REM-Enriched Naps Are Associated with Memory Consolidation for Sad Stories and Enhance Mood-Related Reactivity

Abstract

Emerging evidence suggests that emotion and affect modulate the relation between sleep and cognition. In the present study, we investigated the role of rapid-eye movement (REM) sleep in mood regulation and memory consolidation for sad stories. In a counterbalanced design, participants (n = 24) listened to either a neutral or a sad story during two sessions, spaced one week apart. After listening to the story, half of the participants had a short (45 min) morning nap. The other half had a long (90 min) morning nap, richer in REM and N2 sleep. Story recall, mood evolution and changes in emotional response to the re-exposure to the story were assessed after the nap. Although recall performance was similar for sad and neutral stories irrespective of nap duration, sleep measures were correlated with recall performance in the sad story condition only. After the long nap, REM sleep density positively correlated with retrieval performance, while re-exposure to the sad story led to diminished mood and increased skin conductance levels. Our results suggest that REM sleep may not only be associated with the consolidation of intrinsically sad material, but also enhances mood reactivity, at least on the short term.

The ‘affect tagging and consolidation’ (ATaC) model of depression vulnerability

“…Studies in healthy participants demonstrate that both REM sleep density and REM sleep duration during the consolidation interval following encoding of emotional and neutral stimuli correlates positively with memory performance for negative but not neutral stimuli (Gilson et al, 2015;Nishida, Pearsall, Buckner, & Walker, 2009;Payne, Chambers, & Kensinger, 2012). These findings support the notion that REM sleep plays a selective role in the consolidation of negative emotional memories (Goldstein & Walker, 2014;Walker & van der Helm, 2009).…”

“…Nonetheless, a recent study by Gilson and colleagues (2015) reports that in healthy participants greater REM sleep density during a 90-minute morning nap was associated with greater recall performance for sad emotional stories, but not neutral stories (Gilson et al, 2015). Human neuroimaging studies reveal that rapid eye movements (REMs) during REM sleep are closely associated with transient activity in limbic regions such as the amygdala and parahippocampal gyrus (Abe, Ogawa, Nittono, & Hori, 2004;Ioannides et al, 2004).…”

“…Research which demonstrates that many compounds with antidepressant properties suppress REM sleep (Mayers & Baldwin, 2005;Steiger & Kimura, 2010; also see: Murck et al, 2003;Nofzinger et al, 1995;Sonntag et al, 1996), considered alongside evidence that REM sleep duration and density is associated with the consolidation of negative memories (Gilson et al, 2015;Groch et al, 2015;Nishida et al, 2009;Payne et al, 2012;Wagner et al, 2001;Wiesner et al, 2015), has led researchers to speculate that REM sleep alterations may underlie the emotional memory bias observed in depressed patients (Walker & van der Helm, 2009;Walker, 2009). However, the majority of studies directly investigating the effect of REM sleep on emotional memory consolidation focus exclusively on comparisons between recognition performance for neutral and negatively salient stimuli (however see : Cairney, Durrant, Power, & Lewis, 2015), ignoring the possibility that REM sleep may also play a role in the consolidation of positive memories.…”

Sleep to Remember

“…This study is still highly cited as evidence for a dissociation of the roles of REM and NREM sleep in procedural and declarative memory, respectively. Subsequent supporting evidence is sparse, with Genzel et al (2009) Evidence for a role of REM sleep in consolidation of the emotional components of memories is stronger, with several recently published studies in humans (for review, see Gilson et al, 2015;Groch et al, 2016;Wiesner et al, 2015;Hutchison and Rathore, 2015). This growing body of literature converges to support the view that "emotional arousal during encoding is beneficial to recall only if REM sleep occurs after learning" (Wiesner et al, 2015).…”

“…A subsequent study, using a multisession spatial discrimination task, showed an increase in ripples during the sleep session immediately before behavioral expression of task mastery (Ramadan et al, 2009). Interruption of ripples by ripple-triggered electrical stimulation of the hippocampus prevented learning of that same spatial discrimination task (Ego-Stengel and Wilson, 2010;Girardeau et al, 2009). Because ensemble replay happens during the ripple, it is assumed that the increase of ripples after learning will include more replay.…”