Temporal expectations modulate face image repetition suppression of early stimulus evoked event-related potentials.

Repeated exposure to a stimulus leads to reduced responses of stimulus-selective sensory neurons, an effect known as repetition suppression or stimulus-specific adaptation. Several influential models have been proposed to explain repetition suppression within hierarchically-organised sensory systems, with each specifying different mechanisms underlying repetition effects. We manipulated temporal expectations within a face repetition experiment to test a critical prediction of the predictive coding model of repetition suppression: that repetition effects will be larger following stimuli that appear at expected times compared to stimuli that appear at unexpected times. We recorded event-related potentials from 18 participants and mapped the spatiotemporal progression of repetition effects using mass univariate analyses. We then assessed whether the magnitudes of observed face image repetition effects were influenced by temporal expectations. In each trial participants saw an adapter face, followed by a 500 ms or 1000 ms interstimulus interval (ISI), and then a test face, which was the same or a different face identity to the adapter. Participants' expectations for whether the test face would appear after a 500 ms ISI were cued by the sex of the adapter face. Our analyses revealed multiple repetition effects with distinct scalp topographies, extending until at least 800 ms from stimulus onset. An early (158-203 ms) repetition effect was larger for stimuli following surprising, rather than expected, 500 ms ISI durations, contrary to the model predictions of the predictive coding model of repetition suppression. During this time window temporal expectation effects were larger for alternating, compared to repeated, test stimuli. Statistically significant temporal expectation by stimulus repetition interactions were not found for later (230-609 ms) time windows. Our results provide further evidence that repetition suppression can reduce neural effects of expectation and surprise, indicating that there are multiple interactive mechanisms supporting sensory predictions within the visual hierarchy.