Continuous flash suppression: Manual action affects eye movements but not the reported percept.

Diverse paradigms, including ambiguous stimuli and mental imagery, have suggested a shared representation between motor and perceptual domains. We examined the effects of manual action on ambiguous perception in a continuous flash suppression (CFS) experiment. Specifically, we asked participants to try to perceive a suppressed grating while rotating a manipulandum. In one condition, the grating's motion was fully controlled by the manipulandum movement; in another condition the coupling was weak; and in a third condition, no movement was executed. We found no effect of the movement condition on the subjectively reported visibility of the grating, which is in contrast to previous studies that allowed for more top-down influence. However, we did observe an effect on eye movements: the gain of the optokinetic nystagmus induced by the grating was modulated by its coupling to the manual movement. Our results (a) indicate that action-to-perception transfer can occur on different levels of perceptual organization, (b) demonstrate that CFS involves the shared representations between action and perception differently than paradigms used in earlier studies, and