During wakefulness,
hypocretin(Hcrt)
activity excites
noradrenergic(green),
histaminergic
(deep blue) and
serotonergic(yellow)
neurons, which give rise to enhanced cortical
activity and arousal. Slow-wave sleep (SWS) is
characterized by synchronous intrinsic cortical
activity, and most subcortical afferents show
reduced activity. During rapid eye movement
(REM) sleep, low hypocretin activity results in
the disinhibition of REM-on
cholinergic neurons
(orange). DRN, dorsal raphe nucleus;
LC, locus coeruleus; PPT, pedunculopontine
tegmental nucleus; PRF, pontine reticular
formation; TMN, tuberomammillary nucleus.