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The consequences of inactivating areas V1 and V5 on visual motion perception

G. Beckers, S. Zeki
DOI: http://dx.doi.org/10.1093/brain/118.1.49 49-60 First published online: 1 February 1995

Summary

Summary We studied the capacity of normal humans to discriminate the direction of motion of visual stimuli when areas VI or V5 were reversibly inactivated with transcranial magnetic stimulation. We found that (i) magnetic stimulation of V5 at intervals of −20 to +10 ms before or after the onset of visual stimulation was effective in abolishing motion perception—other delays were not; (ii) magnetic stimulation of VI abolished motion perception only marginally and at delays which were significantly different from those obtained with V5, the stimulation now being effective only at delays of 60–70 ms after the onset of visual stimulation. We conclude (i) that stimulation of V5 is a much more potent way of inducing akinetopsia (motion imperception) than stimulation of VI ; (ii) that perceptually effective visual motion signals reach V5 at or before 30 ms and reach VI at or before 60 ms— consequently, perceptually effective motion signals reach V5 before they reach VI ; (iii) that, given the time course of arrival of signals in VI and V5, it takes about 30–50 ms for signals from VI to reach V5. We conclude further that there are probably two components reaching V5 from the retina, a fast one which bypasses VI and a slow one which reaches it through VI.

  • area VI
  • area V5
  • visual motion perception
  • residual motion vision
  • akinetopsia
  • parallel visual input
  • transcranial magnetic stimulation (TMS)