Relationship between Amyloid-ß Deposition and the Coupling between Structural and Functional Brain Networks in Patients with Mild Cognitive Impairment and Alzheimer's Disease.

Previous studies have demonstrated that the accumulation of amyloid-ß (Aß) pathologies has distinctive stage-specific effects on the structural and functional brain networks along the Alzheimer's disease (AD) continuum. A more comprehensive account of both types of brain network may provide a better characterization of the stage-specific effects of Aß pathologies. A potential candidate for this joint characterization is the coupling between the structural and functional brain networks (SC-FC coupling). We therefore investigated the effect of Aß accumulation on global SC-FC coupling in patients with mild cognitive impairment (MCI), AD, and healthy controls. Patients with MCI were dichotomized according to their level of Aß pathology seen in 18F-flutemetamol PET-CT scans-namely, Aß-negative and Aß-positive. Our results show that there was no difference in global SC-FC coupling between different cohorts. During the prodromal AD stage, there was a significant negative correlation between the level of Aß pathology and the global SC-FC coupling of MCI patients with positive Aß, but no significant correlation for MCI patients with negative Aß. During the AD dementia stage, the correlation between Aß pathology and global SC-FC coupling in patients with AD was positive. Our results suggest that Aß pathology has distinctive stage-specific effects on global coupling between the structural and functional brain networks along the AD continuum.