Fig. 1.

Important wake, NREM sleep, and REM sleep-regulating brain structures and/or nuclei, and associated neuromodulatory milieus. Wake-promoting regions, in green 1a–i; NREMS (including SWS) promoting regions in blue 2a–b; REM sleep-regulating regions in orange (3a–d). Wake (green): 1a: lateraldorsal tegmentum (LDT; Ach); 1b: pedunculopontine tegmentum (PPT; Ach); 1c: locus coeruleus (LC; NE); 1d: dorsal raphe nucleus (DRN; 5HT); 1e: tuberomammillary nucleus (TMN; Hist); 1f: hypocretin neurons of Lateral Hypothalamus (LH; Hct); 1g: cholinergic neurons of basal forebrain (BF; Ach); 1h: ventrolateral periaqueductal gray (vlPAG; DA); 1i: ventral tegmental area (VTA, DA). NREMS (blue): 2a: ventrolateral preoptic nucleus (VLPO; GABA, galanin; human homolog: intermediate nucleus (IN)); 2b: parafacial zone (PZ; GABA). REMS (orange): 3a: sublaterodorsal tegmental nucleus (SDT; Glu); 3b: ventral gigantocellular reticular nuclei (mediate REM-related muscle atonia; GABA/glycine); 3c: MCH neurons of lateral hypothalamus (LH; MCH/GABA); 3d: ventrolateral periaqueductal gray (vlPAG; GABA), *which is REM-suppressing. **LDT and PPT Ach neurons are also active during and may promote REMS, but may not play a central regulatory role