title: Observation of interactive behavior increases corticospinal excitability in humans: A transcranial magnetic stimulation study.
abstract: In humans, observation of others' behaviors increases corticospinal excitability (CSE), which is interpreted in the contexts of motor resonance and the "mirror neuron system" (MNS). It has been suggested that observation of another individual's behavior manifests an embodied simulation of his/her mental state through the MNS. Thus, the MNS may involve understanding others' intentions of behaviors, thoughts, and emotions (i.e., social cognition), and may therefore exhibit a greater response when observing human-interactive behaviors that require a more varied and complex understanding of others. In the present study, transcranial magnetic stimulation was applied to the primary motor cortex of participants observing human-interactive behaviors between two individuals (c.f. one person reaching toward an object in another person's hand) and non-interactive individual behavior (c.f. one person reaching toward an object on a dish). We carefully controlled the kinematics of behaviors in these two conditions to exclude potential effects of MNS activity changes associated with kinematic differences between visual stimuli. Notably, motor evoked potentials, that reflect CSE, from the first dorsal interosseous muscle exhibited greater amplitude when the participants observed interactive behaviors than when they observed non-interactive behavior. These results provide neurophysiological evidence that the MNS is activated to a greater degree during observation of human-interactive behaviors that contain additional information about the individuals' mental states, supporting the view that the MNS plays a critical role in social cognition in humans.
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan; Faculty of Medicine, Yamaguchi University, 1-1-1 Minamikogushi, Ube, Yamaguchi 755-8505, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Aihara
authors.affiliation: School of Health and Sport Sciences, Osaka University of Health and Sport Sciences, 1-1 Asashirodai, Kumatori-cho, Sennan-gun, Osaka 590-0496, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Mori
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kushiro
authors.affiliation: Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, 1-4 Yamadaoka, Suita, Osaka 565-0871, Japan; The Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan. Electronic address: s.uehara@nict.go.jp.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Uehara
mesh_terms: D000328:Adult; D004644:Emotions; D019054:Evoked Potentials, Motor / Q000502:physiology*; D006225:Hand / Q000502:physiology; D006801:Humans; D008297:Male; D059167:Mirror Neurons / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D012919:Social Behavior; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult
keywords: Action observation; Corticospinal excitability; Human-interactive behavior; Mirror neuron system; Social cognition; Transcranial magnetic stimulation