Figure 41. Schematic drawing showing a simplified and integrated view of the neural circuitry controlling the mammalian sleep-wake cycle. Different colors highlight the pathways for wakefulness (red and pink), NREM sleep (blue) and REM sleep (green). Continuous lines indicate primary circuitries for initiation of the sleep and waking state, dotted and hatched lines permissive circuitries for different sleep phases (NREM vs REM) and behavioral arousal, mixed colors different patterns of activity of the same center in relation to either sleep phases or wakefulness. Ach = acetylcholine; DA = dopamine; NDBB = nucleus of the diagonal band of Broca; DM = thalamic dorsomedial nucleus; DR = dorsal raphe; GABA =  aminobutyric acid; GAL = galanin; Glut = glutamic acid; His = histamine; 5HT = 5-hydroxytryptamine or serotonin; LC = locus coeruleus; LDT = laterodorsal tegmental nucleus; MCH = melanocortin-concentrating hormone; MPO = magnocellular preoptic nucleus; MSN = medial septal nucleus; NA = noradrenaline; NBM = nucleus basalis of Maynert; ORX = orexin/hypocretin; PBN = parabrachial nucleus; PPT = peduncolopontine tegmental nucleus; Reticular = thalamic reticular nucleus; vPGA = ventral periacqueductal grey; VPLO = hypothalamic ventrolateral preoptic nucleus, VPLOc = VPLO core; VPLOex = VPLO extended; TMN = hypothalamic tuberomammillary nucleus; + = stimulation; – = inhibition