The proposed research would develop and commercialize an inexpensive electroencephalographic (EEG) amplifier system suitable for dense (128 or 256) sensor arrays. The innovations of this design include an elementary low-noise analog circuit and isolation after multiplexing and digitization to minimize the parts count and maximize the digital signal processing now readily available on the host computer. This technology would provide the measurements necessary for new electrophysiological neuroimaging methods, including source localization algorithms constrained by MRI data on head anatomy. 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 advances in visualizing dynamic brain function promised by this new technology will have applications in psychology, neurology, psychiatry, education, and human factors research.