Abstract
Much work has been dedicated to the spatial consequences of eye movements, i.e., how gaze shifts position the stimulus on the retina. In contrast, considerably less attention has been paid to the temporal consequences of oculomotor activity, i.e., the possible impact of the luminance changes that eye movements produce on the retina. A growing body of evidence supports the notion that oculomotor modulations are functionally important, and that the visual system use them to establish a temporal scheme of spatial encoding. Here we focus on the commonalities in the modulations resulting from different types of eye movements. Can a single framework characterize modulations from eye movements as diverse as the fast and rapid saccades and the slow and small eye drifts of visual fixation? To investigate this question, we recorded the human eye movements at high-resolution, reconstructed the spatiotemporal input signals impinging onto retinal receptors, and examined how different types of eye movements transform the spatial power of the scene into temporal modulations on the retina. We show that very different types of eye movements yield luminance flows on the retina with qualitatively similar spectral distributions. The power redistribution can always be decomposed into two regimes:a whitening regime below a critical spatial frequency, in which the amount of stimulus power transformed into temporal modulation grows proportionally to spatial frequency; and a saturation regime, above this critical frequency, in which the temporal power available is a constant fraction of the stimulus’ spatial power, independent of spatial frequency. The critical spatial frequency varies across eye movements: it is highest for drift, lower for saccades, and decreases with saccade amplitude. These results reveal a continuum in the modulations given by different eye movements. Transitions across eye movements primarily act by shifting the boundaries between whitening and saturation regimes on the retina.
Acknowledgement: NIH grants EY018363 and EY07977 NSF grants BCS-1457238 and 1420212