REM sleep was discovered in 1953 by Eugene Aserinsky and Nathaniel Kleitman at the University of Chicago. While monitoring his son’s sleep, Aserinsky noticed rapid eye movements accompanied by active brain patterns - so surprising he initially assumed equipment malfunction. This accidental discovery transformed our understanding of sleep and consciousness.
REM sleep is paradoxical: the brain shows waking-level electrical activity while the body is nearly paralyzed. This atonia, generated by the brainstem, prevents acting out dreams. Disorders of this paralysis, like REM Sleep Behavior Disorder, allow sleepers to physically enact their dreams, sometimes causing injury.
REM cycles through the night in 90-minute rhythms. The first episode appears after 90 minutes and lasts 10-20 minutes. Later cycles extend to 45-60 minutes. This explains why the most elaborate dreams occur in morning hours and why those who sleep short are disproportionately REM-deprived.
The neurotransmitter profile during REM is unique: serotonin and norepinephrine nearly shut down while acetylcholine surges. The absence of norepinephrine (the stress chemical) may explain why REM processes emotional memories while reducing their distressing charge - essentially providing overnight emotional therapy.
REM sleep plays critical roles in emotional memory consolidation, creative problem-solving, and social intelligence. Subjects who slept showed dramatically higher rates of creative insight in problem-solving studies. Disruptions that suppress REM include alcohol, cannabis, most sedatives, and many antidepressants. Protecting REM sleep is essential for dream life.