The Effects of Levodopa on Cognitive Control in Parkinson's Disease.

The present study aimed to compare brain activity changes related to proactive and reactive control strategies in patients with Parkinson’s disease during “On” levodopa and “Off” levodopa conditions. The study consisted of two participants who had received a prior diagnosis of Parkinson’s Disease. The participants completed AX-CPT task as a measure of attention control in two sessions: a) “On Levodopa” and b) “Off Levodopa” while they were in the fMRI scanner. Prior to the analysis, the T1- weighted anatomical scan images and the BOLD multiband functional images of both the participants were BIDS (Brain Imaging Data Structure) validated and preprocessed using the standard FMRIPrep pipeline. The imaging data was then analyzed using SPM12 (Statistical parametric mapping) software. Individual-level analysis of the imaging data was conducted by creating General Linear models for both the participants on “ON” and “OFF” levodopa conditions. The BOLD responses were compared using AY>BY and BX > BY contrasts. Where BX >, BY contrast, measured BOLD activity related to reactive control strategy and AY> BY contrast measured BOLD activity related to the proactive control strategy. It was observed that participants tended towards reactive control strategy in both “On” and “Off” levodopa conditions.