Con guration Saliency Revealed by Dichoptic Masking

Supra-threshold spatial integration was studied by testing the saliency of multi Gabor element conngurations in short duration binocular rivalry (dichoptic masking) conditions. Dichoptic presentations allows for a competition between spatially overlapping supra-threshold stimuli that involve non-overlapping receptive elds in the rst stage of visual ltering. Diierent spatial conngurations of Gabor patches (= = 0:12 deg) were presented to one eye (target) together with a bandpass noise presented to the other eye (mask). After a short rivalry period (120ms) in which a dominance of one eye was established, a probe (a randomly positioned small rectangle of reduced contrast in the target) was presented for additional detection period (80ms). Probe detection performance was measured (2AFC) by nding the mask contrast leading to 75% correct response. Results show that connguration saliency is consistently expressed as dominance in short duration binocular rivalry. We nd that textures of randomly oriented patches are more dominant than uniform textures where the eeect decreases and eventually reverses with decreasing of contrast. For supra-threshold contours, however, we nd that smooth collinear contours are more dominant than \jagged" ones, regardless of phase and contrast. These nd-ings suggest principles underlying early lateral integration mechanisms based on contrast dependent inhibitory and excitatory connections. This mechanism could be based on iso-orientation surround (2D) inhibition and collinear (1D) facilitation, with inhibition being more eeective at high contrasts.