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.