Orientation-Specific Inhibitory Plasticity in Binocular Rivalry

Purpose: During binocular rivalry, the proportion of exclusive percepts typically declines gradually. This study investigated whether this plasticity arises from orientation-specific weakening of interocular suppression and explores its underlying neural computational mechanisms. Methods: Participants performed binocular rivalry tests interleaved with interocular suppression measurements, during which a monocular probe was detected against a suppressive pedestal to estimate detection thresholds. In Experiments 1 and 2, interocular suppression strength was tracked over the course of binocular rivalry. In addition, in Experiment 3, binocular fusion rings were introduced during the detection task to attenuate interocular suppression. Furthermore, a neural computational model incorporating anti-Hebbian plasticity in orientation-tuned interocular inhibitory connections was used to simulate the empirical results and elucidate the underlying mechanism. Results: Psychophysical results showed a progressive decrease in perceptual exclusivity during binocular rivalry. Interocular suppression exhibited orientation-specific weakening: suppression decreased when stimulus orientations were matched between the rivalry and detection tasks (congruent condition), but not when orientations differed (incongruent condition) or when suppression was eliminated. Across participants, decreases in perceptual exclusivity were positively correlated with reductions in interocular suppression exclusively in the congruent condition. The computational model successfully reproduced these results, indicating that orientation-selective modification of inhibitory connections via anti-Hebbian learning accounts for the observed plasticity. Conclusions: These findings suggest that rivalry-induced plasticity may arise from orientation-specific weakening of interocular suppression, mediated by anti-Hebbian plasticity at inhibitory synapses. This work provides a mechanistic framework for understanding experience-dependent short-term binocular plasticity in the adult visual system.