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Abstract
The process of decision-making involves the complex interaction of several neuroanatomical structures and neurotransmitter systems. Research has implicated the intricate role of the dopaminergic pathway system in the role of decision-making processes. Additionally, recent research has demonstrated a new procedural method to adequately manipulate the dopaminergic pathway system through the administration of an amino acid depleted mixture lacking phenylalanine and tyrosine, the precursors to dopamine synthesis. The purpose of the present study was to investigate the effects of the dopaminergic system on measures of decision-making through the utilization of this recently developed amino acid manipulation procedure. The study employed a double-blind, randomized, between-groups design with a total of 48 participants who received either an amino acid depleted mixture or an amino acid balanced control mixture. Decision-making was examined using three behavioral performance-based measures of decision-making, the Bechara Gambling Task (BGT), Balloon Analogue Risk Task (BART), and the Stoplight Task (SLT). It was hypothesized that alterations in dopamine synthesis, specifically lowering of dopamine synthesis through the administration of the amino acid manipulation procedure would contribute to alterations in decision-making processes or a decline in risky decisions on the three behavioral measures. Results partially supported hypotheses. There were no significant group differences on the overall scores for the three behavioral measures of decision-making, but there was a significant group difference when looking at performance on the BGT on a trial-by-trial basis. This result suggests that as participants learned the task over time, there was a tendency for individuals who consumed the amino acid depleted mixture to shift preference to the more advantageous decks at an increasing rate as compared to the individuals who consumed the amino acid balanced control mixture. Despite some limitations, the current study serves as a starting point for future research into the role of dopaminergic systems in the process of decision-making as well as the differentiation of decision-making processes as indicated by three behavioral measures.
