Functional Connectivity in Parkinson's Disease Patients with Mild Cognitive Impairment

To explore the alteration of pattens of anatomical and functional connectivity (FC) of posterior cingulate cortex (PCC) in Parkinson's disease (PD) patients with cognitive dysfunction and the relationship between the connection strengths and cognitive state.

We prospectively enrolled 20 PD patients with mild cognitive impairment (PD-MCI), 13 PD patients with normal cognition (PD-NC) and 13 healthy controls (HCs). By collecting, preprocessing and FC analyzing resting-state functional magnetic resonance imaging (rs-fMRI) data, we extracted default mode network (DMN) patterns, compared the differences in DMN between the three groups and the analyzed the correlation between FC value with the commonly used neuropsychological testing.

The PD-MCI showed significant worse performances in general cognition, and PD-NC and HCs showed comparable performances of cognitive function. Cognitive-related differences in DMN were detected in the bilateral precuneus (BPcu). Compared with the HCs, PD-NC and PD-MCI showed significantly decreased FC within BPcu (both P < 0.001). For PD-MCI, the rho of the Fisher's Z-transformed FC (zFC) value within BPcu with the TMTA, DSST and CFT-20min were 0.50, 0.66 and 0.47, respectively. For PD-NC, the rho of the zFC value within BPcu with the MMSE was 0.58.

BPcu was the cognitive-related region in DMN. As cognition declines, FC within BPcu weakens. For PD-MCI, the higher the FC values within BPcu were likely to be related to the better the performances of TMTA, DSST and CFT-20 min DR, which needs to be further confirmed by large-sample studies.