Abstract
The idea of retinal and ex-retinal sources of saccadic suppression has long been established in previous studies. However, how they are implemented in local circuit remains unknown. Researchers have suggested that saccadic suppression was probably achieved by contrast gain control, but this possibility has never been directly tested. In this study, we manipulated contrast gain control by contrast-adapting observers with sinusoidal gratings of different contrasts. Presaccadic and fixational contrast thresholds were measured and compared to give estimates of saccadic suppression at different adaptation states. Our results reconfirmed the selective saccadic suppression in achromatic condition, and further showed that, achromatic saccadic suppression diminished as contrast adaptation was accentuated, whereas no significant chromatic saccadic suppression was induced by greater contrast adaptation. Our data provided evidence for the involvement of contrast gain control in saccadic suppression in achromatic channel. We also discussed how the negative correlation between contrast adaptation and saccadic suppression could be interpreted with contrast gain control.
Highlights
Saccade is the fast switch between fixation points
We psychophysically examined the relationship between contrast adaptation and saccadic suppression
Our result shows that in achromatic condition, saccadic suppression decreases as the contrast adaptation level of visual system increases, while in chromatic condition, saccadic suppression is not significant at all adaptation contrasts and no consistent tendency was induced by increasing adaptation contrast
Summary
Saccade is the fast switch between fixation points. Human and non-human primates direct their attention by making frequent saccadic eye movements. Results from several psychophysical researches suggest that contrast gain control could be the possible mechanism underlying saccadic suppression. One study utilizing masking paradigm shows that saccade attenuated visual sensitivity at all mask levels by a constant factor, which is a divisive way of gain modulation typically demonstrated in contrast gain control [11]. Impulse response peaks faster during saccade than that in fixation for luminance modulation, consistent with the suggestion that saccadic suppression is mediated by contrast gain control [12]. By comparing the two contrast thresholds, we derive direct evidence for the influence of contrast adaptation on saccadic suppression and further explain the interaction with contrast gain
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