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Published June 26, 2018 | Submitted + Published + Supplemental Material
Journal Article Open

An effect of serotonergic stimulation on learning rates for rewards apparent after long intertrial intervals

Abstract

Serotonin has widespread, but computationally obscure, modulatory effects on learning and cognition. Here, we studied the impact of optogenetic stimulation of dorsal raphe serotonin neurons in mice performing a non-stationary, reward-driven decision-making task. Animals showed two distinct choice strategies. Choices after short inter-trial-intervals (ITIs) depended only on the last trial outcome and followed a win-stay-lose-switch pattern. In contrast, choices after long ITIs reflected outcome history over multiple trials, as described by reinforcement learning models. We found that optogenetic stimulation during a trial significantly boosted the rate of learning that occurred due to the outcome of that trial, but these effects were only exhibited on choices after long ITIs. This suggests that serotonin neurons modulate reinforcement learning rates, and that this influence is masked by alternate, unaffected, decision mechanisms. These results provide insight into the role of serotonin in treating psychiatric disorders, particularly its modulation of neural plasticity and learning.

Additional Information

© 2018 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received 04 December 2017; Accepted 22 May 2018; Published 26 June 2018. We thank the Gatsby Charitable Foundation, the Joint Initiative on Computational Psychiatry and Ageing Research between Max Planck Society and UCL, the Japan Society for the Promotion of Science, the European Research Council (250334 and 671251), Fundação para a Ciência e a Tecnologia (PD/BD/52446/2013 and SFRH/BPD/46314/2008), and the Champalimaud Foundation for generous support. Author Contributions: K.I., M.S.F., M.M., Z.F.M., and P.D. conceived the project. M.S.F., M.M., and Z.F.M. designed and performed the original experiments. K.I. and P.D. developed computational models, designed and performed analysis with inputs from M.S.F., M.M., and Z.F.M. K.I., M.S.F., M.M., Z.F.M., and P.D. discussed the results and wrote the manuscript. The authors declare no competing interests. Data availability: The data and codes that support the findings of this study are available from the corresponding author on reasonable request.

Attached Files

Published - s41467-018-04840-2.pdf

Submitted - 215400.full.pdf

Supplemental Material - 41467_2018_4840_MOESM1_ESM.pdf

Supplemental Material - 41467_2018_4840_MOESM2_ESM.pdf

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Created:
August 19, 2023
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