The general purpose of this research is to establish electrophysiologic correlates of psychiatric illness. Such correlates may then serve to focus animal research on underlying mechanisms. EEG and evoked potential (EP) data are obtained in different clinical groups and analyzed in various ways with computer assistance. Patients are followed through treatment with serial determinations to assess the effects of drugs. The main EP experimental procedure currently employed involves pseudorandomized presentation of electrical pulses to right and left wrists, full field visual checkerboard flash, binaural click, with monopolar recording from 15 leads; on-line averaging is in two modes, to assess short- and longer term variability. EEGs are subjected to coherence and amplitude and frequency time series analyses. EPs are analyzed for amplitude, latency, and waveshape stability. Reduced data are treated statistically with multivariate procedures. Another paradigm involves selective attention; the subject counts the stimuli to one of four randomly stimulated fingers. Some recent results of interest are: (a) The extent of deviation from normal in EP characteristics in psychiatric patients, mainly reduced later component amplitudes, was correlated with IQ, lower IQ patients being more deviant. (b)) Both antipsychotic adn tricyclic antidepressant drugs tended to normalize somatosensory and auditory, but not visual, EPs. (c) An EEG measure of cortical coupling revealed striking changes in patterns of functional linkage between brain areas during visual activity. (d) Somatosensory EPs showed three kinds of changes associated with selective attention. To further investigate the deviant distribution of brain activity suggested by the EP topographic findings, an 8-channel rheoencephalographic recorder was developed to provide measures reflecting regional cerebral blood flow; its validity is being tested with simple lateralized motor maneuvers.