Abstract
Motivational salience plays an important role in shaping human behavior, but recent studies demonstrate that human performance is not uniformly improved by motivation. Instead, action has been shown to dominate valence in motivated tasks, and it is particularly difficult for humans to learn the inhibition of an action to obtain a reward, but the neural mechanism behind this behavioral specificity is yet unclear. In all mammals, including humans, the monoamine neurotransmitter dopamine is particularly important in the neural manifestation of appetitively motivated behavior, and the human dopamine system is subject to considerable genetic variability. The well-studied TaqIA restriction fragment length polymorphism (rs1800497) has previously been shown to affect striatal dopamine metabolism. In this study we investigated a potential effect of this genetic variation on motivated action/inhibition learning. Two independent cohorts consisting of 87 and 95 healthy participants, respectively, were tested using the previously described valenced go/no-go learning paradigm in which participants learned the reward-associated no-go condition significantly worse than all other conditions. This effect was modulated by the TaqIA polymorphism, with carriers of the A1 allele showing a diminished learning-related performance enhancement in the rewarded no-go condition compared to the A2 homozygotes. This result highlights a modulatory role for genetic variability of the dopaminergic system in individual learning differences of action-valence interaction.
Highlights
Efficient decision making requires an individual to select responses that maximize reward and minimize punishment or loss
In all mammals, including humans, the monoamine neurotransmitter dopamine is important in the neural manifestation of appetitively motivated behavior, and the human dopamine system is subject to considerable genetic variability
GENOTYPING Genotyping was performed in the entire cohort of 719 subjects, and two sub-cohorts were recruited based on the DRD2/ANKK1 TaqIA genotype
Summary
Efficient decision making requires an individual to select responses that maximize reward and minimize punishment or loss. Previous studies have shown that these two axes are not independent (GuitartMasip et al, 2012b, 2013; Cavanagh et al, 2013; Chowdhury et al, 2013; for review see Guitart-Masip et al, 2014) and that decision making is influenced by an instrumental controller that learns to optimize choices on the basis of their contingent consequences, and on a Pavlovian controller that generates stereotyped, “hard-wired” behavioral responses to the occurrence of motivationally salient outcomes or learned predictions of such outcomes (Dickinson and Balleine, 2002; Guitart-Masip et al, 2013) The presence of such “hard-wired” response patterns may be an evolutionarily beneficial adaptation to an environment world in which obtaining a reward typically requires some sort of overt behavioral response (go to win) whereas avoiding a punishment rather requires an avoidance of those actions that may lead to it (no-go to avoid losing). On the other hand, such a response bias may be a source of suboptimal behavior when Pavlovian and instrumental controllers are in opposition (Breland and Breland, 1961; Dayan et al, 2006; Boureau and Dayan, 2011).
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