Slow rhythmic eye motion predicts periodic alternation of bistable perception

Bistable perception is characterized by periodic alternation between two different perceptual interpretations, the mechanism of which is poorly understood. Herein, we show that perceptual decisions in bistable perception are strongly correlated with slow rhythmic eye motion, the frequency of which varies across individuals. From eye gaze trajectory measurements during three types of bistable tasks, we found that each subjects gaze position oscillates slowly(less than 1Hz), and that this frequency matches that of bistable perceptual alternation. Notably, the motion of the eye apparently moves in opposite directions before two opposite perceptual decisions, and this enables the prediction of the timing and direction of perceptual alternation from eye motion. We also found that the correlation between eye movement and a perceptual decision is maintained during variations of the alternation frequency by the intentional switching or retaining of perceived states. This result suggests that periodic bistable perception is phase-locked with rhythmic eye motion.