8 - Electrophysiological Imaging of Brain Function

Abstract

This chapter briefly reviews methodological issues in using the electroencephalogram (EEG) and stimulus-related brain electrical activity such as evoked or “event-related” potentials (ERPs) to image cognitive brain functions. It begins by briefly considering the neural basis of the EEG and its measurement at the scalp. Several innovations in EEG recording and analysis technology improving spatial resolution and integration of EEG with magnetic resonance imaging (MRI) are presented. The neurophysiology of mentation involves rapid coordination of processes in widely distributed cortical and subcortical areas. The electrical signals that accompany higher cognitive functions are subtle, are spatially complex, and change both in a tonic multisecond fashion and phasically in subsecond intervals in response to environmental demands and internal representations of environment and self. No one brain imaging technology is currently capable of providing both near-millimeter precision in localizing regions of activated tissue and subsecond temporal precision for characterizing changes in patterns of activation over time. Modern high-resolution EEG is especially well suited to monitoring rapidly changing regional patterns of neuronal activation accompanying purposive behaviors, while functional magnetic resonance imaging seems ideal for precisely determining their three-dimensional localization and distribution.