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Longitudinal brain activity changes in asymptomatic Alzheimer disease.
Brain and Behavior
|June 29, 2012
Summary
Individuals with asymptomatic Alzheimer disease (ASYMAD) show unique early brain blood flow changes, suggesting resilience factors. These findings reveal early functional alterations that may help maintain normal cognition despite Alzheimer pathology.
Area of Science:
- Neuroscience
- Neuropathology
- Medical Imaging
Background:
- Asymptomatic Alzheimer disease (ASYMAD) presents normal cognition with significant Alzheimer disease (AD) pathology.
- Cognitive resilience factors in ASYMAD remain incompletely understood.
- Early changes in regional cerebral blood flow (rCBF) may indicate resilience mechanisms.
Purpose of the Study:
- To identify factors contributing to cognitive resilience in ASYMAD.
- To compare early longitudinal rCBF changes in ASYMAD with cognitively normal (CN) and cognitively impaired (CI) individuals.
- To correlate neuropathological findings with observed rCBF alterations.
Main Methods:
- Longitudinal positron emission tomography (PET) rCBF measurements were obtained from cognitively intact participants up to 10 years before death.
- Participants were categorized into CN, ASYMAD, and CI groups based on clinical and autopsy data.
- Voxel-based analysis compared longitudinal rCBF changes and correlated them with CERAD, Braak scores, and quantitative measures of tau and amyloid.
Main Results:
- ASYMAD and CI groups exhibited similar AD pathology (CERAD, Braak scores, amyloid, tau) compared to CN.
- Both ASYMAD and CI groups showed longitudinal rCBF declines in precuneus, lingual, and middle temporal gyrus (MTG) regions relative to CN.
- CI group had greater rCBF decreases in cingulate, cuneus, and brainstem regions; ASYMAD showed relative rCBF increases in medial temporal and thalamic regions compared to CI and CN.
Conclusions:
- ASYMAD individuals demonstrate distinct patterns of early regional cerebral blood flow alterations.
- These early functional changes, particularly in medial temporal and thalamic regions, may represent a compensatory mechanism contributing to cognitive resilience.
- Findings suggest that early alterations in brain hemodynamics play a role in maintaining cognitive function despite underlying Alzheimer pathology.
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