Amyloid and tau PET demonstrate region-specific associations in normal older people

(beta-amyloid (A beta) and tau pathology become increasingly prevalent with age, however, the spatial relationship between the two pathologies remains unknown. We examined local (same region) and non-local (different region) associations between these 2 aggregated proteins in 46 normal older adults using [F-18]AV-1451 (for tau) and [C-11]PiB (for A beta) positron emission tomography (PET) and 1.5 T magnetic resonance imaging (MRI) images. While local voxelwise analyses showed associations between PiB and AV-1451 tracer largely in the temporal lobes, k-means clustering revealed that some of these associations were driven by regions with low tracer retention. We followed this up with a whole-brain region-by-region (local and non-local) partial correlational analysis. We calculated each participant's mean AV-1451 and PiB uptake values within 87 regions of interest (ROI). Pairwise ROI analysis demonstrated many positive PiB AV-1451 associations. Importantly, strong positive partial correlations (controlling for age, sex, and global gray matter fraction, p <.01) were identified between PiB in multiple regions of association cortex and AV-1451 in temporal cortical ROIs. There were also less frequent and weaker positive associations of regional PiB with frontoparietal AV-1451 uptake. Particularly in temporal lobe ROIs, AV-1451 uptake was strongly predicted by NB across multiple ROI locations. These data indicate that A beta and tau pathology show significant local and non-local regional associations among cognitively normal elderly, with increased PiB uptake throughout the cortex correlating with increased temporal lobe AV-1451 uptake. The spatial relationship between A beta and tau accumulation does not appear to be specific to A beta location, suggesting a regional vulnerability of temporal brain regions to tau accumulation regardless of where AP accumulates.