Dopamine D2 receptor antagonism modulates antidepressant placebo effects on reward sensitivity in healthy participants

Content: Open code and data for the manuscript "Augustat, N., Lee, E., Ahn, W. Y., Chuang, L. C., Endres, D., Mueller, E.: Dopamine D2 receptor antagonism modulates antidepressant placebo effects on reward sensitivity in healthy participants". Instructions can be found in the file "readme.txt", and a preprint in the file "RL_Manuscript.tar". Summary: The data set consists of 272 participants allocated in a 2x2 between-subjects design (expectation: high/low, substance: placebo/sulpiride 400mg) who performed a probabilistic selection task. We fit a total of 74 hierarchical Bayesian reinforcement learning models with different sets of parameters to participants' choice data and conducted a model comparison, including recovery checks, across all models. The winning model consisted of three parameters (learning rate, inverse temperature, forgetting rate) and yielded an increase in learning rates under high expectations in the placebo group but not in the sulpiride group. Higher learning rates may indicate an increase in reward sensitivity, suggesting an expectation-induced improvement in reward sensitivity. Sulpiride 400mg blocked this effect, supporting a modulatory role of dopamine.