title: Concurrent action observation modulates practice-induced motor memory formation.
abstract: Motor practice is associated with the formation of elementary motor memories. Here we tested in human subjects the hypothesis that observation of a motor training associated with physical practice will modulate the encoding process of a motor memory relative to physical practice alone. Voluntary thumb motions were practiced (i) alone in a direction opposite to the baseline direction of transcranial magnetic stimulation (TMS)-evoked movements (physical practice, PP) and in combination with observation of synchronous movements that were either (ii) directionally congruent (same direction, PP + AOc) or (iii) non-congruent (opposite direction, PP + AOnc) to the practiced ones. We evaluated the following measures of motor memory formation: percentage of TMS-evoked thumb movements falling in the direction of practiced motions, acceleration of TMS-evoked movements along the principal movement axis and corticomuscular excitability of training muscles as indexed by motor-evoked potential amplitudes. Both PP and PP + AOc, but not PP + AOnc, significantly increased the percentage of TMS-evoked movements falling in the practiced direction, changed the compound acceleration vector into the trained direction and enhanced the motor-evoked potential amplitudes in the training agonist muscle. The percentage of TMS-evoked movements falling in the practiced direction increased significantly more after PP + AOc than after PP. Across all measures of motor memory formation, PP + AOc was most efficacious, followed by PP and PP + AOnc. Action observation modulates practice effects on formation of a motor memory. Strengthening of the process of motor memory encoding depends on the directional congruency of the observed model.
authors.affiliation: Human Cortical Physiology Section and Stroke Neurorehabilitation Clinic, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: K
authors.initials: K
authors.lastname: Stefan
authors.forename: J
authors.initials: J
authors.lastname: Classen
authors.forename: P
authors.initials: P
authors.lastname: Celnik
authors.forename: L G
authors.initials: LG
authors.lastname: Cohen
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007100:Imitative Behavior / Q000502:physiology*; D007858:Learning / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D008959:Models, Neurological; D009044:Motor Cortex / Q000502:physiology; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology; D013663:Teaching; D013933:Thumb / Q000294:innervation / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*