Timing of activity in early visual cortex as revealed by transcranial magnetic stimulation.

To determine the timing of visual processing in the early visual cortex, we applied single pulse transcranial magnetic stimulation to the occipital pole of healthy subjects while they were engaged in a forced-choice visual letter-identification task. We found two separate periods of activity, the first ranging from 20 to 60 ms after the onset of the visual stimulus, and the second ranging from 100 to 140 ms after the onset of the visual stimulus. We suggest that these two periods reflect necessary activity in V1, before and after re-entry.

[1]  A. Cowey.  PROJECTION OF THE RETINA ON TO STRIATE AND PRESTRIATE CORTEX IN THE SQUIRREL MONKEY, SAIMIRI SCIUREUS. , 1964, Journal of neurophysiology.

[2]  M. Livingstone,et al.  Neuronal correlates of visibility and invisibility in the primate visual system , 1998, Nature Neuroscience.

[3]  John H. R. Maunsell,et al.  Visual response latencies in striate cortex of the macaque monkey. , 1992, Journal of neurophysiology.

[4]  M. Tovée,et al.  Processing speed in the cerebral cortex and the neurophysiology of visual masking , 1994, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[5]  H. Masur,et al.  Suppression of visual perception by transcranial magnetic stimulation--experimental findings in healthy subjects and patients with optic neuritis. , 1993, Electroencephalography and clinical neurophysiology.

[6]  V. Hömberg,et al.  Cerebral visual motion blindness: transitory akinetopsia induced by transcranial magnetic stimulation of human area V5 , 1992, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[7]  G Kovács,et al.  Cortical correlate of pattern backward masking. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[8]  Bruce Bridgeman,et al.  Correlates of metacontrast in single cells of the cat visual system , 1975, Vision Research.

[9]  U. Ziemann,et al.  Transient visual field defects induced by transcranial magnetic stimulation over human occipital pole , 1998, Experimental Brain Research.

[10]  S. Zeki,et al.  The consequences of inactivating areas V1 and V5 on visual motion perception. , 1995, Brain : a journal of neurology.

[11]  D. V. van Essen,et al.  Neuronal responses to static texture patterns in area V1 of the alert macaque monkey. , 1992, Journal of neurophysiology.

[12]  C M Epstein,et al.  Magnetic coil suppression of extrafoveal visual perception using disappearance targets. , 1996, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[13]  G. Orban,et al.  How well do response changes of striate neurons signal differences in orientation: a study in the discriminating monkey , 1990, The Journal of neuroscience : the official journal of the Society for Neuroscience.