In 1952, Eugene Aserinsky identified and defined rapid eye movement (REM) sleep while working in the surgery of his PhD advisor. Aserinsky noticed that the sleepers' eyes fluttered beneath their closed eyelids, later using a polygraph machine to record their brainwaves during these periods. In one session, he awakened a subject who was wailing and crying out during REM and confirmed his suspicion that dreaming was occurring. In 1953, Aserinsky and his advisor published the ground-breaking study in Science.
Accumulated observation has shown that dreams are strongly associated with Rapid Eye Movement during which an electroencephalogram (EEG) shows brain activity to be most like wakefulness. Participant-nonremembered dreams during NREM sleep are normally more mundane in comparison. During a typical lifespan, a person spends a total of about six years dreaming (which is about two hours each night). Most dreams only last 5 to 20 minutes. It is unknown where in the brain dreams originate, if there is a single origin for dreams or if multiple portions of the brain are involved, or what the purpose of dreaming is for the body or mind.