Genetic triple dissociation reveals multiple roles for dopamine in reinforcement learning:
...Here, we show with genetic analyses that three independent dopaminergic^ mechanisms contribute to reward and avoidance learning in humans.^ A polymorphism in the DARPP-32 gene, associated with striatal^ dopamine function, predicted relatively better probabilistic^ reward learning. Conversely, the C957T polymorphism of the DRD2^ gene, associated with striatal D2 receptor function, predicted^ the degree to which participants learned to avoid choices that^ had been probabilistically associated with negative outcomes.^ The Val/Met polymorphism of the COMT gene, associated with prefrontal^ cortical dopamine function, predicted participants' ability^ to rapidly adapt behavior on a trial-to-trial basis. These findings^ support a neurocomputational dissociation between striatal and prefrontal dopaminergic mechanisms in reinforcement learning. Computational maximum likelihood analyses reveal independent gene effects on three reinforcement learning parameters that can explain the observed dissociations.
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