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During REM sleep, people are moving their eyes quickly without knowing it. Many other interesting things occur during the REM stage of sleep. One experiences increases in heart rate, respiration, blood pressure, muscle twitches, oxygen consumption, and gastric secretions. REM sleep is also sometimes called paradoxical sleep because the brain waves are closer to those of being awake than to those of any other type of sleep. Compare the differences of brainwave (top), eye movement (middle), and muscle tone (bottom) during Deep Sleep (immediate right) and REM Sleep (far right).
Nathaniel Kleitman discovered REM sleep in 1953. He experimented by wiring up people to various machines, including one that read the eye movement, called an electrooculogram (EOG). When he noticed eye movement, he woke up the patient. Ninety percent of patients reported having been dreaming during that time (2). If we wake up from REM sleep, we have a good chance of recalling dreams
The amount of REM sleep during a sleep period is known as the REM density (2).
Before laboratory studies, it was unknown how often and when humans dreamed. Now
it is understood that we have some shorter REM periods every 90 minutes. If we
sleep for a few hours, the REM periods usually get progressively longer. They
usually last 20-40 minutes, but can last up to an hour late in the sleeping session.
This means that if we wake up from REM sleep, we have a good chance of recalling
For a baby that has just been born, REM sleep is about 50% of their sleep. As the baby grows up, this level decreases, reaching 20-25% by adulthood.(1)
Mentally handicapped - People with a low IQ, under 70, or who are retarded, experience less REM sleep (2). This means there could possibly be a connection between how smart a person is to how much they dream, although this has not yet been proven.
There seems to be a biological and a psychological need for REM sleep, although it is not really known why. Many religions or schools of psychology see a psychological function of dreams in the symbolic dealing with or working out of an individual's conscious or unconscious problems. Here are some of the many theories for the purpose of REM sleep. (2)
(1) Morin MD, Charles M. Relief from Insomnia: Getting the Sleep of Your Dreams. New York: Doubleday Maintreet Books. 1996.
(2) "Dreams." Groliers Multimedia Encyclopedia. Apple Macintosh CDROM. Grolier, 1993. [an error occurred while processing this directive]