GAMMA. Gamma waves are in the frequency range of 31 hertz (Hz) and up. It is thought that this band reflects the mechanism of consciousness; Beta and gamma waves together have been associated with attention, perception, and cognition (Rangaswamy et al., 2002).
BETA. Beta waves are in the frequency range of 12 and 30 Hz, but are often divided into beta1 and beta2 to get a more specific range, with a low voltage between 5-30 μV. This brain wave is usually associated with active thinking, active attention, focus on the outside world or solving concrete problems and is best defined in central and frontal areas of the brain. Are small and fast and can reach frequencies near 50 Hz during intense mental activity. According previous studies (Y. Zhang, Chen, Bressler, & Ding, 2009) when resisting or suppressing movement, or solving a math task, there is an increase of beta activity.
ALPHA. Alpha waves ranging from 7.5 and 12 Hz of frequency, with 30-50 μV amplitude generally; have been thought to indicate both a relaxed awareness and also inattention or disengagement. They are strongest over the occipital (back of the head) cortex and also over frontal cortex. Alpha is the most prominent wave in the whole realm of brain activity and possibly covers a greater range than has been previously thought of. It is frequent to see a peak in the beta range as high as 20 Hz, which has the characteristics of an alpha state rather than a beta, and the setting in which such a response appears also leads to the same conclusion. Alpha alone seems to indicate an empty mind rather than a relaxed one, a mindless state rather than a passive one, and can be reduced or eliminated by opening the eyes, by hearing unfamiliar sounds, or by anxiety or mental concentration. Thinking of something peaceful with eyes closed should give an increase of alpha activity; for example, several studies have found a significantly rise in alpha power after smoking marijuana (Lukas, Mendelson, & Benedikt,1995).
MU. It is an 8-12 Hz spontaneous EEG wave associated with motor activities and maximally recorded over motor cortex, basically triggers when there is an actual movement or there is an intent to move (Bernier, Dawson, Webb, & Murias, 2007). Mu wave is in the same frequency band as in the alpha wave, but this last one is recorded over occipital cortex. Most attempts to control a computer with continuous EEG measurements work by monitoring alpha or mu waves, because users can learn to change the amplitude of these two waves by making the appropriate mental effort. A person might accomplish this result, for instance, by recalling some strongly stimulating image or by raising his or her level of attention.
THETA. Theta waves lie within the range of 3.5 to 7.5 Hz, with an amplitude usually greater than 20 μV. Theta arises from emotional stress, especially frustration or disappointment. Theta has been also associated with access to unconscious material, creative inspiration and deep meditation. Are linked to inefficiency, daydreaming, and the very lowest waves of theta represent the fine line between being awake or in a sleep state. Theta arises from emotional stress, especially frustration or disappointment (L. Zhang, He, Miao, & Yang, 2005). It has also been associated with access to unconscious material, creative inspiration and deep meditation. High levels of theta are considered abnormal in adults, and are, for instance, related to attention deficit hyperactivity disorder (ADHD) (Heinrich, Gevensleven, & Strehl, 2007).
DELTA. Delta waves, ranging from 0.5 to 3.5 Hz, are the slowest waves and occurs when sleeping (Hammond, 2006). If these waves occur in the awake state, it thought to indicate physical defects in the brain. Movement can make artificial delta waves, but with an instant analysis (just observing raw EEG records), this can be verified or unconfirmed.