Resting-state network connectivity in cognitively unimpaired drug-naive patients with rigidity-dominant Parkinson's disease

Background: Parkinson's disease (PD) could be classified into akinetic-rigidity (PDAR), tremor-dominant (PDTD) and mixed subtypes. PDAR patients are more prone to develop cognitive deficits. The default mode network (DMN), fronto-parietal network (FPN) and dorsal attention network (DAN) play important roles in cognitive processing. Our aim was to evaluate changes in connectivity patterns of the DMN, and its interrelation with the FPN and DAN in cognitively unimpaired drug-naive PDAR patients. Method: Resting-state functional MRI (rs-fMRI) data was collected in 20 cognitively unimpaired early-stage drug-naive PDAR patients and 20 age-, gender- and cognition- matched healthy controls (HCs). Group-level independent component analysis (ICA) was used to investigate changes in functional connectivity (FC) within the DMN between PDAR and HCs groups, and relationships between the DMN and FPN/DAN were evaluated by seed-based approach. Results: In PDAR patients, a significantly decreased FC, as compared with HCs, was observed in the left inferior parietal lobule (IPL) within the DMN. And the left IPL had a reduced FC with the left anterior cingulate cortex (ACC), left superior frontal gyrus (SFG), and left precuneus. However, no differences were detected in the FC between the left IPL and FPN/DAN. In addition, cognitive scores on the brief visuospatial memory test revised (BVMT-R), representing for cognitive memory domain, were positively correlated with the FC of the left IPL with bilateral SFG. Conclusions: Our study mainly revealed altered within-DMN connectivity in cognitively unimpaired PDAR patients, which could provide further insights into the mechanism underlying cognitive decline evolution in the PD subtype.