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

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.