ABSTRACT
Sleep seems to be essential, but the amount people need varies tremendously from extremes of less than three hours to over ten hours. Yet when volunteers have been kept awake for long periods of time, irritability, confusion, and occasionally hallucinatory and even psychotic episodes have set in. There are profound physiological and psychological changes that accompany the shift from waking to sleeping. Going to sleep seems like a simple and innocuous event, but it is accompanied by major shifts and rearrangements. In the laboratory, sleep is registered on the electroencephalogram as a change in the electrical activity of the brain in the direction of lower frequencies of brain waves and higher voltage patterns. The average adult spends about one and a half hours in dreaming sleep every night-about twenty percent of total sleep time. The effect of a stimulus upon a sleeper depends upon its intensity and when it is introduced in the sleep cycle.
