The total amount of REM sleep at night occupies about 25 per cent of the total sleep time and this proportion stays relatively constant throughout life. Hence we now know that one-quarter of our sleep is spent in dreams, and dreams are part of a healthy nightly sleep.

Now what is the importance of REM sleep and dreams? Physiologically it appears that we cannot do without REM sleep; it is an important part of the sleep cycle. Dr William Dement, the leading sleep expert, performed the following experiment with his sleep subjects. On the first night, whenever he was sure that his subjects were beginning to enter REM sleep, he woke them up and then allowed them to fall back to sleep again. This deprived his subjects of any REM sleep and hence dreams. To his surprise, the subjects appeared to enter REM sleep again and again, and more and more frequently as the morning approached. As many as 30 or more awakenings were required to prevent REM sleep from starting again. In other words, the more you try to prevent someone from dreaming, the more he has to.

The next night, Dement’s subjects were allowed to have a normal sleep without any disturbance. It was observed that they now had an excessively large proportion of REM sleep and dreams. Dement suggested that there was a need to dream. After the deprivation of REM sleep, there is a rebound as if to make up for the debt of REM sleep, and this is called REM rebound. More recent studies, however, show that suppression of REM sleep does not lead to any physiological and psychological ill-effect. The real significance of REM sleep has yet to be determined.

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