Two distinct modes of ocular drift observed during figure-ground perception

Precise coordination between neurons and cortical areas is crucial for sensory perception, yet in vision, continuous fixational eye movements constantly shift retinal input. Traditionally considered random, these drifts modulate neural activity and may challenge the temporal precision needed for perceptual integration, particularly given their partial interocular independence. Recent evidence suggests that ocular drifts are not purely stochastic and play an active role in visual processing. Here, we investigated the impact of fixational eye movements on visual perception using a figure-ground segmentation task. Participants maintained central fixation while viewing textures composed of oriented line segments and reported the presence or absence of a centrally embedded figure. We simultaneously recorded binocular drift and microsaccades, analyzing interocular coordination through 2D cross-correlograms of angular velocities. We found that figure-presents trials exhibited narrow peaks in interocular correlation, while figure-absent trials showed broader, less synchronized drift patterns. Microsaccades were observed to facilitate drift alignment across the eyes. The decrease in microsaccade rate in figure-present trials may contribute to the change in drift synchrony, but it is not required for it. Changes in eye synchrony are also observed under monocular viewing conditions, whereas variations in accommodation and pupil size appear to be unrelated. These results identify two distinct ocular drift modes associated with different perceptual outcomes. Our findings suggest that ocular drift operates under closed-loop control and contributes to effective visual processing.