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Abstract
Despite interest within the scientific community in the neurotransmitter dopamine's role in emotion-based decision-making, few reports of the effects of dopamine manipulations are available in this area. This study aims to investigate dopamine's role in emotion-based decision-making through a common measure of this construct, the Iowa Gambling Task (IGT), using Acute Tyrosine & Phenylalanine Depletion (ATPD), a putative means of dopamine depletion in healthy adults. Here N=40 participants were randomized to either the ATPD group or a balanced control group prior to completing a battery of neuropsychological tests including the IGT, as well as pre- and post-manipulation blood draws for the hormone prolactin. IGT performance was analyzed with respect to two hypothesized roles of dopamine—motivated incentive responding and modulation of cognitive stability and flexibility. Both conventional and novel analytic strategies were applied due to recent critiques of the standard IGT analytic techniques as potentially insensitive. Novel strategies included (1) utilizing two rationally-derived punishment events instead of task blocks to divide the task for analyses; and (2) examining the frequency of switching between alternatives. The results indicated that the ATPD group's response latencies to risky alternatives were subtly more adaptive than those of the balanced group. Modulation of latencies to risky alternatives predicted total score for the ATPD group only, while latencies for safe alternatives related to total score for the balanced group only. Further, the ATPD group switched between certain alternatives with a greater frequency than did the balanced group. The results could be construed as evidence of dopamine's role in modulating both incentive salience and the cognitive stability/flexibility trade-off. Results are discussed with respect to these hypothesized roles of dopamine in emotion-based decision-making and with respect to the utility of the proposed novel analytic strategies.
