Retinal and extra-retinal contributions of blinking to perceptual alternation in bistable apparent motion

Blinks serve not only to maintain ocular lubrication, but may also contribute to visual processing, although their functional role remains poorly understood. Recent research has shown that spontaneous and voluntary blinks serve distinct functions in perceptual competition involving binocular interactions (Sato & Kimura, 2024). To disentangle the retinal and extra-retinal contributions of blinking, this study investigated how different types of blinks affect perceptual alternation using a bistable apparent motion stimulus where the perceived motion direction alternates between vertical and horizontal. Results showed that instructed (i.e., voluntary) blinks facilitated perceptual alternation, whereas spontaneous blinks did not. The time to perceptual alternation was longer on spontaneous-blink trials, but these blinks showed no clear temporal association with the alternation. Physical blackouts simulating blinks also did not affect perceptual alternation. However, these same blackouts did modulate it when susceptibility to perceptual alternation was high, suggesting that retinal transients have a limited but condition-dependent effect. Moreover, the lack of modulation from instructed key presses suggests that extra-retinal self-motion signals per se cannot account for the effect. Notably, instructed eye widenings, which do not involve eyelid closure, also facilitated perceptual alternation. Taken together, these results suggest that the facilitatory effects of voluntary blinking primarily reflect extra-retinal signals associated with voluntary eyelid movements.