Abstract
Background. Temporal attention is deployed at specific moments to prioritize relevant information, and temporal expectation is developed based on the probabilities of when events occur. Microsaccades, small fixational eye movements, serve as an online measure for cognitive processes. Microsaccades impair perception of brief stimuli, are suppressed with expectation, and are suppressed more so with temporal attention. Previous studies either focused solely on expectation or attention effects on microsaccades, although these two mechanisms interact at the behavioral and neural levels. Goal. To investigate how temporal attention and expectation jointly modulate oculomotor control dynamics to improve perception. Methods. Observers maintained fixation while performing a 2AFC orientation discrimination task. Two Gabors were presented sequentially at the fovea with a variable onset. A precue instructed participants to attend to the first, second, or both stimuli. A response cue at the end of the trial indicated the target observers had to discriminate. We manipulated temporal expectation via precision (within-session onset variability), and hazard rate (within-trial onset delay). The probability of stimulus onset peaked in the middle of the temporal window, therefore, stimuli could appear earlier, at, or later than the expected moment. Results. Microsaccade rates decreased before the stimulus onset, and more so with hazard rate. Temporal attention amplified this effect. Temporal attention pulled microsaccade inhibition and rebound to an earlier time point, regardless of precision. Although optimal pre-stimulus attentional inhibition was not possible under low precision, post-stimulus microsaccade rebound occurred sooner with temporal attention. Despite similar inhibition, rebound microsaccades had smaller amplitude when temporal precision was high, indicating a decoupling between inhibition and rebound, and suggesting expectations modulate oculomotor control even after stimulus offset. Conclusions. Temporal attention and expectation are distinct mechanisms that jointly modulate microsaccade timing to optimize visual processing.