We plan to investigate the effects of disturbed amino acid metabolism on brain performance, extending these studies from the molecular to the electrophysiological and behavioral levels of cerebral function. The investigations will be directed at uncovering metabolic changes in the lipid, protein, and amine constituents of brain that are produced by excessive concentrations of phenylalanine and other amino acids. The metabolic findings will be correlated with electrophysiological data relating to the Visual Evoked Response, which displays definitive changes depending on the level of blood phenylalanine. The findings will be used to permit an objective evaluation of the current therapeutic strategics in Phenylketonuria.