The EEG (electroencephalogram) is used to measure the electrical changes produced by the pyramidal cells on the surface of the cortex.

The quantitative electroencephalogram (QEEG) used in neurofeedback training is not looking at the quality of the brain waves (as analysed by neurologists to detect seizures for example) but rather the voltage or amplitude of certain brain waves in relation to other waves.

The brain waves recorded by the EEG are measured in frequency (how many brain waves per second) and in amplitude (the electrical potential or how many cells fire at the same time at the same speed is expressed as voltage). The frequencies or brain speed correspond to particular mindsets as summarized in the following chart.

Neurofeedback training, particularly relating to attention difficulties. is interested in the frequencies between 4 and 20 cycles per second, or hertz. The theta waves are slower brain waves in the range of 4 to 7 hertz. They are associated with a “tune-out mode”. The waves between 7 and 11 are called the alpha waves. They present a resting, daydreaming mindset.

The SMR brain waves (Sensory Motor Rhythm) refer to the waves in the 12 to 15 hertz range. They are associated with a calm but alert mental state. They allow the person to control their impulsivity while they give a feeling of quiet alertness. Barry Sterman first identified this specific frequency range, while working with cats. As he rewarded the cats to produce more SMR, their bodies were calm, but their brains were alert, ready to pounce on the mouse at the correct moment. However, when he rewarded the cats to produce less SMR, the cats were twitchy and impulsive.

The brain waves between 15 and 20 hertz are called beta. They are necessary for the focused, analytical mind set necessary to solve problems and for listening to class instructions. We see more of these waves when a person is learning a new task requiring mental effort, in comparison to doing a repetitive, already learned and mastered task