Electrical brain activity, as an index of central nervous system function, is studied across a range of patient groups with neurological and psychiatric disorders as well as normal volunteers. Using electrophysiological data quantified from event-related potentials and spectrum analysis of EEG recordings, computer-derived brain images are able to provide information about neurophysiological function relating to both cognition and clinical state. Topographic maps efficiently characterize spatial and temporal patterns of brain activity allowing the ability to study the dynamic interaction among brain regions and their relation to function. The project proceeds along several lines. One is to refine the topographic and quantitative methods and to employ these to establish normative baselines under various conditions. This work includes correlating topographic electrophysiological measures with structural anatomical measures derived from MRI data. This work has shown that skull and brain asymmetries are correlated with EEG asymmetries and this must be accounted for when investigating laterality. The refinement of the basic methods has led to the development of a PC based software package that is shared by a group of cooperative research laboratories. This package allows the laboratories to start with some standards of data acquisition and analysis yet have the flexibility to deal with complex research protocols. The methods employed by this package have been extended to include several transformations allowing for current source analysis and to compute coherence between specific electrode locations.
