Increased functional connectivity of anterior insula to anterior cingulate cortex in amnestic mild cognitive impairment: A longitudinal resting‐state fMRI study

Abstract

AbstractBackgroundThe insula has been reported as a crucial role in Alzheimer’s disease (AD) and amnestic mild cognitive impairment (aMCI). However, the mechanism and functional connectivity (FC) changes of insula in follow‐up remain unclear. Exploring specific insula network interaction can contribute to a better understanding of integration and segregation patterns of aMCI.MethodTwenty aMCI and twenty healthy controls (HC) participants were recruited and underwent resting‐state functional magnetic resonance imaging (rs‐fMRI) and neuropsychological assessment at baseline and 15 months afterward. Rs‐fMRI data were preprocessed using SPM 12 and CONN software. FC of two insular subregions in each hemisphere were defined as anterior insula connectivity (AIC) and posterior insula connectivity (PIC). Using data driven clustering technique, the insular lobe was subdivided based on whole brain functional connectivity. Two‐way analysis of covariance was used with covariates of gender, age, education, follow‐up interval, volume of gray matter and global correlation (GCOR).ResultWithin group FC maps of HC and aMCI exhibited similar patterns both at baseline and follow‐up. For the left anterior insula, significant connectivity with bilateral anterior cingulate gyrus (ACC), paracingulate gyrus, putamen, frontal orbital cortex, inferior frontal gyrus, and temporal pole were identified. The right anterior insula was positively associated with bilateral insula, ACC, central opercular cortex, frontal orbital cortex, and right junction region of temporal, frontal and parietal lobe. The posterior zone of the insula (both the right and the left) exhibited significant connectivity with the bilateral Insular, ACC, central opercular cortex, precentral gyrus, postcentral gyrus, supramarginal gyrus, parietal operculum cortex, as well as the junction region of temporal, frontal and parietal lobe. For interactive main effects, the right AIC showed significantly increased FC with the left ACC, while the left PIC showed decreased FC with the right precuneous, in aMCI as compared to HC.ConclusionInsula rsFC changes could be potential biomarkers of aMCI and reveal some definite neuropathological mechanism due to pathologic processes in AD. We considered the rsFC increase of AIC with ACC as compensatory and decrease of the PIC with the precuneus as deterioration of follow‐up due to the course of disease.