The brain contains billions of neurons that are each connected to thousands of others. Communication between them occurs through small electrical currents that travel along the neuron and throughout enormous brain circuit networks. When masses of neurons are simultaneously activated, they create synchronized electric pulses which result in a brainwave or a neural oscillation.
Brainwaves are a form of electromagnetic radiation. The difference between brain waves and other electromagnetic waves lies in their frequency. Brain waves are relatively quite slow in comparison to other forms of EM radiation, generating waves within a range of 10 to 100 Hz.
Our brainwaves tend to change depending on what we are doing or how we are feeling. When we are lethargic or feel tired, slower frequency brainwaves are more dominant. When we are active, energized, and alert, higher frequency brainwaves are more dominant.
Brainwaves are strong enough to be detected from outside of the brain using a sensing device called an electroencephalogram (EEG). An EEG is a brain monitor that tracks and records brainwave patterns and can be used to evaluate, analyze and visualize the electrical activity in the brain.
There are five main groups of brainwaves - each categorized to a specific frequency range and each associated with its own state of mind. From fastest to slowest: gamma, beta, alpha, theta, and delta.