Greater Amyloid Burden in Cognitive Networks in Preclinical Alzheimer's Disease
Background:
In preclinical Alzheimer's disease (pAD), regional patterns of amyloid-β (Aβ) deposition are well characterized but it is unclear how this process varies across functional networks.
Objective:
Determine how Aβ accumulation in functional networks ("network-amyloid burden" [NAB]) varies by age, network type (cognitive vs. non-cognitive), and Aβ status (Aβ+/Aβ-), and relates to cognition.
Methods:
157 cognitively unimpaired adults (45-84 years; n=28 Aβ+ per neuroradiological read) underwent brain MRI, amyloid PET (18F-florbetapir), and neuropsychological testing. NAB was calculated as the mean standard uptake value ratio within 7 networks categorized as cognitive (fronto-parietal, default mode, ventral and dorsal attention, limbic) or non-cognitive (somato-motor, visual). Linear mixed models tested how NAB varies across age, networks (by type and each separately), Aβ status, and their interactions, and relationships between NAB and cognition.
Results:
NAB increased with age, most prominently in fronto-parietal and default mode networks. NAB was higher in cognitive than non-cognitive networks, and this difference was more pronounced in Aβ+ individuals. NAB was not significantly associated with cognition.
Conclusions:
Cognitive brain networks are more vulnerable to amyloid accumulation with aging and in pAD than non-cognitive networks. Cognitive NAB may be useful for early detection and as a target for intervention in pAD.
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