Different neural substrates underlying directed forgetting for negative and neutral images: an event-related potential study

Abstract

The aim of this study was to investigate the different neural correlations of directed forgetting for emotionally negative and neutral images in 17 healthy individuals using event-related potentials (ERPs). Behavioral findings showed that the task yielded a robust directed forgetting effect for both neutral and negative images: more to-be-remembered than to-be-forgotten images were recognized. ERPs were recorded as participants viewed different valence images (negative/neutral) and were given different instructions, including remember (R) or forget (F) commands. Enhanced late parietal positive potentials were observed for negative images during image viewing. In the 200-300 ms time window, F instructions elicited a larger N2 than did R instructions and successful implementation of F instructions (F-miss) appeared more negative over the frontal region comparing with the unintentional forgetting (R-miss), suggesting that F instructions trigger a frontal mechanism to inhibit the processing of previously presented images. More important, F instructions following emotionally negative images elicited an enhanced frontal N2 effect than neutral images. This result suggests that forgetting negative stimuli is more laborious. In addition, within the 300-400 ms time window, R instructions elicited a larger P3 response than did F instructions and successful implementation of the R instructions (R-hit) appeared more positive than the unintentional remembering (F-hit) over the posterior scalp region. This posterior wave might reflect rehearsal and memory consolidation process.