title: Corticospinal excitability is specifically modulated by the social dimension of observed actions.
abstract: A large body of research reports that perceiving body movements of other people activates motor representations in the observer's brain. This automatic resonance mechanism appears to be imitative in nature. However, action observation does not inevitably lead to symmetrical motor facilitation: mirroring the observed movement might be disadvantageous for successfully performing joint actions. In two experiments, we used transcranial magnetic stimulation (TMS) to investigate whether the excitability of the corticospinal system was selectively modulated by the social dimension of an observed action. We recorded motor-evoked potentials (MEPs) from right-hand muscles during the observation of an action sequence which, depending on context, might or might not elicit a complementary response. The results demonstrate a differential motor facilitation depending on action context. Specifically, when the context called for a complementary action, the excitability pattern reflected the under-threshold activation of a complementary action, whereas when the context did not imply acting in a complementary manner, the observer's corticospinal activity reflected symmetrical motor resonance. We contend that the mechanisms underlying action observation are flexible and respond to contextual factors that guide the social interaction between individuals beyond emulation.
authors.affiliation: Department of General Psychology, University of Padova, via Venezia 8, 35131 Padova, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Sartori
authors.forename: Andrea
authors.initials: A
authors.lastname: Cavallo
authors.forename: Giulia
authors.initials: G
authors.lastname: Bucchioni
authors.forename: Umberto
authors.initials: U
authors.lastname: Castiello
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007092:Imagination / Q000502:physiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D009474:Neurons / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*