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

Sleep Disorders

Up to this point we have reviewed curious phenomena of sleep any normal person could experience. Now we move to the realm of sleep disorders, which are abnormal sleep phenomena. Many sleep disorders can be treated successfully with low doses of specific medications.

What is narcolepsy?

Narcolepsy is one of the most serious sleep disorders: a tendency to fall asleep very suddenly and unexpectedly in the middle of ordinary waking activities. The distinguishing characteristic of narcolepsy is inappropriateness of sleep occurrence. For example, it is very inappropriate to fall asleep while riding a bicycle, lecturing to a class of students, or driving a car. Normal people may experience intense sleepiness after a heavy meal or sleep deprivation, but narcoleptics fall asleep when most people would stay awake. Ernest Hilgard of Stanford used to say, "Falling asleep at a lecture is normal; falling asleep while you lecture is narcolepsy."

Why is narcolepsy dangerous?

People with narcolepsy go directly into a state resembling REM sleep, including complete muscle relaxation below the neck. Obviously this is a serious problem if a person is performing an activity such as driving a car or swimming. Therefore narcolepsy is considered a serious medical disorder. The most typical symptoms of narcolepsy are sleep attacks that can last from 30 seconds to 20 minutes but usually last 2-5 minutes. During this time the person has an irresistible urge to sleep. Some narcoleptics experience microsleeps: tiny episodes of sleep of which the person is unaware. Others experience periods of automatic behavior (with amnesia or loss of memory) during the day. Such a condition may be hard to distinguish from a dissociative fugue state and, like a fugue state, may be related to epileptic-like discharges in the brain.

What is cataplexy?

Cataplexy is "an abrupt loss of muscle tone, most often triggered by sudden, strong emotions." It occurs while a person is awake, so it is not a sleep disorder, but it probably involves the same mechanism which produces muscle paralysis in REM sleep. One research team (Siegal, Nienhius, Fahringer, Paul, Shriomani, Dement, Mignot, & Chiu, 1991) studied a dog that suffered bouts of cataplexy. The researchers found neurons in the medulla, a midbrain structure, which fired nerve impulses during two conditions: (1) during cataplexy, and (2) during muscle paralysis associated with REM sleep. They suggested, "Cataplexy results from a triggering in waking of the neurons responsible for the suppression of muscle tone in REM sleep."

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