The sleep cycleThe sequence of sleep stages -- from light sleep to deep sleep to light sleep to REM sleep -- is repeated several times each night. Most individuals who sleep 6 to 9 hours per night have 3 to 5 periods of REM sleep. That means almost everyone has several dreams per night. Why don't you recall all those dreams? It turns out that the dream is a fleeting experience, and is usually forgotten by morning unless you are awakened during the dream or within about 3 minutes after the REM period ends.As you go through a typical night, initially you spend more time in deep, slow-wave sleep, but shift to more REM sleep as morning approaches. This pattern is illustrated on the next page. |