The proposed research would develop an inexpensive electro- encephalographic (EEG) amplifier system suitable for dense (128 or 256) electrode arrays. These arrays would provide the measurements necessary for new source localization algorithms constrained by MRI data that image the electrical activity of the cortex throughout the three dimensions of intracranial space. Although the anatomical resolution of these images remains to be determined, they are generated for each millisecond sample of electrical recording, and thus, provide information with a temporal resolution not possible with metabolic and hemodynamic methods of neuroimaging. This temporal resolution may be necessary to research the cognitive activity of cortical networks. The major advances in visualizing dynamic brain function promised by this new technology will have immediate applications in psychology, neurology, psychiatry, education, and human factors research. Within 5 years, this research will provide the basis for widespread clinical applications of this technology to public health problems ranging from attention deficit disorder to Alzheimer's dementia.