Neuromotor Rehabilitation, Department of Rehabilitation Sciences, KU Leuven, Belgium. Electronic address: Kaat.Alaerts@faber.kuleuven.be.
authors.forename: Kaat
authors.initials: K
authors.lastname: Alaerts
authors.affiliation: Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Belgium. Electronic address: Stephan.Swinnen@faber.kuleuven.be.
authors.forename: Stephan P
authors.initials: SP
authors.lastname: Swinnen
authors.affiliation: Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Belgium; Neural Control of Movement Group, Department of Health Sciences and Technology, ETH Zurich, Switzerland. Electronic address: nicole.wenderoth@hest.ethz.ch.
authors.forename: Nicole
authors.initials: N
authors.lastname: Wenderoth
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006225:Hand / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult
keywords: Human; Movement observation; Primary motor cortex; Transcranial magnetic stimulation; Ventral premotor cortex