Brain waves during the sleep differ from ones during the wake. When we are awake, brain generates low amplitude waves (alpha-waves) and when we sleep it generates high amplitude waves (delta ant theta waves). That is related with the fact that during wake electric impulses of nerve cells are not synchronized. That's why we can see such high-frequency oscillations. During the sleep most of cells are synchronized and we've got slow high-amplitude waves.
In XIX-th century physiologist Mary Manasseine during her experiments on animals proved that lack of sleep causes death. Need for sleep arises when the brain is overwhelmed with information. After we took some food our stomach digests that. Something similar takes place during a sleep. A brain "takes food of impressions" during the day. It needs time to process all that data and to extract all "vitamins", "minerals" and other useful "substances" for mind. Lack of sleep comparable with gluttony. Both of them causes death. Mach faster than death from hunger. The same happens with sleep. A Man needs to "disconnect" from reality, to "digest" gathered information. Otherwise we'll have the following process.
1st of March - International day of Sleep, declared by Wolrd Fund of Psychic Health
