Changes of default mode network in amnestic mild cognitive impairment: Evidence from PCC functional connectivity

Objective: To investigate the changes of posterior cingulate cortex (PCC) functional connectivity in amnestic mild cognitive impairment (aMCI). Methods: Eighteen patients of aMCI (aMCI group) and 20 healthy elderly (healthy elderly group) were enrolled, and the age, education level and sex were matched between two groups. Resting state fMRI was performed on all the subjects with GRE-EPI. Correlation analysis between PCC and all the other voxels in the brain was performed with a voxel-wise manner. Results: In aMCI group, bilateral dorsolateral prefrontal cortex (DLPFC), left medial prefrontal cortex (MPFC) and anterior cingulate cortex (ACC), bilateral inferior parietal lobule (IPL), bilateral middle temporal gyrus and precuneus showed significant functional connectivity to PCC. In healthy elderly group, areas showing significant functional connectivity to PCC included DLPFC, right MPFC and ACC, bilateral IPL, bilateral middle and inferior temporal gyrus, as well as bilateral precuneus. Multiple areas including superior/middle frontal gyrus, inferior frontal gyrus (p.Opercularis/p.Triangularis), MPFC/ACC, middle temporal gyrus in right hemisphere, as well as left precuneus, showed increased functional connectivity to PCC in healthy elderly group compared to aMCI group. Meanwhile, a series of brain areas, including middle cingulate cortex, superior parietal lobule (SPL), IPL, middle temporal gyrus in the left hemisphere, as well as right SPL, showed increased functional connectivity to PCC in aMCI group compared to healthy elderly group. Conclusion: Impaired functional connectivity between PCC and a distributed set of brain areas are considered as the biological basis of hypo-activity in episodic memory in aMCI patients. Increased PCC functional connectivity may be indicative of functional compensation.