title: Optimum stimulus size for the human brain to respond to motion: a magnetoencephalographic study.
abstract: OBJECTIVE
  To determine if there is an optimum spatial extent for the detection of moving objects in humans.
  
  
  METHODS
  We investigated human brain responses to motion at various speeds (2.9-23.5 deg/s) and stimulus sizes (2.2 × 2.9 deg to 44.8 × 57.4 deg) using magnetoencephalography. The results were compared with those for the flickers with the same stimulus sizes and temporal frequencies.
  
  
  RESULTS
  For every size, response latency was inversely related to speed. Further, the latency was lowest at a stimulus size of 16.8 × 22.4 deg for every speed. Although response latency was inversely related to the temporal frequency of the flicker stimulation for all stimulus sizes, it was not affected by stimulus size as much as motion stimulus.
  
  
  CONCLUSIONS
  For visual motion detection, the most efficient stimulus size is around 16.8 × 22.4 deg.
  
  
  CONCLUSIONS
  The results suggest that spatial summation mechanism is important for the detection of visual motion but a loss of reference frame information affects the detection of larger motion stimuli, supporting the view that illusory self-motion (vection) is caused by poor reference frame information for motion detection.
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji-cho, Okazaki 444-8585, Japan. turakawa@nips.ac.jp
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Urakawa
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kaneoke
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000704:Analysis of Variance; D001703:Biophysics; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods / Q000592:standards; D008297:Male; D008875:Middle Aged; D009038:Motion; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology