Regional delta waves in human rapid-eye movement sleep.
J Neurosci. 2019 Feb 08;:
Authors: Bernardi G, Betta M, Ricciardi E, Pietrini P, Tononi G, Siclari F
Although the EEG slow wave of sleep is typically considered to be a hallmark of Non Rapid Eye Movement (NREM) sleep, recent work in mice has shown that slow waves can also occur in REM sleep. Here we investigated the presence and cortical distribution of negative delta (1-4 Hz) waves in human REM sleep by analyzing high-density EEG sleep recordings obtained in 28 healthy subjects. We identified two clusters of delta waves with distinctive properties: 1) a fronto-central cluster characterized by ∼2.5-3.0 Hz, relatively large, notched delta waves (so-called ‘sawtooth waves’) that tended to occur in bursts, were associated with increased gamma activity and rapid eye movements, and upon source modeling, displayed an occipito-temporal and a fronto-central component; and 2) a medial-occipital cluster characterized by more isolated, slower (<2 Hz) and smaller waves that were not associated with rapid eye movements, displayed a negative correlation with gamma activity and were also found in NREM sleep. Thus, delta waves are an integral part of REM sleep in humans, and the two identified subtypes (sawtooth and medial-occipital slow waves) may reflect distinct generation mechanisms and functional roles. Sawtooth waves, which are exclusive to REM sleep, share many characteristics with ponto-geniculo-occipital (PGO) waves described in animals and may represent the human equivalent or a closely related event while medial-occipital slow waves appear similar to NREM sleep slow waves.Significance StatementThe EEG slow wave is typically considered a hallmark of NREM sleep, but recent work in mice has shown that it can also occur in REM sleep. By analyzing hd-EEG recordings collected in healthy adult individuals, we show that REM-sleep is characterized by prominent delta waves also in humans. In particular, we identified two distinctive clusters of delta waves with different properties: a fronto-central cluster characterized by faster, activating ‘sawtooth waves’ that share many characteristics with PGO waves described in animals, and a medial-occipital cluster containing slow waves which are more similar to NREM-sleep slow waves. These findings indicate that REM-sleep is a spatially and temporally heterogeneous state, and may contribute to explain its known functional and phenomenological properties.
PMID: 30737310 [PubMed – as supplied by publisher]