PATTERNS OF INCREASED AND DECREASED PRECUNEUS FUNCTIONAL CONNECTIVITY IN SCD DEPENDING ON AMYLOID STATUS

The precuneus/posterior cingulate (PCC) is a hub region of the default-mode network (DMN) and a prominent target of amyloid-beta (Aß) deposition in MCI and AD causing subsequent disruptions of DMN functional connectivity (FC). In subjective cognitive decline (SCD), amyloid load effects on posterior DMN FC are less well known. We aimed to compare precuneus FC in SCD with and without amyloid deposition and to disentangle the contributions of regional & global Aß load. We included age and sex-matched 24 SCDAß+ and 22 SCDAß- individuals from the DELCODE-PET sub-cohort (Tab. 1), based on qualitative ratings of [18F]florbetaben (Neuraceq™) PET scans by two experienced readers. Global and regional amyloid burden was quantified by standard uptake value ratios (SUVR) using cerebellar cortex as reference region. Resting-state fMRI data were acquired at 3T, and preprocessed and analyzed with DPARSFA. Seed-based FC maps were generated between the time series of a bilateral precuneus seed region and each voxel of the whole brain, respectively. Voxelwise FC group differences in two-sample t-tests were considered significant at p < 0.005 voxel-level and p < 0.05 FWE cluster-level. For clusters showing significant group differences, follow-up analyses explored correlations between their mean FC values and (i) regional PCC amyloid load and (ii) global amyloid load. Precuneus FC was significantly increased with occipital and lingual/cerebellar regions, and significantly decreased with left superior/middle frontal and left inferior parietal / angular regions in SCDAß+ as compared to SCDAß (Tab.2, Fig.1). In the SCDAß+ group only, precuneus-occipital mean FC showed a significant positive correlation with PCC amyloid load (r=0.42, p=0.04) (Fig.2).