Modulation of binocular rivalry with rapid monocular visual stimulation.

Rapid visual stimulation can increase synaptic efficacy by repeated synaptic activation. This long-term potentiation-like (LTP-like) effect can induce increased excitability in the human visual cortex. To examine the effect of rapid visual stimulation on perception, we tested the hypothesis that rapid monocular visual stimulation would increase the dominance of the stimulated eye in a binocular rivalry task. Participants (n = 25) viewed orthogonal 0.5 cpd gratings presented in a dichoptic anaglyph to induce binocular rivalry. Rivalry dynamics (alternation rate, dominance, and piecemeal durations) were recorded before and after 2 min of rapid monocular stimulation (9 Hz flicker of one grating) or a binocular control condition (9 Hz alternation of the orthogonal gratings viewed binocularly). Rapid monocular stimulation did not affect alternation rates or piecemeal percept duration. Unexpectedly, the rivalry dominance of the stimulated eye was significantly reduced. A further experiment revealed that this effect could not be explained by monocular adaptation. Together, the results suggest that rapid monocular stimulation boosts dominance in the non-stimulated eye, possibly by activating homeostatic interocular gain control mechanisms.