Home > Encyclopedia of Psychology > Electroencephalograph (EEG)

A device used to record the electrical activity of the brain.

Electroencephalography is used for a variety of research and diagnostic purposes. It is usually conducted using electrodes, metal discs attached to the scalp or to wires connected to the skull or even to the brain itself. The signals obtained through the electrodes must then be amplified in order to be interpreted. EEG patterns typically take the form of waves, which may be measured according to both their frequency and size (also referred to as amplitude). The electrical activity of animals' brains had been recorded as early as 1875, but it was not until 1929 that the first human EEG was reported by Austrian psychiatrist Anton Berger. Since then, it has been used to study the effects of drugs on the brain, as well as the localization of certain behavioral functions in...