Abstract

SummaryObjectiveRapid eye movement (REM) sleep has a suppressing effect on epileptic activity. This effect might be directly related to neuronal desynchronization mediated by cholinergic neurotransmission. We investigated whether interictal epileptiform discharges (IEDs) and high frequency oscillations—a biomarker of the epileptogenic zone—are evenly distributed across phasic and tonic REM sleep. We hypothesized that IEDs are more suppressed during phasic REM sleep because of additional cholinergic drive.MethodsTwelve patients underwent polysomnography during long‐term combined scalp‐intracerebral electroencephalography (EEG) recording. After sleep staging in the scalp EEG, we identified segments of REM sleep with rapid eye movements (phasic REM) and segments of REM sleep without rapid eye movements (tonic REM). In the intracerebral EEG, we computed the power in frequencies <30 Hz and from 30 to 500 Hz, and marked IEDs, ripples (>80 Hz) and fast ripples (>250 Hz). We grouped the intracerebral channels into channels in the seizure‐onset zone (SOZ), the exclusively irritative zone (EIZ), and the normal zone (NoZ).ResultsPower in frequencies <30 Hz was lower during phasic than tonic REM sleep (p < 0.001), most likely reflecting increased desynchronization. IEDs, ripples and fast ripples, were less frequent during phasic than tonic REM sleep (phasic REM sleep: 39% of spikes, 35% of ripples, 18% of fast ripples, tonic REM sleep: 61% of spikes, 65% of ripples, 82% of fast ripples; p < 0.001). In contrast to ripples in the epileptogenic zone, physiologic ripples were more abundant during phasic REM sleep (phasic REM sleep: 73% in NoZ, 30% in EIZ, 28% in SOZ, tonic REM sleep: 27% in NoZ, 70% in EIZ, 72% in SOZ; p < 0.001).SignificancePhasic REM sleep has an enhanced suppressive effect on IEDs, corroborating the role of EEG desynchronization in the suppression of interictal epileptic activity. In contrast, physiologic ripples were increased during phasic REM sleep, possibly reflecting REM‐related memory consolidation and dreaming.

Highlights

  • Rapid eye movement (REM) sleep has a suppressing effect on epileptic activity

  • When comparing phasic and tonic REM sleep, we found that the mean ripple rate in normal zone (NoZ) was significantly higher in phasic REM sleep compared to tonic REM sleep (0.49/min during phasic REM sleep vs. 0.18/min during tonic REM sleep, p < 0.001), whereas the opposite was true for ripples in channels with interictal epileptiform discharges (IEDs) both outside and inside the seizure onset zone (EIZ 0.57/min during phasic REM sleep vs. 1.28/min during tonic REM sleep, p < 0.001; seizure-onset zone (SOZ), 1.05/ min during phasic REM sleep vs. 2.64/min during tonic REM sleep, p < 0.001)

  • We demonstrated that [1] phasic REM sleep has an enhanced suppressive effect on IEDs and High-frequency oscillations (HFOs) compared with tonic REM sleep, and that [2] ripples in regions with epileptic activity show a different behavior regarding the coupling to phasic versus tonic REM sleep compared to ripples in presumably normal brain regions

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Summary

Introduction

Rapid eye movement (REM) sleep has a suppressing effect on epileptic activity. This effect might be directly related to neuronal desynchronization mediated by cholinergic neurotransmission. We investigated whether interictal epileptiform discharges (IEDs) and high frequency oscillations—a biomarker of the epileptogenic zone —are evenly distributed across phasic and tonic REM sleep. Results: Power in frequencies

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