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Yuan Zhang, Jing Chen; Saccadic Suppression on Color and Luminance: Evidence from SSVEPs. Journal of Vision 2021;21(9):1883. doi: https://doi.org/10.1167/jov.21.9.1883.
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Our eyes make saccadic eye movements several times per second to direct the high-resolution fovea toward objects of interest in the environment. During saccades, visual sensitivity is severely suppressed. Currently, there are inconsistent results on whether saccadic suppression occurs in the parvocellular visual pathway in neurophysiological and psychophysical studies. We recorded steady-state visually evoked potentials (SSVEPs) induced by flickering background stimuli (flickering rate = 7.5 Hz) during the execution of saccades (Chen, Valsecchi & Gegenfurtner, 2019, Journal of Neurophysiology). The stimuli were either color-defined (isoluminant) or luminance-defined. Across two experiments, we found reduced SSVEP responses at the time of saccades compared to fixation periods before saccades. More importantly, the reduction in SSVEPs was similar for color-defined and luminance-defined stimuli (Experiment 1: t(13)=-0.64, p=0.53, BF01=3.10; Experiment 2: t(10)=0.46, p=0.66, BF01=3.07 ). In Experiment 2, we also measured the perceptual performance by asking the observer to discriminate a change of contrast in the stimuli. The change was fixed at a level that gave 82% accuracy during stable fixation measured in a pre-test. At the time of saccades, the accuracy dropped to 78.8% and 69.9% for color-defined and luminance-defined stimuli, respectively. The reduction in perceptual performance was more pronounced for luminance than color, t(10)=-2.47, p=0.03. Therefore, saccades likely suppress both the magnocellular and parvocellular pathways similarly up to the early visual cortex (see also in Kleiser et al., 2004; Sylvester et al., 2005). Saccades, however, seem to affect their subsequent processes differently, which may give rise to different perceptual suppressions on color and luminance.
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