Unwanted memories, such as emotionally negative, can be intentionally suppressed through voluntary control in humans. Memory suppression is thought to be mediated by the interplay of a chain of neurocognitive processes. However, empirical data in support of this notion is lacking. Using high-temporal resolution event-related potential (ERP) technique, we investigated the time course of ERPs associated with suppression of negative and neutral memories in a Think/No-Think paradigm in young, healthy participants. Results showed that participants had greater difficulty in suppressing emotionally negative memories than neutral ones. ERPs and source analyses demonstrated that memory suppression processing for negative and neutral memories were generally associated with changes during early components of a time window of 70-260 ms, such as P1 and N2, mainly at the right inferior frontal gyrus and occipital lobe; suppression of aversive memories was associated with two major late ERP components between 380 and 800 ms, with significantly smaller later negativity (LN) but larger late parietal positivity (LPP), primarily at the right medial and superior frontal gyri. These results suggest that differences in early components may reflect early stages of suppression processing including visual awareness, attention reallocation, and executive processing. Differences in late components between suppression of aversive and neutral memories may reflect a process of down-regulating conscious recollection of memory representations supported by prefrontal and parietal networks. A less effective control of this process, as evidenced by smaller LN and larger LPP, may explain the fact that emotionally negative memories were harder to be suppressed. Altogether, these findings suggest that suppression of aversive memories requires down-regulation of late conscious recollection, which can be dissociated from early visual and attention processing in memory suppression.
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