Assimilation of optic flow in saccadic eye movements

When executing a saccade during locomotion, the position of the saccade target changes during the movement. Ideally, our visual system should adjust the saccade parameters to compensate for the different optic flow fields. We asked how optic flow affects the parameters of saccades to stationary targets, a question that has not been fully answered. The results showed a strong assimilation effect of optic flow, such that saccade amplitudes were biased in the direction of the optic flow. We estimated that between 13% to 25% of optic flow was assimilated. Moreover, saccade latencies were shorter in optic flow fields. These findings indicate that the oculomotor system partially accounts for the expected displacement due to optic flow in the planning of saccadic eye movements, and are consistent with the assimilation of background motion in smooth pursuit eye movements.