Disrupted Functional Connectivity Related to Differential Degeneration of the Cingulum Bundle in Mild Cognitive Impairment Patients

Previous studies have demonstrated that Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) exhibited anatomical and functional abnormalities in the anterior cingulate cortex (ACC) and accumulating evidence supported the hypothesis that changes in the ACC predict the progression from aMCI to AD. In this study, we aimed to explore how the two functional and structural heterogeneous sub-regions of ACC, namely the dorsal ACC (dACC) and the ventral ACC (vACC), changed in aMCI and whether the structural connectivity affects the functional connectivity between the two ACC subregions. To investigate this hypothesis, we studied resting-state fMRI and DTI images in a group of 24 aMCIs and 29 healthy controls. The dACC exhibited a significantly increased functional connectivity in the Salience Network (SN) and a decreased functional connectivity with the vACC in aMCI. The DTI results showed that the bilateral cingulum fibers were the most damaged tracts in aMCI and that the fractional anisotrophy of the left anterior cingulum was significantly correlated with the functional connectivity between the two ACC sub-regions. In conclusion, this study revealed the pathological changes in the intrinsic functional connectivity of the ACC within SN, as well as the connectivity between the dACC and vACC in aMCI. Our study also revealed that disrupted white matter integrity of the anterior regions of the cingulum was associated with the alterations in subregional connectivity in the ACC.