Effects of dopaminergic medication on reward and punishment sensitivity in risky decision-making

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Pathological gambling (PG) is a behavioural addiction similar in many aspects to substance use disorder (Clark & Limbrick-Oldfield, 2014). PG involves excessive risk taking and (monetary) reward. Neurotransmitter dopamine is of interest in relation to risk taking and PG due to its central role in learning from reward and punishment (Cools et al., 2009). Moreover, some Parkinson’s disease patients develop PG following dopamine replacement therapy (Clark & Dagher, 2014). The aim of this study was to examine the effects of dopaminergic modulation on risk-taking behaviour in healthy and PG individuals. Dopamine D2/D3 receptor antagonist sulpiride and a placebo drug were administered in order to transiently alter dopamine transmission during an economic decision-making task. Participants chose between sure choices of winning (or losing) a certain amount of money and gambles with different probabilities to win (or lose) money. A prospect theory (Kahneman & Tversky, 1979) modelling approach was used to estimate parameters reflecting sensitivity to outcomes and probabilities and optimism about risk, based on the varying amounts of money and probabilities in the task. We found that sulpiride decreased distortion in weighting the probabilities of potential gains. That is, participants overweighted low and underweighted moderate to high winning probabilities less under sulpiride compared with placebo. However, the drug effect did not differ between the groups and was not found in the loss domain. In conclusion, we found evidence for a relationship between dopamine and risky decision-making in the distortion of probability weighting.
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