Why Do We Sleep, and How Much Sleep Is Necessary?
Sleep is a common and necessary altered state. Both body and mind benefit from regular patterns of sleep and wakeful- ness. However, sleep patterns vary. Some of us are short sleepers, and some of us are long sleepers. The inventor Thomas Alva Edison was famous for taking 20-minute naps throughout the daytime and nighttime hours. (Perhaps that's what it takes to invent light bulbs and phonographs!)
The Function and Meaning of Dreaming
REM sleep and dreaming are fascinating phenomena. Arguments over the purposes of dreaming and the effects of REM sleep deprivation continue. Dreaming remains a mystery to many researchers-much like consciousness itself. Your text intro- duces you to three theories that may explain the purposes of dreaming.
1. Unconscious wish-fulfillment theory-Sigmund Freud proposed that dreams reflect our deep forbidden desires. We dream what we'd really like to experience in waking life. However, the latent content of our dreams (forbidden desires) is disguised in some symbolic way behind the manifest content of dreams. A dream of a pig in clover might conceal our desire to live wild and fulfill our selfish desires.
2. Dreams-for-survival theory-Information necessary for day-to-day survival-related problem solving is processed and evaluated while we dream.
3. Activation-synthesis theory-According to Allan Hobson's model, during sleep, the brain organizes random memories and impressions into a more or less coherent "story line."
Beyond this sort of housekeeping and filing function of dreaming, Hobson doesn't entirely reject the wish- fulfillment notion.
Sleep Disturbances
Insomnia is a common problem. Most people experience this inability to sleep from time to time-usually during times of stress or inner conflict. Insomnia can be tempo- rary or chronic. President Dwight Eisenhower reportedly suffered from chronic insomnia. Apparently it wasn't unusual to find him walking in the Rose Garden in a robe and slippers in the early morning hours.
Sleep apnea is a sleep disorder related to impaired breathing. The medical causes of sleep apnea vary. The disorder may be related to an interruption of brain signals to the lungs or simply a blockage in the lungs. Sudden infant death syndrome (SIDS) appears to be related to some form of sleep apnea.
Nightmares and night terrors are two different sleep disorders. A nightmare is simply a bad dream that takes place during REM sleep. A night terror occurs during NREM sleep. The sufferer-usually a young child-will often wake in a panicked state, hallucinating. Interestingly, children can usually recall having a nightmare, but they often have no memory of a night terror.
Narcolepsy occurs as what can be thought of as micro- sleeps during waking. One goes directly from waking to REM sleep, skipping the other sleep stages. Narcoleptic events may occur during a long drive or other monotonous activities.
Somnambulism, also known as sleepwalking, occurs during stage 4 NREM sleep. Sleepwalkers often have their eyes open and appear to be awake. They sometimes talk, too. While it may appear that sleepwalkers are acting out their dreams, sleepwalking and most sleep talking don't occur during REM sleep and dreaming.
Circadian Rhythms: Life Cycles
Patterns of sleep and wakefulness typically follow 24-hour biological rhythms called circadian rhythms, which can be disrupted when we travel across time zones. This phenomenon is known as jet lag.