Brain waves are defined as rhythmic fluctuation of electric potential between parts of the brain as seen on an electroencephalogram (EEG).
To measure brain waves electrodes are placed onto the scalp using the EEG.
There are four types of brainwaves:
Beta brain waves:
Beta brain waves occur between 14 - 30 Hz but during intense mental activity can reach 50 Hz i.e., Beta waves characterize the conscious waking state at 14 cycles per second and up.
Beta waves occur in individuals who are attentive and alert to external stimuli or exert specific mental effort. Beta waves also occur during deep sleep, REM (Rapid Eye Movement) sleep when the eyes switch back and forth.
Notice that the amplitude of beta rhythms tends to be less than for alpha rhythms. This does not mean that there is less electrical activity rather that the "positive" and "negative" activities are starting to counterbalance so that the sum of the electrical activity is less.
Thus, instead of getting the wave-like synchronized pattern of alpha waves, desynchronization or alpha block occurs. So, the beta wave represents excitement of the cortex to a higher state of alertness or tension
Alpha brain waves:
Alpha brain waves occur between 8 - 13 Hz i.e.,the alpha state operates at a lower cycle, 7-14 cycles per second level. In general, the alpha rhythm is the prominent EEG wave pattern of an adult who is awake but relaxed with eyes closed.
When we relax and clear our minds of wandering thoughts or simply choose to ignore them, our brains generate alpha waves. In the alpha state, one is open to suggestion as the conscious logical mind is subdued.
Each region of the brain has a characteristic alpha rhythm but alpha waves of the greatest amplitude are recorded from the occipital and parietal regions of the cerebral cortex. Psychic experiences can happen in the alpha state. Both daydreaming and sleep dreaming occur while in the alpha state.
Theta brain waves:
Theta brainwaves occur between 4 - 7 Hz i.e.,the theta state is 4 - 7 cycles per second. When you enter this type of mental activity such as daydreaming, fantasy, imagination, ideas, inspirational thinking, your brain generates theta brain waves.
Theta wave generation can be stimulated by a number of activities and sources. While it is possible to have psychic experiences in the alpha state, the most thoughtful experiences occur at the theta level. If you drive for a long while on a straight road, you can go into Theta state.
The theta level opens the door to fall down even deeper into the psychic/astral world.. At this level, one is able to experience astral travel and psychic communication, achieve enlightenment, and enter into other dimensions.
Delta brain waves:
Delta brainwaves occur below 3.5 Hz i.e., brain wave activity in the delta state ranges from 0 - 4 cycles per second. This is total unconsciousness, deep, dreamless sleep. When we are asleep and not dreaming, the brain generates delta waves.
Delta brain waves may increase during difficult mental activities requiring concentration. In general, the occurrence and amplitudes of delta and theta rhythms are highly variable within and between individuals.