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P4‐188: Longitudinal increases in PiB are associated with temporal lobe cortical volume loss in asymptomatic participants
Author(s) -
Benzinger Tammie,
D'Angelo Gina,
Blazey Tyler,
Zhou Gongfu,
Ances Beau,
Vlassenko Andrei,
Morris John
Publication year - 2012
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2012.05.1892
Subject(s) - pittsburgh compound b , temporal lobe , positron emission tomography , atrophy , nuclear medicine , medicine , white matter , psychology , magnetic resonance imaging , alzheimer's disease , neuroscience , disease , radiology , epilepsy
lated global gray matter (GM) volumes, white matter hyperintensity (WMH) volumes, and fractional anisotropy (FA norm, a measure of white matter integrity) from T1 V weighted, FLAIR, and diffusion tensor MRI. fMRI image preprocessing and FC analyses identified a set of functionally inter-correlated regions traditionally referred to as the default mode network (DMN): posterior cingulate (PCC), medial prefrontal (MPF), and right and left inferior parietal (RIP, LIP) cortices. FC values for 6 pairwise connections among these regions were calculated and Z transformed. To explore the magnitude of connectivity reductions with age, we normalized each elderly FC (FC norm) by dividing by corresponding average young FC. We then used principal components analysis (PCA) to analyze patterns of covariance among the pairwise connectivity reduction values among elders. Results: FC among distinct node pairs was heterogeneous in the young, but was substantially reduced in all 6 connections among elders (Table; all P’s<0.001), with MPF-PCC connections showing the greatest reduction (43% of young mean on average). PCA suggested that the set of 6 pairwise connectivities was well explained by a single principal component representing global, coordinated reductions to all 6 connections. Within elders, associations between FC norm and age, GM, and WMH were not significant; however greater global FA norm was associated with lesser MPFPCC (P 1⁄4 0.009) and MPF-RIP (P 1⁄4 0.04) FC norm. Conclusions: In healthy aging, functional connectivity among all pairs of DMN nodes may reduce in a coordinated fashion from heterogeneous peak young adult values. These connectivity reductions do not co-occur with brain structural changes in a straightforward or linear way. It is critical to understand the biological basis of age-related network connectivity reductions, which may reflect diverse biological processes of brain aging.