Dependence of perceptual saccadic suppression on peri-saccadic image flow properties and luminance contrast polarity

Abstract

Perceptual detectability of brief visual stimuli is strongly diminished across saccades. Recent work showed that this perceptual suppression phenomenon is jumpstarted in the retina (Idrees et al., 2020), suggesting that the phenomenon might be significantly more visual in nature than normally acknowledged. Here, we explored the details of visual-visual interactions underlying saccadic suppression, and we did so by comparing suppression strength when saccades were made across a uniform image of constant luminance versus when saccades were made across image patches of different luminance, width, and trans-saccadic luminance polarity. In 6 human subjects, we measured perceptual contrast thresholds for brief peri-saccadic flashes of positive (luminance increments) or negative (luminance decrements) polarity. In different conditions, gaze crossed a luminance edge or stripe before landing on a uniform background like in the control condition. Perceptual thresholds were >6-7 times higher when saccades translated a luminance stripe or edge across the retina than when the movements were made over a completely uniform image patch. Moreover, both background luminance and flash luminance polarity relative to the background strongly modulated peri-saccadic contrast thresholds: dark backgrounds were associated with the strongest suppression, and negative polarity flashes over dark backgrounds caused stronger suppression than positive polarity flashes over the same backgrounds. Most importantly, we repeated the same experiments on all subjects with rapid image translations (simulating saccadic visual flows on the retina) without any real saccades. All of the image dependencies that we observed with real saccades (e.g. suppression with gaze crossing an edge or stripe versus suppression with a uniform background) also occurred. Our results indicate that perceptual saccadic suppression may be fundamentally a visual phenomenon. They also strongly motivate revisiting both the movement-related and visual components of saccadic suppression, and investigating how saccade movement commands may interact with visual-visual interactions in shaping trans-saccadic visual perception.