Effects of dopamine on reinforcement learning and consolidation in Parkinson’s disease

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Abstract

Emerging evidence suggests that dopamine may modulate learning and memory with important implications for understanding the neurobiology of memory and future therapeutic targeting. An influential hypothesis posits that dopamine biases reinforcement learning. More recent data also suggest an influence during both consolidation and retrieval. Eighteen Parkinson’s disease patients learned through feedback ON or OFF medication with memory tested 24 hours later ON or OFF medication (4 conditions, within-subjects design with matched healthy control group). Patients OFF medication during learning decreased in memory accuracy over the following 24 hours. In contrast to previous studies, however, dopaminergic medication during learning and testing did not affect expression of positive or negative reinforcement. Two further experiments were run without the 24-hour delay, but they too failed to reproduce effects of dopaminergic medication on reinforcement learning. While supportive of a dopaminergic role in consolidation, this study failed to replicate previous findings on reinforcement learning.

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John P Grogan

Institute of Clinical Neurosciences, School of Clinical Sciences, University of Bristol, Bristol, United Kingdom

For correspondence
john.grogan@bristol.ac.uk

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-0463-8904
Demitra Tsivos

Clinical Neurosciences, North Bristol NHS Trust, Bristol, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Laura Smith

Institute of Clinical Neurosciences, School of Clinical Sciences, University of Bristol, Bristol, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Brogan E Knight

Clinical Neurosciences, North Bristol NHS Trust, Bristol, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Rafal Bogacz

Medical Research Council Brain Network Dynamics Unit, University of Oxford, Oxford, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Alan Whone

Institute of Clinical Neurosciences, School of Clinical Sciences, University of Bristol, Bristol, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Elizabeth J Coulthard

Institute of Clinical Neurosciences, School of Clinical Sciences, University of Bristol, Bristol, United Kingdom

For correspondence
elizabeth.coulthard@bristol.ac.uk

Competing interests
The authors declare that no competing interests exist.

Funding

Wellcome (PhD Studentshipt SJ1102)

John P Grogan

BRACE (Project grant)

John P Grogan
Elizabeth J Coulthard

Medical Research Council (MC UU 12024/5)

Rafal Bogacz

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Human subjects: Ethical approval was obtained from the NHS Research Ethics Committee at Frenchay, Bristol (09/H0107/18). All participants gave written consent, in accordance with the Declaration of Helsinki.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.