title: Anticipatory planning reveals segmentation of cortical motor output during action observation.
abstract: It has been argued that the variation in brain activity that occurs when observing another person reflects a representation of actions that is indivisible, and which plays out in full once the intent of the actor can be discerned. We used transcranial magnetic stimulation to probe the excitability of corticospinal projections to 2 intrinsic hand muscles while motions to reach and grasp an object were observed. A symbolic cue either faithfully indicated the required final orientation of the object and thus the nature of the grasp that was required, or was in conflict with the movement subsequently displayed. When the cue was veridical, modulation of excitability was in accordance with the functional role of the muscles in the action observed. If however the cue had indicated that the alternative grasp would be required, modulation of output to first dorsal interosseus was consistent with the action specified, rather than the action observed--until the terminal phase of the motion sequence during which the object was seen lifted. Modulation of corticospinal output during observation is thus segmented--it progresses initially in accordance with the action anticipated, and if discrepancies are revealed by visual input, coincides thereafter with that of the action seen.
authors: Donders Institute for Brain, Cognition and Behaviour Behavioural Science Institute, Radboud University Nijmegen, Nijmegen, 6500 HE, The Netherlands Department of Clinical Epidemiology, VieCuri Medical Centre, Venlo, 5912 BL, The Netherlands.
authors: Loes
authors: L
authors: Janssen
authors: Behavioural Science Institute, Radboud University Nijmegen, Nijmegen, 6500 HE, The Netherlands.
authors: Bert
authors: B
authors: Steenbergen
authors: Trinity College Dublin, Trinity College Institute of Neuroscience and School of Psychology, Dublin 2, Ireland and School of Psychology, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland richard.carson@tcd.ie.
authors: Richard G
authors: RG
authors: Carson
mesh_terms: D000293:Adolescent; D000328:Adult; D059031:Anticipation, Psychological / Q000502:physiology*; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006225:Hand / Q000294:innervation / Q000502:physiology; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: human; motor cortex; reaching–grasping movement; transcranial magnetic stimulation; visuomotor