Neurodegeneration
Mapping amyloid plaques and brain connectivity in Alzheimer's
Open access · cc by · source: Europe PMC
Amyloid-beta plaques accumulate within highly connected brain hubs, but locally, this accumulation actively disrupts and reduces that very connectivity.
How this study connects
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Pathological states like Alzheimer's disease severely disrupt DMN connectivity, which is driven by local neuroinflammation and the local destructive effects of amyloid-beta accumulation.
Evidence for the claim as stated.
Study at a glance
- Design
- Case-control — Amyloid PET and intrinsic network connectivity in prodromal AD vs controls
- N
- N=35 · 23 patients and 12 controls after excluding corrupted PET (from 24 and 16 recruited)
- Population
- Patients with prodromal Alzheimer's disease and healthy controls
- Outcome
- Within-patient correspondence of amyloid deposition and intrinsic network connectivity
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Mapping amyloid plaques and brain connectivity in Alzheimer's
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
23 patients in final analysis
One patient and four control participants were excluded from further analysis because of corrupted PET data, resulting in all analyses being conducted on 23 patients and 12 healthy control participants.
1.15 neocortical standardized uptake value ratio cutoff
We used a cut-off for ‘high’ or ‘low’ neocortical standardized uptake value ratios of 1.15, consistent with cut-off values used in previous PiB-PET studies ().
Key findings
The study revealed that amyloid-beta plaques preferentially accumulate in high-connectivity fronto-parietal and default mode network cores. However, once this baseline positive correlation was statistically removed, local searchlight analysis showed a strong negative correlation, meaning that local plaque accumulation directly reduced functional connectivity. This localized disruptive effect was highly visible across several attention networks, not just the default mode network.
Methodology
Researchers investigated the relationship between amyloid-beta buildup and brain wiring in 23 patients with early-stage Alzheimer's disease and 12 healthy controls. They used PET scans with a specialized tracer to measure plaque density and resting-state fMRI to record functional connectivity. By applying a novel within-patient statistical approach, they separated the global pattern of plaque buildup from its local effects on neural networks.
Limitations
Because the study utilized a cross-sectional design, it cannot prove that plaque accumulation causes the decline in connectivity over time. Additionally, the small sample size of 23 patients and 12 controls limits how well these findings generalize to larger populations. Finally, the study focused strictly on patients in the prodromal phase of Alzheimer's, meaning these network dynamics may shift as patients progress to severe dementia.
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