[YOUTUBE]http://www.youtube.com/watch?v=ExYfnrlpILo[/YOUTUBE]
Alpha waves range from 8 to 12 Hz (cycles per second). Alpha waves appear to be associated with meditative and hypnotic states and sleep. One study on brainwaves and golf (356) found that alpha activity seems to be a good predictor for accurate putting; others have suggested that alpha waves tend to occur while one is absorbed in physical or mental tasks.
Beta waves range from 20 to 28 Hz and appear to be associated with active concentration and thought.
Theta waves range from 3 to 8 Hz, and seem to arise from a hippocampal circuit, possibly with the help of a circuit in the brainstem (358). Theta waves tend to decrease immediately before volitional movements, and are probably an indicator of a closed feedback loop in the limbic system. The theta rhythm may help to encode spatial and/or temporal information (359). Interestingly, the prohormone DHEA increases theta activity (357).
Delta waves, 0.3 to 3 Hz, typically occur only during non-REM sleep. NMDA antagonists (presumably including DXM) greatly increase delta waves during subsequent non-REM sleep (360).
Sigma waves, 10 to 15 Hz, seem to occur primarily during sleep.
Gamma waves, 30Hz and above, may reflect certain aspects of the cognitive process.
WARNING: Brainwave stimulation, especially in the alpha band, can induce siezures in epileptics. If you are, or suspect you might be, epileptic, don't use light and sound machines!
[YOUTUBE]http://www.youtube.com/watch?v=Mrnq8OLJYCY&feature=related[/YOUTUBE]
