Evidence that monoamines influence human evoked potentials.

We have measured latency and flash/pattern differentials of the visual evoked potential (VEP) from phenylketonuric humans, while systematically manipulating rates of amine synthesis in the central nervous system using two techniques. We have observed that stimulation of monoaminergic activity in the visual processing system, either by lowering inhibitory levels of phenylalanine through dietary restriction or by a properly balanced administration of indole and catecholamine precursors, shortened VEP latencies and permitted the development of a discriminative brain response to patterned stimuli. The close temporal relationship between these electrophysiological changes and the neurochemical manipulations following treatment initiation of discontinuation argue that monoamines play a significant role in the mediation of human sensory evoked potentials.