Sleep selectively stabilizes contextual aspects of negative memories

Abstract

Sleep and emotion are both powerful modulators of the long-term stability of episodic memories, but precisely how these factors interact remains unresolved. We assessed changes in item recognition, contextual memory, and affective tone for negative and neutral memories across a 12 h interval containing sleep or wakefulness in 71 human volunteers. Our data indicate a sleep-dependent stabilization of negative contextual memories, in a way not seen for neutral memories, item recognition, or across wakefulness. Furthermore, retention of contextual memories was positively associated with the proportion of time spent in non-rapid eye movement sleep in a valence-independent manner. Finally, while affective responses to previously seen negative stimuli and to both old and new neutral stimuli decreased across an interval of sleep, effects for memorized items did not differ reliably between sleep and wake. These results add to our understanding of the complex interrelations among sleep, memory, and emotion.

Sleep differentially impacts involuntary intrusions and voluntary recognitions of lab‐analogue traumatic memories

“…Furthermore, while memories are consolidated during sleep, research suggests that sleep attenuates the affective tones of emotional memories (Cox et al, 2018;Cunningham et al, 2014). Supporting this theoretical account, research has found that post-trauma sleep (versus staying awake) led to fewer and less distressful involuntary intrusions (Kleim et al, 2016;Porcheret et al, 2019;Woud et al, 2018).…”

“…Indeed, mounting evidences suggest sleep preferentially consolidates emotional memories and makes them long‐lasting (Cox et al., 2018; Hu et al., 2006; Wagner et al., 2001). Besides memories, a few studies suggested sleep may also preserve affective tones of emotional memories, indicated by subjective and physiological responses (Ashton et al., 2019; Baran et al., 2012; Menz et al., 2013; but also see Cox et al., 2018; Cunningham et al., 2014; Van Der Helm et al., 2011 for discrepant findings). Accordingly, one tenable hypothesis is that sleep deprivation in the early aftermath of trauma may alleviate PTSD symptoms, including involuntary intrusions and emotional hyperarousal.…”

“…memories, indicated by subjective and physiological responses (Ashton et al, 2019;Baran et al, 2012;Menz et al, 2013; but also see Cox et al, 2018;Cunningham et al, 2014;Van Der Helm et al, 2011 for discrepant findings). Accordingly, one tenable hypothesis is that sleep deprivation in the early aftermath of trauma may alleviate PTSD symptoms, including involuntary intrusions and emotional hyperarousal.…”

“…Disrupted sleep could be an adaptive consequence of traumatic experiences that prevents traumatic memories from being consolidated. Indeed, mounting evidences suggest sleep preferentially consolidates emotional memories and makes them long-lasting (Cox et al, 2018;Hu et al, 2006;Wagner et al, 2001). Besides memories, a few studies suggested sleep may also preserve affective tones of emotional…”

Why We Sleep: A Hypothesis for an Ultimate or Evolutionary Origin for Sleep and Other Physiological Rhythms

“…Restorative, or recuperative theories hypothesize that sleep serves one or more of the following functions: to rest and repair [13,14]; to consolidate what we have learned while we were awake [7,15,16,17,18]; to dream [19]; to enhance the immune response [15,19,20,21]; to avoid the serious detrimental effects of deprivation [1,4,9,22]; to detoxify [23].…”