Configuration saliency revealed in short duration binocular rivalry

Supra-threshold spatial integration was studied by testing the saliency of multi-Gabor element configurations in short duration binocular rivalry (dic hoptic masking) conditions. Dichoptic presentations allow for a competition between spatially overlapping supra-threshold stimuli that involve non-ove rlapping monocular receptive fields in the first stage of visual filtering. Different spatial cofigurations of Gabor patches (sigma = lambda = 0.12 de grees) were presented to one eye (target) together with a bandpass noise pr esented to the other eye (mask). After a short rivalry period (120 ms) in w hich a dominance of one eye was established, a probe (a randomly positioned small rectangle of reduced contrast in the target) was presented for addit ional detection period (80 ms). Probe detection performance was measured (t wo-alternative-forced choice paradigm (2AFC)) by finding the mask contrast leading to 79% correct response. Results show that configuration saliency i s consistently expressed as dominance in short-duration binocular rivalry, with similar results obtained for longer durations (200 ms and continuous p resentations). We find that textures of high-contrast randomly oriented pat ches are more dominant than uniform textures where the effect decreases and eventually reverses with decreasing of contrast. For supra-threshold conto urs, however, we find that smooth collinear contours are more dominant than 'jagged' ones, regardless of phase and contrast. These findings suggest pr inciples underlying early lateral integration mechanisms based on contrast dependent inhibitory and excitatory connections. This mechanism could be ba sed on iso-orientation surround (2D) inhibition and collinear (1D) facilita tion, with inhibition being more effective at high contrasts. (C) 1998 Else vier Science Ltd. All rights reserved.