Branched chain amino acids decrease top-down event-related potentials in healthy subjects

Introduction: Cerebral dopamine is thought to be crucially involved in cognitive processing. Branched chain amino acids (BCAAs) acutely lower cerebral dopamine precursor availability and induce short-term dopamine depletion. We examined the effects of acute dopamine depletion on cortical processing via event-related potentials (ERPs). Methods: Serum prolactin levels and attentive ERP components N2 (MMN/N2b) and P3b were investigated using high-density electroencephalography in 22 healthy male subjects after receiving BCAAs or placebo in a randomized, double-blind, placebo-controlled crossover design. Results: BCAAs increased serum prolactin levels and reduced ERP component N2 (MMN/N2b). Subcomponent analysis revealed an attenuation of early attentive N2b over fronto-central scalp sites, while late attentive prefrontal P3b showed trend-level reductions. MMN was not affected. Conclusions: Dopaminergic neurotransmission seems to be involved in early top-down processing as indexed by selective reduction of prefrontal N2b during dopamine depletion. In healthy male subjects, early cortical top-down processing can be acutely dysregulated by BCAAs.