The effects of motion and smooth pursuit eye movements on the visibility of chromatic stimuli

Abstract

Previous literature showed that a drifting inducer modulates the sensitivity of an achromatic target abutting the inducer when the eyes are steady. Additionally, it has been shown that the contrast sensitivity to stimuli changes during smooth pursuit eye movements. Here, we investigated the changes in chromatic contrast sensitivity during the smooth pursuit for abutting target gratings. In the first experiment, we established the changes in chromatic contrast sensitivity caused by the inducer’s motion during fixation. Experiment 2 established the modulation of chromatic contrast sensitivity during smooth pursuit for the isolated dynamic target gratings. Finally, Experiments 3A and 3B investigated the changes in chromatic contrast sensitivity caused by the inducer’s motion during smooth pursuit. Additionally, by using isoluminant and luminance-modulated chromatic gratings, all experiments investigated the interaction of chromatic and luminance signals to better understand where the observed effects are processed in the brain. The contrast sensitivity was measured with a 2AFC task using the method of constant stimuli. Observers reported whether a low contrast target grating appeared above or below the fixation point. Results revealed a phase-dependent motion-induced sensitivity modulation during fixation, a directional selective contrast sensitivity modulation for dynamic target gratings during the pursuit, and an interaction between motion direction and smooth pursuit for abutting dynamic gratings. The results are discussed in terms of the interaction between chromatic motion perception and smooth pursuit. Moreover, the potential neural substrates of this interaction are discussed.