Dopaminergic medication improves cognitive control under low cognitive demand in Parkinson's disease

Dopamine agonists are the main pharmacological intervention for the motor symptoms of Parkinson's disease (PD). However, dopaminergic medication has been associated with disinhibitory psychopathology in some patients. The aim of this study was to test the effect of dopaminergic medication on inhibitory control in patients with PD using the paced Random Number Generation task (RNG), which requires inhibition of prepotent counting in series to produce a random sequence of numbers.

Twenty-three PD patients performed RNG on and off dopaminergic medication. Cognitive load was manipulated by performing RNG at faster (1Hz) and slower (0.5 Hz) rates. For RNG, two scores (CS1 and CS2) were derived, which are considered indices of more automatic and more controlled counting, respectively.

There were no main effects of medication on RNG performance. There was a significant main effect of cognitive load on CS1, with higher CS1 scores at the faster rate (p = <.01). A significant interaction effect between medication and rate (cognitive load; p = .03) followed by post hoc testing, revealed that CS2 scores were higher, on medication, at the slower but not the faster rate.

Patients with PD displayed increased use of more controlled processing strategies on medication at the slowest rate of RNG. Therefore, while dopaminergic medication has been associated with disinhibitory psychopathology, our results suggest that dopamine therapy may enhance some forms of inhibitory cognitive control in PD, but only if there is sufficient time to engage controlled processing strategies. (PsycInfo Database Record (c) 2020 APA, all rights reserved).