Sleep is important for:
concentration, memory, coordination
Stands for electroencephalography. Used to examine human brain waves during sleep.
During a normal night's sleep, the brain moves up and down through stages several times, spending less and less time in the deeper stages and more in the R.E.M. (rapid eye movement, or dreaming) stage as the night progresses.
Paralysis of all muscles (except for breathing and eye muscles) which occurs during R.E.M. sleep whilst brain waves are similar to 'awake' waves.
The most common sleep disorder which causes some people difficulty in falling asleep, and causes others to wake up in the middle of the night.