The brain is regulated by brain waves
Low frequecy waves, between 1 and 4 Hz, generated during deep sleep.
Wider amplitude and lower frequency waves, between 4 and 8 Hz, emited when a state of deep relaxation is reached. It is the state in which persons who are daydreaming are, as well as those meditating. These waves are used during the REM sleep phase.
Alpha is a state of relaxation and little brain activity. These waves are slower and have a wider amplitude than the Beta waves. Their frequency ranges from 8 to 14 Hz. A person who just finished a task and seat to rest is usually experimenting an Alpha state.
They are produced when the brain is involved in mental activities. They have the highest transmission speed of the four. Their frequency varies from 14 to 35 Hz. They indicate an intense mental activity. Persons using their brain for cognitive tasks emit this kind of wave.