This volume is the second in "The Downstate Series of Research in Psychiatry." It is aseries devoted to the presentation of sig­ nificant research with relevance for both clinicians and researchers in the multiple subfields of psychiatry. This book focuses on the interactions between psychic phenomena and physical processes as studied by evoked brain potentials. It presents material concerned with physiological and psychological unifying processes, as weIl as research concerning technology and methods of obtaining meaningful measurements. As such it is representative of biological psychiatry at its best. Thus, it represents another step in new directions in psychiatric research but not an unanticipated direction. Scientific investigation into the human psyche took an unex­ pected turn when Sigmund Freud in the last part of the 19th Century turned his attention from neurological concerns to those of psychol­ ogy. His first attempts at explanations as noted in the "project," included a heavy emphasis on the biological substrate of behavior.