Kennedy KM, Rodrigue KM, Hebrank AC, Devous Sr MD, Park DC.
Precuneus beta-amyloid burden is associated with decreased bilateral frontal activation and default network suppression in healthy adults.
Human Amyloid Imaging 2011 Meeting Abstracts. 2011 Jan 15;
Limited evidence suggests that increased beta-amyloid deposition even in apparently healthy adults is associated
with alterations in functional activity. However, the majority of these findings report on resting-state activity or
functional connectivity. Less well understood are the effects of increased beta-amyloid burden on patterns of
task-relevant activations. The goal of the current study was to investigate the modifying effects of regional amyloid
burden on BOLD-signal activation during the viewing of scenes in a subsequent memory task within a continuous
age sample of healthy adults (N = 137; 30-89 years old). Participants underwent PET scanning using 18F-AV-45
and a separate fMRI scanning session. Amyloid burden was obtained from the precuneus, a region that shows
increasing amyloid load with age. The fMRI task consisted of presentation of 96 outdoor landscape scenes and
participants indicated whether or not there was water present in the scene. Out of the scanner, participants were
later presented with the same 96 scenes interspersed with 96 matched lures. Encoding trials were backsorted by
whether they were remembered with high or low confidence or forgotten. Using SPM, we conducted general linear
model analyses on individual-level encoding contrasts with age and precuneus uptake as continuous predictors.
We found that during viewing of scenes that were subsequently remembered with high confidence, those individuals
with greater precuneus amyloid burden evidenced less activation in bilateral dorsolateral prefrontal cortex and
decreased suppression in bilateral lateral temporal and medial frontal cortex regions. Thus increasing amyloid
burden exerts negative effects on brain function in both task-active regions routinely recruited as compensatory
mechanisms during tasks that pose higher cognitive demands, and in regions comprising the default network.
Supported in part by NIH grants 5R37AG-006265-25, 3R37AG-006265-25S1, and Alzheimer's Association grant
IIRG-09-135087. Radiotracer was generously provided to the study by Avid Radiopharmaceuticals.