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Pramipexole Enhances Reward Learning by Preserving Value Estimates.

Authors
  • Halahakoon, Don Chamith1
  • Kaltenboeck, Alexander2
  • Martens, Marieke3
  • Geddes, John G1
  • Harmer, Catherine J1
  • Cowen, Philip1
  • Browning, Michael4
  • 1 Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health National Health Service Foundation Trust, Warneford Hospital, Oxford, United Kingdom. , (United Kingdom)
  • 2 Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Clinical Division of Social Psychiatry, Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria. , (Austria)
  • 3 Department of Psychiatry, University of Oxford, Oxford, United Kingdom. , (United Kingdom)
  • 4 Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health National Health Service Foundation Trust, Warneford Hospital, Oxford, United Kingdom. Electronic address: [email protected]. , (United Kingdom)
Type
Published Article
Publication Date
Feb 01, 2024
Volume
95
Issue
3
Pages
286–296
Identifiers
DOI: 10.1016/j.biopsych.2023.05.023
PMID: 37330165
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Dopamine D2-like agonists show promise as treatments for depression. They are thought to act by enhancing reward learning; however, the mechanisms by which they achieve this are not clear. Reinforcement learning accounts describe 3 distinct candidate mechanisms: increased reward sensitivity, increased inverse decision-temperature, and decreased value decay. As these mechanisms produce equivalent effects on behavior, arbitrating between them requires measurement of how expectations and prediction errors are altered. We characterized the effects of 2 weeks of the D2-like agonist pramipexole on reward learning and used functional magnetic resonance imaging measures of expectation and prediction error to assess which of these 3 mechanistic processes were responsible for the behavioral effects. Forty healthy volunteers (50% female) were randomized to 2 weeks of pramipexole (titrated to 1 mg/day) or placebo in a double-blind, between-subject design. Participants completed a probabilistic instrumental learning task before and after the pharmacological intervention, with functional magnetic resonance imaging data collected at the second visit. Asymptotic choice accuracy and a reinforcement learning model were used to assess reward learning. Pramipexole increased choice accuracy in the reward condition with no effect on losses. Participants who received pramipexole had increased blood oxygen level-dependent response in the orbital frontal cortex during the expectation of win trials but decreased blood oxygen level-dependent response to reward prediction errors in the ventromedial prefrontal cortex. This pattern of results indicates that pramipexole enhances choice accuracy by reducing the decay of estimated values during reward learning. The D2-like receptor agonist pramipexole enhances reward learning by preserving learned values. This is a plausible mechanism for pramipexole's antidepressant effect. Copyright © 2023 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

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