Binocular Cross-Orientation Suppression in the Cat's Striate Cortex.
Gary A. Walker, Izumi Ohzawa, Ralph D. Freeman.
Group in Vision Science, School of Optometry, University of California,
Berkeley, CA 94720-2020.
APStracts 4:240N, 1997.
ABSTRACT
When a cortical cell is activated by an optimal sinusoidal grating, its
response can be attenuated by a superimposed second grating, oriented
orthogonally to the optimal stimulus. This effect is known as cross-
orientation suppression (COS). In previous work, monocular characteristics
have been explored and interocular tests have been conducted in an attempt to
locate the origin of the suppression. In this study, we have recorded
extracellularly from cortical cells to investigate the binocular
characteristics of COS. Our hypothesis is that binocular disparity influences
the strength of the effect. Our results do not support this supposition. We
find that binocular COS is as strong as monocular COS, but disparity changes
are of no consequence. We also conducted interocular tests in which the
optimal grating and the orthogonal mask were seen by separate eyes. Although
most interocular effects were weak, they were present in almost every cell and
spanned a wide range of suppression strengths. We also tested the effect of
asynchronous presentation of optimal and orthogonal gratings. These temporal
offsets did not affect the strength of COS. We conclude that the suppressive
mechanism underlying COS is primarily monocular and acts prior to the
convergence of the two monocular streams.
Received 10 July 1997; accepted in final form 9 September 1997.
APS Manuscript Number J573-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 7 October 1997