electroencephalogram (EEG) /ilek′trō·ensef″ələgram′/ [Gk, elektron + enkephalos, brain, gramma, record] , a graphic chart on which is traced the electric potential produced by the brain cells, as detected by electrodes placed on the scalp. The resulting brain waves are called alpha, beta, delta, and theta rhythms, according to the frequencies they produce, which range from 2 to 12 cycles per second with an amplitude of up to 100 μV. Variations in brain wave activity are correlated with neurological conditions, psychological states, and level of consciousness. See also encephalography.
