REM Sleep

1953

Eugene Aserinsky (1921–1998), William Dement (b. 1928)

Although all warm-blooded mammals dream every night, the laboratory-based study of sleep and dreams dates only from the twentieth century. By the 1930s, brain activity during sleep was measured by the new electroencephalogram (EEG) method, and rhythmic patterns were reported. However, it was not until 1953 that physiology graduate student Eugene Aserinsky identified the brain-wave pattern characterized by rapid movements of the eyes during sleep and correlated it with the state of dreaming. It was another graduate student, William Dement, who then developed the study of rapid eye movement (REM) sleep.

What scientists now know is that, during a normal night’s sleep, humans cycle through stages, each with its own characteristic brain activity. In stage one, our brains show an alpha rhythm; we can easily awake in this stage and we often experience vivid images that are not dreams. Our sleep deepens in stage two, indicated by small bursts of brain activity. During stage three, the delta rhythm of slow, large brain waves emerges; when the brain-wave pattern is only delta waves, then we are in our deepest sleep, stage four, which lasts about twenty to thirty minutes. Then lights, action! We move into REM sleep. Our heart rate and breathing quicken, and our brain-wave patterns look like they do when we are awake; our eyes move rapidly back and forth behind our eyelids (hence the name REM). Even though all this activity is going on, it is impossible to move, as our skeletal muscles are paralyzed. The first period of REM is the shortest; with each cycle—and depending on how long one sleeps, there can be as many as four cycles per night—it lengthens.

While we need each stage of sleep, research shows that REM is the most important. It is not clear why this is the case, but it is known that loss of REM sleep leads to compromised immune function. On the positive side, there is evidence that our memories are consolidated during REM.

SEE ALSO The Interpretation of Dreams (1900), Jungian Psychology (1913), Psychical Discharges (1941)

The Nightmare by Swiss-born painter Johann Heinrich Füssli, 1802.