Page 37, Section 2.3

 Consciousness exists in forms other than your normal waking state.  Altered states of consciousness take you into a world where sensations and perceptions are no longer restricted by everyday reality.  During dreams, example, you might fly with eagles, meet a long-dead friend or struggle to escape the grasp of a monster.

 Sleep and dreams provide by far your most common altered state of consciousness experiences.  Although much mystery still surrounds the role of sleep and dreams in your life, both are now being studied in great depth.

 The EEG machine translates your brain waves into visible patterns that can be see on a screen or printed on a piece of paper.

 When you fall asleep, your body shuts down some of its busy activities.  You become less sensitive to outside (stimuli) and your brain waves (measured in cycles per second, or CPS) slow down from their usual cps.  Studies of the patterns of these brain waves on an EEG machine show that sleep is made up of four different levels, or stages.

 About 75% percent of your sleep time is spent in stages II, III, and IV.  During stage IV sleep, brain waves are reduced to about 3 CPS  Sleepwalking and talking, if they occur at all, usually happen during this deep sleep.

 Stage I sleep, unlike the other three stages, is marked by brain-wave activity remarkable similar to normal consciousness.  From time to time during Stage I sleep, your eyes dart back and forth beneath your closed eyelids as if they are following some interesting event.  These rapid eye movements give this type of sleep the name REM sleep.

 If someone wakes you during a period of REM sleep, you’ll probably remember that you’ve been dreaming, for dreams occur only during REM sleep.  Dream periods occur about every 90 minutes during the night but increase length toward morning.

 Dreams themselves are “stories” that your brain makes up during sleep. Like any good story, dreams include visual images, characters, and emotions.  But like a badly edited film, dreams often ignore the rules of reality.  They jump back and forth in time, invent new identities for old friends, and frequently defy common sense.

 Your body, however, moves very little during even the most active dreams.  Hormone levels rise as if you were actually taking part in an emotional experience, but the brain “turns off” your muscles so you won’t thrash around during those spectacular chase scenes.