Decision making in Parkinson’s disease: A preliminary study investigating the influence of dopamine replacement therapy on decisional processes in patients affected by Parkinson’s disease

Parkinson’s disease (PD) is a neurodegenerative disease, mainly due to a loss of dopaminergic neurons in the substantia nigra, causing motor and non-motor symptoms. As the disease progresses, cortical regions and corticostriatal pathways are involved. Literature suggests that PD patients may display a propensity for making risky value-based decisions. This is due, at least in part, to the pathophysiological features of PD that involves neural structures supporting decisional processes (e.g., evaluating choice options assigning subjective values, processing reward-or-loss consequences), where dopamine and corticostriatal circuits are pivotal. It is hypothesized that dopaminergic medications may affect decision-making toward risky choices. The study aimed at investigating relationships between decision-making under ambiguous and risky conditions and dopaminergic therapy. Analyses involved 22 patients affected by idiopathic PD (10 males, age: 65.3 ± 6.78, education: 10.5 ± 3.95). Inclusion criteria were the absence of impulse control disorders and major cognitive impairments, and stable pharmacological treatment for at least two months. Participants underwent an assessment of decisional abilities under ambiguity and risk through the Iowa Gambling Task (IGT) and the Game of Dice (GDT), respectively. The medication regimens were recorded for each type of drug (i.e., levodopa, dopamine agonists, MAO-B inhibitor) and converted into Levodopa equivalent daily dosages (LEDDs). Data were analyzed through non-parametric statistics. Results showed negative correlations between LEDD of dopamine agonists and IGT (total gain: ρs = −.438; second block netscore: ρs = −.489) and between LEDD of levodopa and GDT (netscore: ρs = −.424; number of safe choices: ρs = −.459) (p<.05). No correlations emerged between decisional tasks and LEDD of MAO-B inhibitors or total LEDD. Findings supported a possible role played by levodopa and dopamine agonists in value-based decision-making, biasing decisional processes toward risky options. As well, findings can support the presence of different cognitive mechanisms underlying decision-making under ambiguity and risk.