An
electroencephalogram (EEG) is a (non-intrusive) recording of the electrical activity of the brain.
The recording is obtained by placing
electrodes on the scalp, usually after preparing the scalp area by light abrasion and application of a conductive gel to reduce
impedance.
Neuroscientists and biological psychiatrists use EEGs to study the function of the brain by recording EEGs during controlled behavior of human volunteers and animals in lab experiments.
See also electroencephalography. (These should be combined.)