Processing of emotional reactivity and emotional memory over sleep

Abstract

Sleep enhances memories, particularly emotional memories. As such, it has been suggested that sleep deprivation may reduce posttraumatic stress disorder. This presumes that emotional memory consolidation is paralleled by a reduction in emotional reactivity, an association that has not yet been examined. In the present experiment, we used an incidental memory task in humans and obtained valence and arousal ratings during two sessions separated either by 12 h of daytime wake or 12 h including overnight sleep. Recognition accuracy was greater following sleep relative to wake for both negative and neutral pictures. While emotional reactivity to negative pictures was greatly reduced over wake, the negative emotional response was relatively preserved over sleep. Moreover, protection of emotional reactivity was associated with greater time in REM sleep. Recognition accuracy, however, was not associated with REM. Thus, we provide the first evidence that sleep enhances emotional memory while preserving emotional reactivity.

Figure 1.

Study design and memory task. A, There were four groups. For the Sleep and Wake groups, the Encoding and Recognition Phases were separated by 12 h. The Morning and Evening control groups performed these phases within a session, ∼45 min apart. B, The task was an incidental memory task. During the Encoding Phase, participants viewed 60 pictures and rated the valence and arousal of each picture. During the Recognition Phase, participants viewed 60 target pictures intermingled with 120 foil pictures. Following the presentation of each picture, participants rated valence and arousal and made a yes/no memory judgment.

Figure 2.

Performance and sleep physiology measures. A, Hit rate in Session 2. B, ΔValence was computed as the SAM Valence ratings for Session 2 minus SAM valence ratings for Session 1. C, ΔArousal was computed as the SAM Arousal rating for Session 2 minus SAM Arousal rating for Session 1 (error bars indicate SE). D, Relationship between REM and ΔValence was significant. The percentage of the third quarter of the night spent in REM (REM3%) negatively correlated with ΔValence for negative items.