Objective: To investigate whether 3 different domains of impulsive behavior(reactive, proactive and cognitive) are differentially affected in medicated PD as compared with healthy controls. We also aimed to understand the putative role of dopamine agonists in the dysregulation of inhibitory programs leading to impulsive behavior.

Background: Impulsivity in PD is common even in patients without Impulse control disorders. Two major types of impulsivity as been isolated: cognitive and motor impulsivity(divided in reactive and proactive). As far as we know these different domains were never analyzed together in PD.

Methods: PD patients were compared with healthy controls matched for age and education. PD patients were assessed in ON and OFF medication states. Demographics, motor score(UPDRS-III), cognition(MoCA), depressive symptoms(BDI-II) and apathy(AES) were prospectively collected. All PD patients were on DRT. Three computerized tasks were used to assess impulsivity: 1)Go/NoGo(GNG), to assess the reactive impulsivity domain; 2)the AX Continuous Performance Task (AX-CPT), to assess both the reactive and proactive domains; 3)the Ballon Analogue Risk Taking(BART) task, to study the cognitive domain of impulsivity. Patients with cognitive impairment, apathy or depression were excluded.

Results: Twenty-one PD patients, 11 on levodopa/carbidopa(PD-l), and 10 on levodopa/carbidopa plus dopamine agonist(PD-l/da) and 13 healthy controls were included. PD patients committed a higher number of commission errors(CE) in the GNG task when compared to controls(p<0.025), and more post punition pumps errors in the BART task(p<0.018) in ON state but not in OFF state. In AX-CPT, no main effect was found for the ON state(p>0.11), but PD patients in OFF state experienced a higher number of A cue errors compared to healthy controls(p<0.012). PD-l/da patients made significantly more CE than PD-l (p<0.040). For the AX-CPT, PD-l/da made more A cue errors than PD-l(p<0.012). PD-l/da made more CE during the ON state compared to the OFF state(p<0.048).

Conclusions: This study showed that the domains of reactive and cognitive impulsivity domain are preferentially affected in medicated PD. The sensitivity of the cognitive reward system to punition contingencies is absent in the OFF state. Dopamine agonists appear to further disrupt impulse control when compared with patients on levodopa/carbidopa monotherapy.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neurocognitive-domains-of-impulsivity-in-parkinsons-disease-pd-and-the-effects-of-dopaminergic-replacement-therapy-drt/