Effects of Parkinson's disease on cognitive action control: Insights on impulsive response tendencies using an oculomotor Simon task

Abstract

Objectives: Cognitive action control allows suppressing automatic activation and producing a controlled response when conflicts arise. This process is modulated by the basal ganglia and recent studies have shown that it was impaired in Parkinson's disease (PD). This study gives insights regarding the effect of PD on cognitive action and more precisely on impulsive responses. Methods: 40 patients with PD with no cognitive impairment and 40 healthy controls (HC) underwent an oculomotor Simon task in which they were required to make a leftward or rightward eye movement according to the color of a target and to ignore its location. The two dimensions of the stimuli created congruent (color and location activating the same response) and incongruent (color and location activating conflicting responses) trials. Results were analyzed using distributional analysis according to the activation-suppression model. Results: PD patients had a greater congruence effect on both reaction time and accuracy rate demonstrating a greater difficulty to resolve conflicts. Distributional analysis revealed that PD patients made more fast errors than HC. The rate of impulsive errors was further correlated to the Barrat Impulsiveness Scale (BIS) scores. When they responded slower, PD patients were also impaired compared to HC. Conclusions: Our results show that both the automatic and controlled routes involved in the cognitive action control are affected in PD. Furthermore, impulsive response tendencies in PD measured by a conflict task seems related to behavioral impulsivity. Therefore, conflict tasks could be used to further study impulsivity in PD and its ability to detect early troubles should be investigated