Residual Foveal Motion Facilitates Processing of Visually Tracked Objects.

Humans and other species visually track moving objects via pursuit eye movements. These movements fail to stabilize the stimulus on the retina, an effect often attributed to errors in oculomotor control. However, it remains unclear whether the resulting residual retinal motion serves visual functions. Using high-resolution eye tracking, we reconstructed foveal motion during discrimination of both stationary and moving stimuli. We show that the retinal motion elicited by pursuit is heavily constrained and strikingly mirrors the motion present during normal active fixation. We then show that this motion performs an important information-compression computational function by equalizing luminance modulations in a low-spatial-frequency range during tracking of natural stimuli. Finally, we show that the resulting visual signals during tracking contribute to perceptual judgments, shifting spatial sensitivity toward lower frequencies relative to fixation. These results suggest that retinal motion during pursuit constitutes an active strategy for encoding space in the joint space-time domain.