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Valence-dependent influence of serotonin depletion on model-based choice strategy.

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Worbe, Y 
Palminteri, S 
Savulich, G 
Daw, ND 
Fernandez-Egea, E 


Human decision-making arises from both reflective and reflexive mechanisms, which underpin goal-directed and habitual behavioural control. Computationally, these two systems of behavioural control have been described by different learning algorithms, model-based and model-free learning, respectively. Here, we investigated the effect of diminished serotonin (5-hydroxytryptamine) neurotransmission using dietary tryptophan depletion (TD) in healthy volunteers on the performance of a two-stage decision-making task, which allows discrimination between model-free and model-based behavioural strategies. A novel version of the task was used, which not only examined choice balance for monetary reward but also for punishment (monetary loss). TD impaired goal-directed (model-based) behaviour in the reward condition, but promoted it under punishment. This effect on appetitive and aversive goal-directed behaviour is likely mediated by alteration of the average reward representation produced by TD, which is consistent with previous studies. Overall, the major implication of this study is that serotonin differentially affects goal-directed learning as a function of affective valence. These findings are relevant for a further understanding of psychiatric disorders associated with breakdown of goal-directed behavioural control such as obsessive-compulsive disorders or addictions.



Adult, Appetitive Behavior, Choice Behavior, Diet, Double-Blind Method, Factor Analysis, Statistical, Female, Humans, Male, Models, Psychological, Neuropsychological Tests, Punishment, Reward, Serotonin, Tryptophan

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Mol Psychiatry

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Springer Science and Business Media LLC
Medical Research Council (G0001354)
Medical Research Council (G1000183)
Medical Research Council (MR/J012084/1)
Wellcome Trust (089589/Z/09/Z)
Wellcome Trust (093875/Z/10/Z)
Wellcome Trust (104631/Z/14/Z)
This research was funded by Wellcome Trust Grants awarded to VV (Intermediate WT Fellowship) and Programme Grant (089589/Z/09/Z) awarded to TWR, BJE, ACR, JWD and BJS. It was conducted at the Behavioural and Clinical Neuroscience Institute, which is supported by a joint award from the Medical Research Council and Wellcome Trust (G00001354). YW was supported by the Fyssen Foundation. SP is supported by Marie Curie Intra-European Fellowship (FP7-People-2012-IEF).