title: Differential orientation effect in the neural response to interacting biological motion of two agents.
abstract: BACKGROUND
  A recent behavioral study demonstrated that the meaningful interaction of two agents enhances the detection sensitivity of biological motion (BM), however, it remains unclear when and how the 'interaction' information of two agents is represented in our neural system. To clarify this point, we used magnetoencephalography and introduced a novel experimental technique to extract a neuromagnetic response relating to two-agent BM perception. We then investigated how this response was modulated by the interaction of two agents. In the present experiment, we presented two kinds of visual stimuli (interacting and non-interacting BM) with two orientations (upright and inverted).
  
  
  RESULTS
  We found a neuromagnetic response in the bilateral occipitotemporal region, on average 300 - 400 ms after the onset of a two-agent BM stimulus. This result showed that interhemispheric differences were apparent for the peak amplitudes. For the left hemisphere, the orientation effect was manifest when the two agents were made to interact, and the interaction effect was manifest when the stimulus was inverted. In the right hemisphere, the main effects of both orientation and interaction were significant, suggesting that the peak amplitude was attenuated when the visual stimulus was inverted or made to interact.
  
  
  CONCLUSIONS
  These results demonstrate that the 'interaction' information of two agents can affect the neural activities in the bilateral occipitotemporal region, on average 300 - 400 ms after the onset of a two-agent BM stimulus, however, the modulation was different between hemispheres: the left hemisphere is more concerned with dynamics, whereas the right hemisphere is more concerned with form information.
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki, Japan. hirai@nips.ac.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hirai
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002540:Cerebral Cortex / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007398:Interpersonal Relations; D015225:Magnetoencephalography; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D019370:Observation; D009949:Orientation; D010775:Photic Stimulation / Q000379:methods; D012016:Reference Values; D013997:Time Factors; D014795:Visual Pathways / Q000502:physiology*