ABSTRACT
Sleep is a physiological and biological state of almost all inhabitants on the earth [1]. Sleep has been described by early scientists as a passive condition where the brain is isolated from the rest of the body. Alcmaeon claimed that sleep is caused by the blood receding from the blood vessels in the skin to the interior parts of the body. Philosopher and scientist Aristotle suggested that while food is being digested, vapors rise from the stomach and penetrate into the head. As the brain cools, the vapors condense, flow downward and then cool the heart, which causes sleep. Some others still claim that toxins that poison the brain cause sleep [2]. With the discovery of brain waves and later the discovery of the EEG system, the way sleep was studied changed.
