By Michelle Lease
The mind and body go through several different stages during the course of sleeping. Rapid Eye Movement (REM) sleep accounts for approximately two hours of the total sleep cycle, with the average person experiencing as many as six cycles of REM in an eight hour sleep period.
REM sleep is a time of interesting activity. The heartbeat quickens, body temperature lowers, the eyes move rapidly from side to side and other physiological events can occur, including vaginal lubrication and penile erections. In the laboratory, researchers have three primary ways of measuring body and mind activity during sleep: brain waves, eye movements and muscle tone. The activity for these areas during each stage of sleep is markedly different.
Brain activity and eye movement during sleep are recorded using electroencephalograms (EEG) measurements. Nodes are attached to the scalp, which are able to pick up the electronic impulses from the brain. The brain becomes very active during REM sleep because this is when dreaming occurs. While we can (and do) dream during the other stages of sleep, REM dreams tend to be more vivid, complex and bizarre. This REM stage has been referred to by some as the "Third Level of Existence" because the dreams occurring during this stage are as if one had traveled to another world. There are some researchers who believe the brain becomes more active during REM sleep than it is awake. REM sleep also facilitates the brains capacity for storing memories and helps the brain "rest" in preparation for its daytime (awake) activities. Freud suggested that REM may be a way of compensating for repressed experiences which occur during our waking hours; a person may dream about something that happened to them during the day that they may not have given much thought to when it was happening. This is particularly evident in children who experience nightmares as a result of watching a scary movie.
In conjunction with the brain and eye activity, the muscles become paralyzed. This is a defense mechanism which prevents us from hurting ourselves by acting out the contents of our dreams! Perhaps you have had the experience of waking up from a very sound sleep. For all intents and purposes, your mind is awake; you can hear birds singing or the radio playing, but you are also in the middle of a dream. You try to move to fully wake up, and find that you cant, because of the temporary paralysis state associated with the REM stage. This can be a frightening experience if you are unaware of what it is. Humans are not the only beings to experience the REM stage of sleep. Cats, dogs and even rats have been observed going through rapid eye movement and involuntary body movement (twitching), all part of REM sleep.
Overall, REM sleep is an important, regenerative part of the sleep process. Individuals who go through sleep deprivation have been seen to exhibit a slight reduction in memory capacity but no long-term negative effects have been found to date.
For more information, please see the related weblinks on the Stages of Sleep Homepage.
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