Abnormal resting-state functional connectivity in posterior cingulate cortex of Parkinson's disease with mild cognitive impairment and dementia.

Objective: To investigate changes in the functional connectivity (FC) pattern in the posterior cingulate cortex (PCC) of Parkinson's disease (PD) patients with mild cognitive impairment and dementia by employing resting-state functional magnetic resonance imaging (RS-fMRI).

Methods: Twenty-seven PD patients with different cognitive status and 9 healthy control subjects (control group) were enrolled for RS-fMRI. The RS-fMRI data were analyzed with DPARSF and REST software. Regions with changed functional connectivity were determined by the seed-based voxelwise method and compared between groups. Correlation between the intensity of FC and the MoCA scores of PD group was analyzed.

Results: Parametric maps showed statistical increases in PCC functional connectivity in PD-MCI patients and decreases in PCC connectivity in PDD patients. The latter group of patients also showed evidence for increased connectivity between prefrontal cortices and posterior cerebellum. A significant positive correlation was found between the MoCA scores and the strength of PCC connectivity in the angular gyrus and posterior cerebellum and a negative correlation between MoCA scores and PCC connectivity in all other brain regions.

Conclusion: When patients transition from PD-NCI to PD-MCI, there appears to be an increase in functional connectivity in the PCC, suggesting an expansion of the cortical network. Another new network (a compensatory prefrontal cortical-cerebellar loop) later develops during the transition from PD-MCI to PDD.