title: Human movements and abstract motion displays activate different processes in the observer's motor system.
abstract: Brain imaging studies have shown that observation of both bodily movements and abstract motion displays complying with human kinematics activate the observer's motor cortex. However, it is unknown whether the same processes are active in the two conditions. Here, we addressed this issue using transcranial magnetic stimulation (TMS) to directly compare cortico-spinal excitability during observation of actions and motion stimuli that complied with or violated normal human kinematics. We found that kinematics significantly modulated the motor-evoked potentials (MEPs) produced by TMS during observation of both human and abstract motion stimuli. However, only the temporal unfolding of cortico-spinal excitability during observation of human movements significantly correlated with instantaneous stimulus velocity. This correlation was present for normal movements and also for a subset of the movements having unnatural kinematics. Furthermore, bodily movements for which we found no correlation between MEPs and stimulus velocity produced significantly higher MEPs. Our novel results suggest a dissociation in how human movements and abstract motion displays engage the observer's motor system. Specifically, while both stimulus types significantly activate the observer's motor cortex, only bodily movements produce patterns of cortico-spinal excitability that closely follow the velocity profile of the observed movement. This internal "re-enactment" of observed bodily movements seems to be only partially attuned to normal human kinematics.
authors: Center for Neurosciences and Cognitive Systems@UniTN, Istituto Italiano di Tecnologia, Via Bettini 31, 38068 Rovereto, Italy.
authors: Sara
authors: S
authors: Agosta
authors: Center for Neurosciences and Cognitive Systems@UniTN, Istituto Italiano di Tecnologia, Via Bettini 31, 38068 Rovereto, Italy; Berenson-Allen Center for Noninvasive Brain Stimulation and Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, 02115 Boston, USA.
authors: Lorella
authors: L
authors: Battelli
authors: Center for Neurosciences and Cognitive Systems@UniTN, Istituto Italiano di Tecnologia, Via Bettini 31, 38068 Rovereto, Italy; Department of Neurobiology, Harvard Medical School,200 Longwood Avenue, 02115 Boston, MA, USA. Electronic address: antonino_casile@hms.harvard.edu.
authors: Antonino
authors: A
authors: Casile
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001921:Brain / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009068:Movement; D010775:Photic Stimulation; D011712:Pyramidal Tracts / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult