Napping and the selective consolidation of negative aspects of scenes

Abstract

After information is encoded into memory, it undergoes an offline period of consolidation that occurs optimally during sleep. The consolidation process not only solidifies memories, but also selectively preserves aspects of experience that are emotionally salient and relevant for future use. Here, we provide evidence that an afternoon nap is sufficient to trigger preferential memory for emotional information contained in complex scenes. Selective memory for negative emotional information was enhanced after a nap compared with wakefulness in 2 control conditions designed to carefully address interference and time-of-day confounds. Although prior evidence has connected negative emotional memory formation to REM sleep physiology, we found that non-REM delta activity and the amount of slow wave sleep (SWS) in the nap were robustly related to the selective consolidation of negative information. These findings suggest that the mechanisms underlying memory consolidation benefits associated with napping and nighttime sleep are not always the same. Finally, we provide preliminary evidence that the magnitude of the emotional memory benefit conferred by sleep is equivalent following a nap and a full night of sleep, suggesting that selective emotional remembering can be economically achieved by taking a nap.

Figure 1

A. Experimental design for the Nap group and two Wake control groups (Wake1 and Wake2). B. Experimental design of our prior overnight study, for purposes of comparison. Note different time scale.

Figure 2

A. Sample Stimuli. Sample stimuli with a neutral background and either a neutral object (intact car) or negative object (crashed car) in the foreground. B. A nap selectively benefits memory for emotional components of scenes. This figure depicts mean general recognition memory for objects and backgrounds in the nap and combined wake groups. Separate graphs show results for negative scenes (left), and neutral scenes (right). The arrow highlights the benefit conferred selectively to negative objects following the nap compared to wakefulness. Note, however, that no such differences emerge for the backgrounds on which these negative objects are embedded, or for either component (objects or backgrounds) of neutral scenes. Significant differences are denoted by asterisks, *p<.05

Figure 3

Mean recognition memory for emotional objects and paired neutral backgrounds in the overnight sleep group from Payne et al (2012b) compared to the daytime nap group from the current study. Dashed arrows denote the magnitude of the trade-off effect, which is statistically equivalent between groups.

Figure 4

Correlations of SWS and delta power with general recognition memory