Delta waves are high amplitude brain waves with a frequency of oscillation between 0–4 hertz. Delta waves, like other brain waves, are recorded with an EEG and are usually associated with the deepest stages of sleep and aid in characterizing the depth of sleep.
Theta waves are frequencies in the range of 6–10 Hz, and appear when engaged in active motor behavior such as walking or other movement, and also during REM sleep. Theta waves with a lower frequency range, usually around 6–7 Hz, are sometimes observed while motionless but alert. Advanced states of consciousness or enlightenment are slow Theta waves (4-7 cycles/second) that occur in meditation. In contrast, the ordinary mind, which is an experience of the ego, is predominantly at 13+ cycles per second of beta waves.
Alpha waves are neural oscillations in the frequency range of 8–12 Hz. Alpha waves are one type of brain waves detected either by EEG) or MEG and predominantly originate from the occipital lobe during wakeful relaxation with closed eyes. Alpha waves are reduced with open eyes, drowsiness and sleep. Alpha waves do not start to appear until three years of age.
Beta waves represent the frequency range of human brain activity between 12 and 30 Hz. Beta states are the states usually associated with normal waking consciousness.
Gamma waves are patterns of neural oscillation in humans with a frequency between 25 to 100 Hz. Gamma waves are in creating the unity of conscious perception (the binding problem).
For information on specific frequencies and benefits, see the binaural beats frequency list.