TOPICS: Sleep cycle, circadian rhythm, suprachiasmatic nucleus (SCN) of hypothalamus, norepinephrine (NE), pineal gland, melatonin, sleep stages, non-REM sleep, stage N1, stage N2, stage N3, REM sleep, beta waves, alpha waves, hypnagogic hallucinations, theta waves, bruxism, sleep spindles, K complexes, sleepwalking, night terrors, enuresis, delta waves, electroencephalogram (EEG), memory, paramedian pontine reticular formation, alcohol, benzodiazepines, barbiturates, sleep changes in elderly, sleep changes in depression, sleep terror disorder, REM latency, desmopressin, narcolepsy, hypocretin (orexin), cataplexy, hypnagogic hallucinations, hypnopompic hallucinations, stimulants, modafinil, sodium oxybate