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Neural dynamics of retrieval suppression in abolishing item-specific cortical pattern of unwanted emotional memories

When reminded of an unpleasant experience, people often try to exclude the unwanted memory from awareness in an effort to forget it, a process known as retrieval suppression. Yet, how fast can individual memories be targeted and controlled, and the neural dynamics in modulating item-specific cortical traces, remain elusive. Here, using multivariate decoding analyses on time-domain and time-frequency-domain EEGs, we found that retrieval suppression of aversive memories was distinct from retrieval and passive viewing, when given a reminder. Specifically, early elevation of mid-frontal theta power during the first 500 ms distinguished retrieval suppression from passive viewing, suggesting that suppression recruited early active control processes. On an item-level, we could discern activities relating to individual memories during active retrieval - initially, based on perceptual responses to reminders (0-500 ms) and later, via the reinstatement and maintenance of the target aversive scenes (500-3000 ms). Critically, suppressing retrieval significantly weakened (during 420-600 ms) and eventually abolished these item-specific cortical patterns till cue disappeared (1200-3000 ms), suggesting the successful exclusion of the unwelcome memory from awareness. Suppression of item-specific cortical patterns, particularly during an early 300-680 ms time window, bore behavioral consequences in predicting subsequent episodic forgetting. These findings present a precise timeline on the suppression of specific unwelcome memories: upon perceiving an unwelcome reminder, people rapidly deploy inhibitory control to truncate retrieval within 500 ms, which likely terminate the reminder-to-memory conversion at around 500 ms that would ordinarily arise through hippocampal pattern completion. We concluded that both rapid and sustained control are critical in abolishing cortical patterns of individual memories, limiting unwelcome awareness, and precipitating later forgetting.