Your brain is made up of billions of brain cells called neurons, which use electricity to communicate with each other. The combination of millions of neurons sending signals at once produces an enormous amount of electrical activity in the brain, which can be detected using sensitive medical equipment (such as an EEG), measuring electricity levels over areas of the scalp.
The combination of electrical activity of the brain is commonly called a BrainWave pattern, because of its cyclic, "wave-like" nature.
Below is one of the first recordings of brain activity.
Here is a more modern EEG recording:
With the discovery of brainwaves came the discovery that electrical activity in the brain will change depending on what the person is doing. For instance, the brainwaves of a sleeping person are vastly different than the brainwaves of someone wide awake. Over the years, more sensitive equipment has brought us closer to figuring out exactly what brainwaves represent and with that, what they mean about a person's health and state of mind.
Here is a table showing the known brainwave types and their associated mental states:
The Significance of Brainwaves
You can tell a lot about a person simply by observing their brainwave patterns. For example, anxious people tend to produce an overabundance of high Beta waves while people with ADD/ADHD tend to produce an overabundance of slower Alpha/Theta brainwaves.
Researchers have found that not only are brainwaves representative of of mental state, but they can be stimulated to change a person's mental state, and this in turn can help with a variety of mental issues.
Next: Brainwave Stimulation