Objective: To compare the influence of levodopa and subthalamic nucleus stimulation (STN-DBS) on effort-based decision-making in Parkinson’s disease (PD).

Background: Idiopathic PD is a neurodegenerative disorder entailing several behavioural dysfunctions. It is now well admitted that Levodopa and, in more advanced PD, high-frequency STN-DBS, influence motivated behaviours. The aim of the present work was to determine the influence of STN-DBS, Levodopa and the association of both treatments on effort- and reward-based decision-making.

Methods: We recruited 13 PD patients and 13 matched healthy controls (HC). Our experimental task involved taking a decision based on variable rewards (3 levels) and efforts (12 levels). If the participants judged that the reward was worth realising the effort, they had to squeeze a dynamometer with the necessary force. All PD patients completed the task in 4 conditions: without treatment, with Levodopa or STN-DBS alone, with both Levodopa and STN-DBS. Using mixed model, we analysed the acceptance rate, decision time and applied force on the dynamometer.

Results: Our results showed a decrease of acceptance rate and applied force for PD patients without treatment in comparison to HC. Taken alone, Levodopa induced no changes in comparison to the condition without treatment. In contrast, STN-DBS, either with and without Levodopa, improved all measures, leading to an undistinguishable profile from HC.

Conclusions: From our results, we can conclude that Levodopa remains insufficient for cost-benefit computation. In contrast, STN-DBS modifies decision-making processes by normalising all our measures. We can hypothesise that STN-DBS, but not Dopamine, helps to restore the integration of information from cortical territories involved in both reward and effort valuations.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/subthalamic-nucleus-stimulation-normalises-effort-based-decision-making-in-parkinsons-disease/