Alessandro Benedetto^1,2,3 (), Michele A. Cox^1,2, Jonathan D. Victor⁴, Michele Rucci^1,2; ¹Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY, USA, ²Center for Visual Science, University of Rochester, Rochester, NY, USA, ³Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy, ⁴Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, USA

The human eyes are never at rest. Incessant movement also occurs in the intervals between saccades, when fixational drifts move the stimulus across many receptors on the retina. These drifts continually modulate the visual signals to the retina, and a growing body of evidence shows that the visual system uses spatial information provided by the resulting luminance modulations. In this study, we combined electroencephalography with high-resolution eye-tracking and gaze-contingent display control to directly estimate the influences of ocular drift on cortical responses in human observers. Subjects (N=15) maintained fixation on a high-frequency (10 cycles/deg) full-screen grating (~37x21 deg) modulated at ~7 Hz. The stimulus was presented at maximum contrast and either viewed normally, with the retinal motion caused by fixational drifts, or under retinal stabilization. In this latter condition, the stimulus moved on the display according to the observer’s eye movements, so to remain immobile on the retina. In both conditions, as expected, temporal modulation of the stimulus evoked a steady-state potential at twice the stimulus frequency, which primarily reflects responses from early visual areas. Since the image motion caused by eye movements redistributes the power of the stimulus on the retina, the spectral density distribution of the visual input was narrower under retinal stabilization, with more power concentrated at 7 Hz. Yet the magnitude of the EEG response was reduced by approximately 17% under retinal stabilization compared to natural viewing (t(14)=2.97, p=0.010). The result indicates that the continuous motion of the retinal image during fixation enhances early visual responses, even when the input is already temporally modulated. The dissociation between input power and response magnitude suggests the involvement of mechanisms driven by visuomotor contingencies that modulate early visual responses.

Acknowledgements: This work was supported by National Institutes of Health grants EY018363, EY07977, P30 EY001319, and University of Florence (Progetti competitivi 2025-2026)