Research

Computational Psychiatry & Decision-making

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Abstracts

  • doi pdf Differential, but not opponent, effects of L-DOPA and citalopram on action learning with reward and punishment
  • Guitart-Masip M, Economides, Huys QJM, Frank MJ, Chowdhury R, Düzel E, Dayan P and Dolan RJ
  • Psychopharmacology (2013): 231:955-966.
  • Background: Decision-making involves two fundamental axes of control namely valence, spanning reward and punishment, and action, spanning invigoration and inhibition. We recently used a task whose contingencies explicitly decouple valence and action to show that these axes are inextricably coupled during learning. This results in a disadvantage in acquiring active choices in punished conditions and passive choices in rewarded conditions. The neuromodulators dopamine and serotonin are likely to play a role in these asymmetries. Dopamine signals anticipation of future rewards and is involved in an invigoration of motor responses leading to reward. Serotonin is associated with motor inhibition and punishment processing. Methods: Here we combined computational modelling with a pharmacological manipulation of dopamine and serotonin to examine acquisition of instrumental responding in a task that crosses action (go/no go) with valence (reward/punishment) in healthy human volunteers. Results: Contrary to expectation we found that levodopa decreased the coupling of action and valence that was evident in the placebo and citalopram groups. Citalopram had distinct effects and increased participants tendency to perform active responses independent of outcome valence, consistent with decreased motor inhibition. Conclusion: The current data highlights the importance of orthogonally manipulating action requirements and outcome valence if one wants to reveal the full complexity of the roles played by dopamine and serotonin in instrumental learning.