The magnitude and time course of pre-saccadic foveal prediction depend on the conspicuity of the saccade target.

Abstract

We previously demonstrated that during the preparation of a saccadic eye movement, human observers anticipate defining features of the eye movement target in pre-saccadic foveal vision (Kroell and Rolfs, 2022). In this Research Advance, we show that the conspicuity of feature information at the saccade target location influences the magnitude and time course of foveal enhancement. Observers prepared a saccade to a peripheral orientation signal (the target) while monitoring the appearance of another orientation signal (the probe) in their pre-saccadic center of gaze. The foveal probe appeared in 50% of trials and either had the same orientation as the target (congruent) or a different orientation (incongruent). Crucially, we manipulated the opacity of the target against the 1/f noise background in four logarithmic steps (25-90%). An increase in opacity translated to an increase in luminance contrast and signal-to-noise ratio of orientation information within the target region. Foveal enhancement defined as the difference between hit rates to target-congruent and target-incongruent foveal probes increased with target opacity. Moreover, the time course of foveal enhancement showed an oscillatory pattern that was particularly pronounced at high target opacities. Reverse correlations furthermore suggest that at higher target opacities, false alarms were increasingly triggered by signal, i.e., by incidental orientation information in the foveal noise. Beyond providing new mechanistic insights, these findings are relevant for researchers planning to adapt our paradigm to study related questions. Presenting the saccade target at a high signal-to-noise ratio appears beneficial, as foveal congruency effects, especially when time-resolved, are most robustly detectable.