It is fairly clear that the sleeping period must have some functions, and because there is
so much of it the function would seem to be important. Speculations about its nature have
been going on for literally thousands of years, and one odd finding that makes the problem
puzzling is that it looks very much as if sleeping is not simply a matter of giving the body
a rest. 'Rest', in terms of muscle relaxation an so on, can be achieved by a brief period lying,
or even sitting down. The body's tissues are self-repairing and self-restoring to a degree, and
function best when more or less continuously active. In fact a basic amount of movement occurs
during sleep which is specifically concerned with preventing muscle inactivity.
If it is not a question of resting the body, the perhaps it is the brain that needs resting? This
might be a plausible hypothesis were it not for two factors. First the electroencephalograph(which
is simply a device for recording the electrical activity of the brain by attaching electrodes to the
scalp) shows that while there is a change in the pattern of activity during sleep, there id no
evidence that the total amount of activity is any less. The second factor is more interesting and
more fundamental. Some years ago an American psychiatrist named William Dement published
experiments dealing with the recording of eye-movements, some drifting and slow, other jerky and
rapid. People woken during these periods of eye-movements generally reported that they had been
dreaming. When woken at other times they reported no dreams. If one group of people were disturbed
from their eye-movement several nights on end, and another group were disturbed from their
eye-movement sleep for several nights on end, and another group were disturbed for an equal period
of time but when they were not exhibiting eye-movements, the first group began to show some
personality disorders while the others seemed more or less unaffected. The implications of all this
were that it was not the it was not the disturbance of sleep that mattered, but the disturbance of
dreaming.