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. 2022 Aug 21;10(2):198–234. doi: 10.1080/23328940.2022.2109932

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© 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

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Figure 1. — Sleep stages in humans. Electroencephalogram (EEG) patterns during sleep in humans characterize sleep stage which differ in the frequency and amplitude of EEG waves. Stage 1 is denoted by low-amplitude waveforms. Stage 2 shows higher frequency waves or sleep spindles as well as K complexes (not shown). Stages 3 and 4 or slow-wave sleep (SWS) show high-amplitude waves. These three stages also referred to as N1, N2, and N3 sleep comprise non-rapid eye movement (NREM) sleep. Rapid eye movement (REM) sleep is characterized fast, low amplitude, desynchronized brainwaves that resemble the EEG pattern of wakefulness. Figure reprinted from Bryant et al. [28] with permission.