Facts About Sleep
each day. An attack is more likely to occur when the person is involved in passive and boring work, but narcolepsy can be triggered by strong emotions as well. Narcolepsy is typically accompanied by one or more of the following symptoms: cataplexy (sudden loss of muscular tonus, causing the person to fall down while fully conscious), sleep paralysis (an inability to move that develops in the transition between arousal and sleep), and hypnagogic hallucinations (vivid visual and auditory sensations occurring at the onset of sleep). People who suffer from narcolepsy go into the REM sleep stage directly from an awake state. However, they have a lower proportion of REM sleep than do other people. Narcolepsy tends to run in families. It usually begins at puberty and continues for the remainder of the person’s life. The Function of Sleep and Dreams It is likely that sleep is functionally important because it has persisted throughout the evolution of mammals and birds. In the laboratory, rats that have been deprived of sleep for two to three weeks will die. There are several theories regarding the function of sleep. • Conservation of metabolic energy: The idea that sleep con-
serves energy is supported by the fact that humans increase their food intake during sleep deprivation. The idea that sleep enforces body rest is supported by the fact that small mammals tend to sleep the most. Since we feel refreshed after sleep, this theory is appealing. • Thermoregulation: There are strong indications that sleep has thermoregulatory functions. Body and brain temperatures are usually reduced during sleep. • Neural maturation and mental health: The idea that REM sleep aids neural maturation is strongly supported by the association of REM sleep and immaturity at birth across
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