During binocular rivalry, perception is bistable in that observers perceive only one of two monocular stimuli, with perception inevitably switching to the other stimulus after some variable duration. A related form of bistability occurs when dissimilar stimuli (still presented one to each eye) are swapped rapidly between the eyes— a phenomenon commonly termed stimulus rivalry.

Here, we report that transcranial magnetic stimulation (TMS) of early visual areas perturbs the dynamics of binocular rivalry while having no measurable effect on stimulus rivalry. The location of the TMS coil was adjusted until observers reported a phosphene overlapping the subsequent stimulus area. A single TMS pulse was delivered every 3.2 s while observers tracked perceptual alternations during rivalry. TMS increased the probability of experiencing binocular rivalry alternations ~ 0.75 s after the TMS pulse. When we applied TMS at a location eliciting peripheral phosphenes, we found only a weak effect, indicating retinotopic specificity of the interaction between TMS and binocular rivalry. Stimulus rivalry, however, was unaffected by TMS stimulation, indicating that these two seemingly related dynamical processes differ in their neural bases. In addition, the effect of TMS on the duration of a binocular rivalry state was proportional to the length of time an observer had been in that state.

Hence, rather than merely inducing a temporary lesion, the effect of TMS was retinotopically specific and proportional to the time course of binocular rivalry or the brain state at any given instant.

Supported by NIH EY13358 (RB).