The electroencephalogram or EEG has long been used to get information about brainwave activity in people. Electrodes are placed on the scalp and the ongoing electrical activity can be monitored and evaluated by clinicians. The EEG is useful for identifying many neurological problems including seizure activity or sleep disturbances but it is limited in that it gives information about ongoing brainwaves in real time.

The QEEG is in some ways similar to the EEG in that it also gives information about brainwave activity in people. Electrodes are placed on the scalp and brainwave activity is recorded while the person is engaged in several types of task. Recordings are made with the eyes open and with the eyes closed to help distinguish the kind of brain activity that occurs during these two conditions. Brainwaves are also recorded during several types of cognitive tasks such as reading or doing math problems to try to identify the brainwaves that occur under task.

Analysis of the QEEG is made by digitizing the brain wave activity. QEEG recordings are compared to large databases which are matched to the individual by age and gender. These databases normalize brain wave activity and any statistical deviations from the database will show up in the QEEG.

QEEG has tremendous value in identifying brain regions in which there is over or under activity. Many conditions such as ADD or depression will be evident from QEEG data. Coherence, which is a measure of how well different areas of the brain communicate with one another, is analyzed in the QEEG.