“Repulsive-followed-by-attractive” past-present neural interactions underlie serial dependence

Current perception tends to be spontaneously influenced by the previous trial, namely serial dependence. This has been posited to arise from a perceptual temporal continuity field or a two-stage process. Hence, examining how past reactivation interacts with current information throughout various stages within each trial, i.e., encoding and decision-making, is essential to tackling the question. Here we performed two spatial perception tasks with electroencephalography (EEG) and magnetoencephalography (MEG) recordings. In Experiment 1, participants memorized the location of a dot within a 2-D continuous space (encoding stage) and reproduced it later (decision-making stage). In Experiment 2 with attentional modulation added, participants memorized locations of two dots and recalled the cued dot location later. Behaviorally, both experiments showed attractive serial bias, i.e., spatial perception is biased toward the previously reported location. Importantly, past-trial reactivation co-occurs with current-trial information during both the encoding and decision-making stages, signifying past-present interactions. Most interestingly, the past-present neural interactions exhibit a two-stage dynamic profile: repulsive interactions during encoding and attractive interactions during decision-making, arising in the visual cortex and orbitofrontal cortex (OFC), respectively. Finally, only the late attractive interaction is modulated by attention and correlates with serial bias behavior, while the early repulsive interaction is task-irrelevant. Overall, our study provides novel neural evidence supporting that serial dependence involves a repulsive-followed-by-attractive two-stage process, wherein past information first repulses present processing during sensory encoding in a task-irrelevant way and is then integrated with it in OFC based on task modulation during decision-making.