Abstract W P368: Longitudinal Change in fMRI Blood Oxygen Level Dependent Signal in Cerebral Amyloid Angiopathy
Bibliographic record
Abstract
Introduction: Previous cross-sectional studies show that cerebral amyloid angiopathy (CAA) is associated with reduced blood oxygen level dependent (BOLD) signal change in response to a visual task, and that this reduction is due to impaired vascular reactivity. However, there are no data on the rate at which the BOLD signal changes over time in CAA. We hypothesized that fMRI activation would decline in CAA, representing progressively impaired vasoreactivity, and this decline would be associated with increased white matter hyperintensity (WMH) volume. Methods: fMRI BOLD amplitude was measured in response to a visual task (alternating checkerboard pattern) at study entry and 1-year follow-up for 18 patients with probable CAA by Boston criteria, and 15 healthy controls. fMRI data were matched to a canonical BOLD signal using a general linear model resulting in z-statistic images with a significance threshold of p<0.05 using FSL. The amplitude of the BOLD signal percent change from baseline was measured in the 200 most active voxels in the primary visual cortex. WMH were identified on fluid attenuated inversion recovery (FLAIR) images and the volume was measured using Quantomo software (Cybertrials Inc, Canada). Results: BOLD amplitude was lower at follow-up than baseline in CAA, but the difference was not significant (mean change -0.14±0.55, p=0.30). Mean BOLD amplitude was similar at baseline and follow-up in controls (mean change 0.20±0.49, p=0.14). The difference in rate of change over time between CAA and controls was borderline significant (p=0.04). fMRI was lower at follow-up than baseline in 11/18 CAA compared to 4/15 controls (p=0.08). In CAA patients, WMH increased over time (median 1.44 mL interquartile range -0.22 to 9.70mL, p=0.01). However, BOLD amplitude change and WMH change were not related (r=-0.01, p=0.96). Discussion: Although we did not see significant fMRI BOLD signal reduction from baseline to 1 year in CAA, we did see a difference in change over time between CAA and controls, consistent with our hypothesis that impaired vasoreactivity is a feature of CAA. Studies with larger numbers of patients, or longer duration of follow-up, are needed to more precisely determine the rate of change over time in reduction of fMRI BOLD amplitude in CAA.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".