REM Sleep Depotentiates Amygdala Activity to Previous Emotional Experiences

Abstract

Summary Clinical evidence suggests a potentially causal interaction between sleep and affective brain function; nearly all mood disorders display co-occurring sleep abnormalities, commonly involving rapid-eye movement (REM) sleep [1–4]. Building on this clinical evidence, recent neurobiological frameworks have hypothesized a benefit of REM sleep in palliatively decreasing next-day brain reactivity to recent waking emotional experiences [5, 6]. Specifically, the marked suppression of central adrenergic neurotransmitters during REM (commonly implicated in arousal and stress), coupled with activation in amygdala-hippocampal networks that encode salient events, is proposed to (re)process and de-potentiate previous affective experiences, decreasing their emotional intensity [3]. In contrast, the failure of such adrenergic reduction during REM sleep has been described in anxiety disorders, indexed by persistent high-frequency electroencephalographic (EEG) activity (>30Hz) [7–10]; a candidate factor contributing to hyper-arousal and exaggerated amygdala reactivity [3, 11–13]. Despite these neurobiological frameworks, and their predictions, the proposed benefit of REM sleep physiology in de-potentiating neural and behavioral responsivity to prior emotional events remains unknown. Here, we demonstrate that REM sleep physiology is associated with an overnight dissipation of amygdala activity in response to previous emotional experiences, altering functional-connectivity and reducing next-day subjective emotionality.

Slow dissolving of emotional distress contributes to hyperarousal

“…Least-squares regression lines (thick lines) and 95% confidence interval bounds (thin lines) of the association between insomnia severity and the frequency of occurrence of short-lasting (gray) and long-lasting (black) distress after a shameful experience are shown. emotional experiences, both subjectively and objectively, at the level of limbic brain reactivity (10,(12)(13)(14). We hypothesized that this beneficial effect may be attenuated in conditions characterized by restless REM sleep (5,17).…”

“…Naps containing REM sleep were shown to resolve emotional reactivity, whereas naps without REM sleep did not (12). Furthermore, high-frequency electroencephalographic activity during REM sleep, an index of fragmented REM sleep, hinders resolution of emotional distress (10).…”

“…Although sleep contributes to the more robust consolidation of emotional memories, relative to neutral memories (7,8), their later recall is not associated with anywhere near the same magnitude of subjective emotional distress, autonomic arousal, and amygdala activation (7,(9)(10)(11). REM sleep plays an important role in this process (10,(12)(13)(14), although not excluding a role for nonrapid-eye-movement (NREM) sleep (15).…”

“…REM sleep plays an important role in this process (10,(12)(13)(14), although not excluding a role for nonrapid-eye-movement (NREM) sleep (15). Naps containing REM sleep were shown to resolve emotional reactivity, whereas naps without REM sleep did not (12).…”

Sleep sharpens sensory stimulus coding in human visual cortex after fear conditioning

“…Because the goal of our study was to study the impact of sleep on the perceptual discrimination of conditioned visual stimuli, we purposefully chose experimental conditions minimizing any additional stress that would interfere with the consolidation of a newly acquired emotional association. For this reason, we also deliberately avoided sleep deprivation in the Wake group, which is known to elicit high levels of stress (van der Helm et al, 2011).…”