Orientation-tuned spatial filters for texture-defined form

Detection threshold for an orientation-texture-defined (OTD) test grating 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 perpendicular to the adapting grating. We conclude that the human visual system contains an orientation-tuned neural mechanism sensitive to OTD form, and propose a model for this mechanism. We further propose that orientation discrimination for OTD bars and gratings is determined by the relative activity of these filters for OTD form. (C) 1998 Elsevier Science Ltd. All rights reserved.