Midsagittal view of the brain showing a close up of the hypothalamus. The hypothalamus controls the circadian rhythms that guide the body’s natural sleeping and waking cycles. Highlighted are the suprachiasmatic nucleus (in yellow) which sets basic circadian rhythms, the pre optic are (in lavender) which controls slow wake sleep, and the posterior hypothalamic nucleus (in blue) which promotes wakefulness. Overlaying ECG patterns show a waking state, deep sleep and REM sleep.