What are brainwaves?

You should know that your brain is made up of billions of brain cells called neurons. These neurons use electricity to communicate with each other. The combination of millions of neurons sending electrical signals at once produces an enormous amount of electrical activity in the brain, That activity can be detected using sensitive medical equipment (such as an EEG), measuring electricity levels over areas of the scalp.

Thus, the combination of electrical activity of the brain is commonly called a Brainwave pattern, because of its cyclic, 'wave-like' nature. Our mind regulates its activities by means of electric waves which are registered in the brain, emiting tiny electrochemical impulses of varied frequencies, which can be registered by an electroencephalogram. These brainwaves are known as:

1. Beta emited when we are consciously alert, or we feel agitated, tense, afraid, with frequencies ranging from 13 to 60 pulses per second in the Hertz scale.
   


2. Alpha when we are in a state of physical and mental relaxation, although aware of what is happening around us, its frequency are around 7 to 13 pulses per second.
   


3. Theta more or less 4 to 7 pulses, it is a state of somnolence with reduced consciousness.
   


4. Delta when there is unconsciousness, deep sleep or catalepsy, emitting between 0.1 and 4 cycles per second.
   

From doctorhugo.com