Detection threshold for an orientation-texture-defined (OTD) test grat
ing was elevated after adapting to an OTD grating of high orientation
contrast. Threshold elevation was greatest for a test grating parallel
to the adapting grating, and fell to zero for a test grating perpendi
cular to the adapting grating. We conclude that the human visual syste
m contains an orientation-tuned neural mechanism sensitive to OTD form
, and propose a model for this mechanism. We further propose that orie
ntation discrimination for OTD bars and gratings is determined by the
relative activity of these filters for OTD form. (C) 1998 Elsevier Sci
ence Ltd. All rights reserved.