Brain wave patterns
Gamma waves - 40 hz above - these are use for higher mental activity such as for problem solving, consciousness, fear.
Beta waves - 13-39 Hz - these are for active thinking and active concentration, paranoia, cognition and arousal.
Alpha waves - 7-13 Hz - these are for pre-sleep and pre-wake drowsiness and for relaxation.
Theta waves - 4-7 Hz - these are for deep meditation, relaxation, dreams and rapid eye movement (REM) sleep.
Delta waves - 4 Hz and below are for loss of body awareness and deep dreamless sleep.