Gregg Staton, age 12, of Richmond, Virginia, for his question:

What exactly is sleep?

Many years ago, sleep was as mysterious as the silent night. Then researchers found ways to observe certain changes that occur in the mind and body during sleep. They also observed some ghastly things that happen to a person when sleep is denied. This research still is in progress and many questions remain unanswered. However, it definitely has been proven that a person needs, really needs, a proper sleep period during each and every calendar day.

At present, nobody can say exactly what sleep is. But scientists can explain certain changes that occur throughout the body, its senses and systems, in the conscious and the unconscious minds and in patterns of the electrical brain waves. This amount of information is not bad, considering that medical researchers have been investigating the nature of sleep for only a couple of decades.

One of their most useful tools is the EEG the electroencephalograph. Its sensitive electrodes are placed on the scalp to record the electrochemical waves that continuously pulse from the busy brain. A healthy, wide awake brain pulses at the rate of about ten small waves per second, When a person falls asleep, the brainwaves grow longer and slower. During the night, they change through several patterns.

A good night's rest brings several periods of deep sleep, when thoughts become foggy and mental activity is reduced to a minimum. Between these periods there are three to five periods of lighter sleep. The brain is more active and the lidded eyes move rapidly, as though they were watching a lively TV show. A person wakened during a rapid movement period recalls a vivid dream. To get the proper rest, one should sleep long enough to let the brain repeat these patterns several times.

During sleep, the brain is busy in its own mysterious ways and meantime the body is resting also in its own mysterious ways. The heart, breathing and metabolism slow down. The blood pressure and temperature are reduced slightly. The senses grow dimmer, the conscious mind shuts down its busy switchboard and puts a hold on incoming calls. The nerves and muscles relax except for those flickering eye movements during the dream periods.

Nobody knows exactly how sleep recharges the mind and body. But experiments show what happens without it. After two sleepless days, a person loses his pep and his temper, cannot concentrate and makes a lot of silly mistakes. After ten days, a sleepless person has trouble seeing and hea and hallucinates into a whacky world where he cannot distinguish between solid reality and wild fantasy.