This is the 2007 version. Click here for the 2017 chapter 03 table of contents.

Summary: Sleep

The "golden age of sleep research" started in the 1950s with the discovery of Rapid Eye Movement (REM) sleep in both humans and animals. Researchers at the University of Chicago sleep laboratory discovered that people wakened during REM sleep almost always reported dreams. Now scientists realize that dreaming involves a circuit in the forebrain, and the onset of REM sleep often activates this circuit, but REM sleep is not equivalent to dreaming. That is why one can have vivid, story-like dreams immediately upon falling asleep, while the first REM period does not occur for nearly an hour after falling asleep.

Cats with a part of the midbrain removed appear to act out their dreams. They show fighting or attack motions during REM sleep. People awakened from REM sleep usually report a dream with a bizarre, story-like character in which the dreamer is an active and believing participant. People awakened from non-REM or slow wave sleep also report mental activity, but it is more like fragments of ordinary thought. Students asked to judge which dreams came from REM or non-REM sleep have no trouble telling them apart.

College students in one large-scale study averaged about 7.2 hours of sleep per night, with large variations. Studies of short-term sleep deprivation showed it does not have any harmful consequences. However, a sleep-deprived person is likely to experience lapses of attention or involuntary microsleep periods if involved in a boring activity like driving or listening to a lecture.

Many unusual events occur during sleep. Some, like sleepwalking and sleeptalking, are common during childhood or when a person is under stress. Most people have experienced the hypnagogic state (the state of falling asleep, sometimes accompanied by complex images) and the hypnopompic state (the state of waking up out of a deep sleep, often accompanied by feelings of confusion or disorientation).

Sleep disorders are unusual sleep-related events that are harmful or abnormal or disruptive to individuals. Narcolepsy occurs when a person falls suddenly and without warning into REM sleep. Sleep apneas are periods of breathlessness during sleep. Night terrors are severe nightmares that occur when a child is deeply asleep. Although the syndrome is frightening to parents, children usually outgrow it without harm.

Dreaming is a universal human experience, although some people go through a mental shift while awakening which makes it difficult for them to recall dreams. A list of common dream themes in Solomon Islanders and college students shows many similar topics such as being frozen with fright and eating delicious food. Lucid dreams, in which a person knows he or she is dreaming while still asleep, are rare events for most people, although some researchers believe they can be made more frequent by following simple procedures.

Meaningful dreams—those that have obvious relevance to a person's life—sometimes take the form of warnings or inspirations. Most psychologists do not believe dreams can be interpreted using dream books which give fixed interpretations of symbols.


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