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

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.