Neurobiology of Dreaming

There is not a universally agreed upon biological definition of dreaming. 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.[4] In 1953, Aserinsky and his advisor published the ground-breaking study in Science.[5]

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.[6] During a typical lifespan, a person spends a total of about six years dreaming[7] (which is about two hours each night).[8] Most dreams only last 5 to 20 minutes.[7] 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.

During REM sleep, the release of the neurotransmitters norepinephrine, serotonin and histamine is completely suppressed.[9][10][11] As a result, motor neurons are not stimulated, a condition known as REM atonia. This prevents dreams from resulting in dangerous movements of the body.

According to a report in the journal Neuron, rat brains show evidence of complex activity during sleep, including the activation in memory of long sequences of activity.[12][13] Studies show that various species of mammals and birds experience REM during sleep,[14] and follow the same series of sleeping states as humans.[12]

Despite their power to bewilder, arouse, frighten or amuse, dreams can often be ignored in mainstream models of cognitive psychology.[15] As...