In the auditory system, one of the strongest indices of sensory dysfunction is impaired generation of an event related potential (ERP) component termed mismatch negativity (MMN). MMN generation is impaired in schizophrenia and has been strongly linked to the NMDA system. The roles of the dopaminergic and the serotonergic systems in MMN generation were further explored in an investigation [11] of the effects of acutely depleting dopamine and serotonin [5-hydroxytryptamine or 5-hydroxytryptophan (5-HT)] in 16 healthy participants. A double-blind, placebo-controlled, crossover design was used, and individuals were tested in MMN under four acute-treatment conditions separated by a 5-day washout period: balanced amino acid control (no depletion), tyrosine/phenylalanine depletion (to reduce dopamine neurotransmission), tryptophan depletion (to reduce 5-HT neurotransmission), and combined tryptophan/tyrosine/phenylalanine depletion. There was no main effect of amino acid depletion on MMN amplitudes or latencies, suggesting that acute modulation of the dopaminergic and serotonergic systems does not lead to changes in MMN.
