EEG and ERP Imaging of Brain Function

Abstract

The purpose of functional brain mapping is to localize patterns of neuronal activity associated with sensory, motor, and cognitive functions, or with disease processes. To be complete, an imaging modality needs near millimeter precision in localizing regions of activated tissue and sub-second temporal precision for characterizing changes in patterns of activation over time. Increasingly fine anatomical resolution is available with functional magnetic resonance imaging (fMRI). However, fMRI is an indirect measure of neuronal electrical activity whose temporal resolution is too gross to resolve the rapidly shifting patterns of activity that are characteristic of actual neurophysiological processes. In contrast, electroencephalography (EEG) and event-related potential (ERP) methods have a temporal resolution typically in the one to five millisecond range, depending on the AID rate. For simplicity the term EEG is used here in a general sense to refer both to recordings of brain electrical activity and, except where noted, to recordings of brain magnetic activity called magnetoencephalograms or MEGs. The nature of MEG recording technology and the relative strengths and weaknesses of EEG versus MEG approaches have been reviewed elsewhere (Cohen & Cuffin, 1991; Leahy et al., 1998; Williamson & Kaufman, 1987). From a broad perspective that considers all neuroimaging modalities, the differences between EEG and MEG are slight relative to their similarities.