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Abstract

When a stimulus has two competing interpretations, perception tends to alternate over time: bistable perception. A special case hereof occurs when the two eyes receive differing information in the same retinal space, perception also alternates: binocular rivalry (BR). Functional magnetic resonance imaging (fMRI) studies have shown the right anterior intraparietal sulcus (IPS) as well as posterior superior parietal lobule (SPL) activated during perceptual transitions. However, the causal role of these regions remains unclear, as distinct transcranial magnetic stimulation (TMS) studies have reported either shortening or lengthening TMS effects on perceptual dominance durations. Reasons for these divergent results may lie in the use of different stimuli or of distinct TMS protocols. Here we tested effects of a single, inhibitory TMS protocol, continuous theta burst stimulation (cTBS), applied to the IPS, SPL, and vertex control on distinct classes of bistable perception in three separate samples of participants (total N = 52). In sample one we used structure from motion (SFM) bistable perception, in sample two BR between random dots that was either reported, unreported or unreportable, and in sample three both of the above stimuli as well as BR between flickering checkerboards. Contrary to our expectation, cTBS neither consistently affected dominance durations across the stimuli, test sites, nor samples. This null effect was supported by Bayes factors. In a last experiment we correlated participants’ cTBS induced change in BR dominance with the change in motor-evoked potentials (MEP) following cTBS to primary motor cortex. While MEP amplitude was reduced, corroborating the inhibitory effect of cTBS, we observed no correlation with the cTBS effect on BR. Given the comparably large N used in the present study, the replication of our null-finding across several classes of bi-stable stimuli, and the lack of correlation of cTBS effects between motor and parietal cortex, the present findings cast doubt on the efficacy of the cTBS protocol over parietal cortex and the generalisation of cTBS effects from motor to parietal cortex.