Abstract
Binocular rivalry (BR) requires two non-fusible images independently shown to each eye, but monocular rivalry or pattern rivalry (PR) occurs with the same image presented to both eyes. Periods of alternation experienced during PR typically differ in the strength or clarity of the overlapping components, rather than the complete dominance or suppression of visibility during BR. In this study, we recorded subject’s perceptual reports (N = 48) and MEG brain activity (N=30) while viewing BR or PR. For BR, subjects viewed orthogonal gratings with red in one eye and green in the other. This was compared to a PR condition with identical overlapping red and green gratings, with intersections compatible with the perception of transparency, shown to both eyes (dioptic viewing). For both BR and PR, the red or green gratings always flickered at F1 = 5 or F2 = 6.7 Hz, respectively. This resulted in SSVEP tagging of both eye and stimulus for BR, and tagging of stimulus for PR. Psychophysical findings show that rivalry alternation is slower for PR than BR. Mean duration of dominant or mixed percepts for PR is ~1.5 or 2.5 sec, compared to ~1.8 or 1.1 sec for BR. In fact, BR transition probabilities (between red, green, or mixed) are suggestive of tristability; this is not the case for PR. Overall, individual differences for alternation rate in PR exist and are modestly predicted by BR alternation rates (r-values of 0.4-0.5). MEG data suggests that, for PR, stimulus tagging during perceptual alternations produces strong power at fundamental frequencies as well as substantially greater power at several intermodulation frequencies compared to untagged PR, or tagged BR. Current results illustrate how, in the absence of interocular competition, bistable perception still occurs, but with different dynamics and neural substrates.