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Lisa M. Kroell, Martin Rolfs; Predictive enhancement of saccade target features in the pre-saccadic center of gaze. Journal of Vision 2021;21(9):1889. doi: https://doi.org/10.1167/jov.21.9.1889.
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While pre-saccadic sensitivity modulations at the target of an eye movement have been studied extensively, little is known about the concurrent development of visual sensitivity in the center of gaze. Using a dynamic noise paradigm, we demonstrate that defining features of an upcoming saccade target predictively alter foveal perception. We asked observers to detect an orientation-filtered pink noise patch (the probe; presented on 50% of trials) in their center of gaze while they prepared a saccade to another orientation-filtered patch (the target). Probe and target exhibited one of two possible orientations, such that the probe was oriented either congruently or incongruently to the target. Both stimuli were smoothly embedded in a stream of pink noise images covering the entire screen. We found that foveal hit rates decreased continuously during saccade preparation, when attention is known to shift to the target. Crucially, this decrease was less pronounced for target-congruent than for target-incongruent probes starting 200 ms before saccade onset. When generating a false alarm (FA), observers reported perceiving target-congruent probes more often than incongruent ones. Reverse correlations revealed that FAs were by no means unsystematic but relied on an incidental, high energy of the reported orientation in the foveal noise region. Notably, for observers to perceive a target-incongruent probe in the foveal noise, strong and unambiguous evidence for its orientation was required. Weaker foveal evidence for the target orientation was sufficient to trigger congruent FAs. These correlations between noise content and response behavior were specific to the foveal noise region. Combined, our results demonstrate that, during saccade preparation, sensitivity to target-congruent features increases in the very center of gaze. To our knowledge, this constitutes the first behavioral evidence for a predictive, foveal sensitization to soon-to-be fixated features—a mechanism that may support the continuous perception of saccade targets across eye-movement-induced displacements.
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