Facts and artifacts in brain electrical activity mapping.

As computerized EEG (CEEG) analysis and display methods become increasingly powerful the user is lured toward increasingly abstract representations of data in which artifacts can easily go unrecognized. The presence of even small amounts of artifact can lead to distortion of CEEG results due to the sensitivity of the analysis methods employed. Several common artifacts are discussed, their distortion of CEEG data illustrated, and remedial measures suggested. Some of these artifacts (EOG, EMG, photomyoclonic, tremor, ECG, 60 Hz, volume conducted cortical activity) are familiar to traditional EEG (aliasing, extrapolation) are unique to CEEG and may be inadvertently introduced by workers not specifically trained in CEEG methods.