Quantitative EEG (QEEG) is the measurement, using digital technology, of electrical patterns at the surface of the scalp which primarily reflect cortical electrical activity or "brainwaves."
Brain waves occur at various frequencies, that is, some are quick, some quite slow. The classic names for these EEG bands are delta, theta, alpha and beta. The dominant wave pattern you see above is alpha; these waves happen between 8 and 13 times per second, or 8-13 Hertz (Hz). Alpha represents a sort of "idle" state and is normally fairly large over the back third of the brain when the eyes are closed and when you are awake. Alpha disappears when we either get mentally busy (e.g., open the eyes, start doing intense mental work even eyes closed) or when we become drowsy.
Using QEEG we are able to map the brain during various assigned activities and "tests", which then give us a better idea of what is occurring within a particular individual's brain. We can use this data along with other factors such as intake interview, testing, assessments to embark upon the best course of treatment.