Objective: We aimed to explore different aspects of action control, assessing reward-related behaviour, inhibition (externally and internally triggered) and sense of agency in Parkinson’s disease (PD) patients, with and without impulsive-compulsive behaviours (ICB) compared to a group of healthy subjects.

Background: Pathophysiology of ICB in PD is poorly understood. Most previous research focussed on reward-related processing in the brain. However, other aspects of volitional control of action may be important in the pathophysiology of ICB, such as sense of agency for action and action inhibition.

Methods: Thirty-eight PD patients (19 with and 19 without ICB) and 19 healthy subjects (HS) were included in the study. Subjects underwent a short test battery covering key components of voluntary action, including: Intentional Binding task which measures experience of agency; the Marble task, which measures the sequential balance between action and inhibition in intentional self-control; Stop signal reaction time which measures capacity for reactive inhibition; Balloon Analog Risk Task which measures reward sensitivity by titrating reward against risk.

Results: When comparing the degree of binding effects among groups, one way ANOVA showed a significant main effect of group for action binding (p= 0.004, F=6.27). Post hoc analysis revealed that PD-ICB showed significantly stronger action binding than HS (p=0.004), and than PD-no-ICB (p=0.04) [figure1]. There was no difference between PD-no-ICB and HS. A significant difference between PD-no-ICB and HC was detected in quantile SSRT (p=0.008). No other significant differences were found among groups in the other tasks.

Conclusions: PD patients with ICB have abnormal performance on a task of action binding compared to PD patients without ICB and healthy subjects. They appear to have a weak experience of their own volitional actions. They had no deficit on tasks evaluating externally and internally triggered inhibitory control, or in reward-based decision-making. Thus, we conclude that PD patients with ICB have a deficit in action representation at the cognitive/experiential level. This result opens new perspective on the pathophysiological basis of ICB deficits, and on the future therapeutic management of them.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/volition-and-action-control-in-parkinsons-disease-patients-with-impulsive-compulsive-behaviour-disorders/