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Gilger MD, Hellrung L, Neukam PT, Kroemer NB, Nebe S, Pooseh S, Deza-Lougovski YI, Smolka MN. Arbitration between model-free and model-based control is not affected by transient changes in tonic serotonin levels. J Psychopharmacol 2024; 38:178-187. [PMID: 38151862 PMCID: PMC10863371 DOI: 10.1177/02698811231216325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
BACKGROUND Serotonin has been suggested to modulate decision-making by influencing the arbitration between model-based and model-free control. Disruptions in these control mechanisms are involved in mental disorders such as drug dependence or obsessive-compulsive disorder. While previous reports indicate that lower brain serotonin levels reduce model-based control, it remains unknown whether increases in serotonergic availability might thus increase model-based control. Moreover, the mediating neural mechanisms have not been studied yet. AIM The first aim of this study was to investigate whether increased/decreased tonic serotonin levels affect the arbitration between model-free and model-based control. Second, we aimed to identify the underlying neural processes. METHODS We employed a sequential two-stage Markov decision-task and measured brain responses during functional magnetic resonance imaging in 98 participants in a randomized, double-blind cross-over within-subject design. To investigate the influence of serotonin on the balance between model-free and model-based control, we used a tryptophan intervention with three intervention levels (loading, balanced, depletion). We hypothesized that model-based behaviour would increase with higher serotonin levels. RESULTS We found evidence that neither model-free nor model-based control were affected by changes in tonic serotonin levels. Furthermore, our tryptophan intervention did not elicit relevant changes in Blood-Oxygenation-Level Dependent activity.
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Affiliation(s)
- Maximilian D. Gilger
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
| | - Lydia Hellrung
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
- Zurich Center for Neuroeconomics, Department of Economics, University of Zurich, Zurich, Switzerland
| | - Philipp T. Neukam
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
- Depression and Anxiety Center for Discovery and Treatment, Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Nils B. Kroemer
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
- Section of Medical Psychology, Department of Psychiatry and Psychotherapy, Faculty of Medicine, University of Bonn, Bonn, Germany
- Department of Psychiatry and Psychotherapy, Tübingen Center for Mental Health, University of Tübingen, Tübingen, Germany
- German Center for Mental Health (DZPG), Tübingen, Germany
| | - Stephan Nebe
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
- Zurich Center for Neuroeconomics, Department of Economics, University of Zurich, Zurich, Switzerland
| | - Shakoor Pooseh
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
- Freiburg Center for Data Analysis and Modelling, Institute of Physics, University of Freiburg, Freiburg, Germany
| | - Yacila I. Deza-Lougovski
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
- Institute of Psychology, University of the Bundeswehr München, Neubiberg, Germany
| | - Michael N. Smolka
- Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Dresden, Germany
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