Protective effects of testing across misinformation formats in the household scene paradigm

Many studies have demonstrated retrieval-enhanced suggestibility (RES), in which taking an initial recall test after witnessing an event increases suggestibility to subsequent misinformation introduced via a narrative. Recently, however, initial testing has been found to have a protective effect against misinformation introduced via cued-recall questions. We examined whether misinformation format (narrative vs. cued-recall questions) yields a similar dissociation in a paradigm that, to date, has consistently yielded a protective effect of testing (PET). After studying photos of household scenes (e.g., kitchen), some participants took an initial recall test. After a 48-hr delay, items not presented in the scenes (e.g., knives/plates) were suggested either via narrative or questions. Regardless of the misinformation format, we found a PET on both initial-test-conditionalised free recall and source-monitoring tests. However, initial testing also yielded memory costs, such that suggested items reported on the initial test were likely to persist on a final recall test. Thus, initial testing can protect against suggestibility, but can also precipitate memory errors when intrusions emerge on an initial test.

Opposite effect of motivated forgetting on sleep spindles during stage 2 and slow wave sleep

Memories selectively benefit from sleep. In addition to the importance of the consolidation of relevant memories, the capacity to forget unwanted memories is also crucial. We investigated the effect of suppressing unwanted memories on electroencephalography activity of subsequent sleep using a motivated forgetting (MF) paradigm as compared with a control non-forgetting task. Subjects were randomly assigned to nap or no-nap groups. We used a modified version of the think/no-think paradigm with dominant number of no-think words cued to be forgotten and included only subjects capable of suppressing unwanted memories by performing an initial subject inclusion experiment. In both groups and conditions, the performance of the subjects in recalling the word pairs learned in the beginning of the day was evaluated in a final recall test. We found that both nap and no-nap groups recalled significantly less no-think words in the MF condition compared to the control condition. Moreover, for the nap group, in the MF compared to the control condition, spindle power and density increased during stage 2 (S2) whereas they decreased during slow wave sleep (SWS). Interestingly, recall performance of no-think words was negatively correlated with spindle power during S2 whereas it was positively correlated with spindle power during SWS. These results indicate that sleep spindles are sensitive to the previous MF experiences and suggest a differential role of sleep spindles during S2 and SWS in memory processing during sleep.