Effects of levodopa therapy on voxel-based degree centrality in Parkinson's disease

Levodopa therapy is widely recognized as an effective treatment for PD patients, however, it is rare of the study looking at effects of levodopa therapy on the whole-brain network. This study was to evaluate the effects of levodopa on whole-brain degree centrality (DC) and seed-based functional connectivity (FC) in PD patients. We recruited 26 PD patients and acquired their resting-state fMRI data before ('OFF' state) and after ('ON' state) taking a dose of 400 mg levodopa. Through constructing the voxel-based brain functional network, we calculated distant and local DC and seed-based FC. We found that compared to the healthy controls, the PD patients at 'OFF' state showed significantly decreased distant DC in several occipital regions and left postcentral gyrus, but increased distant DC in the right precentral gyrus, supplementary motor area, and several frontal regions. Meanwhile, we detected decreased local DC in the left cuneus and bilateral insula but increased local DC in several temporal regions in the PD patients at 'OFF' state compared to the controls. Using paired-sample t-tests, we found that levodopa effectively normalized the distant DC abnormalities in the PD patients particularly in the occipital regions and postcentral gyrus. Additionally, compared to 'OFF' state, the PD patients at 'ON' state showed decreased FC of the left median cingulate gyrus to brain regions in default mode network. The decreased FC of the left median cingulate gyrus to right temporal pole was associated with improved UPDRS-III score. This study provided new evidence for understanding the neural effects of levodopa therapy on the whole-brain network in PD patients.