Decisions, Decisions: The Neurobiology of the effects of Dopamine Replacement Therapy on Decision-Making in Parkinson’s Disease

Julie Lee

doi:10.5334/jeps.cv

Abstract

Dopamine replacement therapy (DRT) alleviates motor symptoms in Parkinson’s disease but induces neuropsychiatric side-effects. This review evaluates recent research into the decision-making deficits caused by DRT arising because dopamine ‘overdoses’ a relatively-intact ventral striatum while replenishing the dorsal striatum. Consequently, patients on medication are worse at learning from losses but better at learning from wins than healthy controls. Additionally, due to greater disruption of medication on limbic than cognitive neural circuits, patients are poorer at decision-making under risk than decision-making under ambiguity. Particularly, task components related to ventral fronto-striatal and orbitofrontal regions are affected more than those related to dorsal and prefrontal regions. Selective deficits in feedback processing and outcome evaluation due to limbic overdose likely drive this effect.

Highlights

Dopamine replacement therapy (DRT) alleviates motor symptoms in Parkinson’s disease but induces neuropsychiatric side-effects
A DRT-induced hyperdopaminergic state in the ventral striatum of Parkinson’s disease (PD) patients could hinder reward-processing, including the ability to learn from negative decision outcomes (Weintraub, 2008)
Reward-processing deficits in PD are most likely a result of the selective effect of DRT acting on the ventral striatum and interconnected regions such as the orbitofrontal cortex (OFC)

Summary

Introduction

Dopamine replacement therapy (DRT) alleviates motor symptoms in Parkinson’s disease but induces neuropsychiatric side-effects. The review will evaluate the role of dopamine replacement therapy in driving poor decision-making, focusing on selective impairments in feedback processing and outcome evaluation. Parkinson’s disease patients off medication show decision-making deficits as well, but the pattern is different to the effects of medication discussed below (Wiecki & Frank, 2010). A DRT-induced hyperdopaminergic state in the ventral striatum of PD patients could hinder reward-processing, including the ability to learn from negative decision outcomes (Weintraub, 2008).

Results

Conclusion