Differential inhibition of chromatic and achromatic... : NeuroReport (original) (raw)
Neurophysiology
Differential inhibition of chromatic and achromatic perception by transcranial magnetic stimulation of the human visual cortex
Paulus, Walter1,2; Korinth, Stefan1; Wischer, Stephan1; Tergau, Frithjof1
1Department of Clinical Neurophysiology, University of Göttingen, D-37075 Göttingen, Germany
2Corresponding Author: Walter Paulus
ACKNOWLEDGEMENTS: The authors wish to thank Drs B. Lee, W. Singer and U. Ziemann for critical reading of the manuscript and Dr B. Lee for providing the colour photometer for calibration. Supported by BMBF 0311 467 l-1059
Received 2 February 1999; accepted 19 February 1999
Abstract
THE magnocellular visual pathway is devoted to low-contrast achromatic and motion perception whereas the parvocellular pathway deals with chromatic and high resolution spatial vision. To specifically separate perception mediated by these pathways we have used low-contrast Gaussian filtered black–white or coloured visual stimuli. By use of transcranial magnetic stimulation (TMS) over the visual cortex inhibition of magnocellular stimuli was achieved distinctly earlier by about 40 ms compared with parvocellular information. A nonspecific inhibition of all stimuli could be seen peaking at 75–90 ms, significantly higher for magnocellular stimuli. The particular vulnerability of magnocellular stimuli to TMS is correlated with distinct physiological properties of this pathway such as faster conduction velocity and non-linear stimulus encoding.
© 1999 Lippincott Williams & Wilkins, Inc.