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. 2014 Dec 11;8:402. doi: 10.3389/fnins.2014.00402

Figure 2.

Figure 2

(A) Hypnogram (schematic representation) of normal sleep organization: Starting at wakefulness (W), the sleeper begins the night in the lightest sleep stages 1 (N1) and 2 (N2) and progresses to the deepest stages 3 [slow wave sleep (SWS), N3] and REMS (paradoxical sleep or stage R, depicted in bold in the hypnogram). (B) Brain activity decreases during non-REMS (blue circles: Th, thalamus; BG, basal ganglia; BF, basal forebrain; PFC, prefrontal cortex; ACC, anterior cingulate cortex; and PC, precuneus) except in brainstem centers (BS). (C) Brain activity during REMS: some brain structures show increased activity during REMS (red circles: PT, pontine tegmentum; Th, thalamus; BF, basal forebrain; AMY, amygdala; HIPPO, hippocampus; ACC, anterior cingulate cortex; TA, temporal area; and OA, occipital area), while others become less active (blue circles: DLPFC, dorsolateral prefrontal cortex; PCC, posterior cingulate cortex; PC, precuneus; and IPC, inferior parietal cortex; BS, brainstem).