Increased heartbeat-evoked potential during REM sleep in nightmare disorder

https://doi.org/10.1016/j.nicl.2019.101701Get rights and content
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Highlights

  • We used heartbeat-evoked EEG potential (HEP) as an index of emotional arousal.

  • Nightmare patients had higher HEP amplitude during REM sleep compared to controls.

  • This increase specifically concerned a cluster of frontal electrodes.

  • Higher HEP indicates elevated emotional arousal during REM sleep in this disorder.

Abstract

Nightmares are characterized by the experience of strong negative emotions occurring mainly during REM sleep. Some people suffer from nightmare disorder, which is defined by the repeated occurrence of nightmares and by significant distress in wakefulness. Yet, whether frequent nightmares relate to a general increase in emotional reactivity or arousal during sleep remains unclear. To address this question, we recorded heartbeat-evoked potentials (HEPs) during wakefulness, NREM and REM sleep in patients with nightmare disorder and healthy participants. The HEP represents a cortical (EEG) response to the heartbeat and indexes brain-body interactions, such as interoceptive processing and intrinsic levels of arousal. HEP amplitude is typically increased during states of high emotional arousal and motivation, and is decreased in depression. Here we compared the amplitude of HEPs between nightmare patients and healthy controls separately during AWAKE, NREM, REM periods, and found higher HEP amplitude in nightmare patients compared to healthy controls over a cluster of frontal regions only during REM sleep. This effect was not paralleled by any group difference in cardiac control measures (e.g. heart rate variability, interbeat interval). These findings corroborate the notion that nightmares are essentially a REM pathology and suggest that increased emotional arousal during REM sleep, as measured by HEP, is a physiological condition responsible for frequent nightmares. This result also supports that HEP may be used as a biomarker of increased emotional and sensory processing during REM sleep in these patients.

Keywords

Nightmares
REM sleep
Heartbeat-evoked potential
EEG
Emotional arousal

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These authors contributed equally to this manuscript.