Comparison of neuronal activity profiles in Alzheimer’s disease and frontotemporal dementia measured by resting‐state fMRI
Bibliographic record
Abstract
Abstract Background Neuronal activity (NA) and metabolism are impaired in the early stages of Alzheimer’s Disease (AD) and Frontotemporal Dementia (FTD) leading to specific patterns of cognitive decline. Detailed disease models elucidating how and where in brain these NA disturbances commence and how they gradually progress remain incomplete. Recently, we introduced several NA metrics quantified based on fluctuations of the resting‐state fMRI (rs‐fMRI) signal. NA was significantly lower in AD and mild cognitive impairment compared to normal elderly controls (NEC). Here we extend this work using the most sensitive metric to examine NA profile differences between people with AD and FTD. Method 3T MRI rs‐fMRI data (TR=∼2.4 Sec, 250 volumes) were obtained from the Ontario Neurodegenerative Disease Research Initiative (AD group: N=40, aged 71.8 ± 8.1, 42% female; and FTD group: N=50, aged 67.8 ± 7.3, 36% female), and Gait and Brain Study (NEC group: N=46, aged 71.0 ± 5.5, 33% female). The rs‐fMRI signal was pre‐processed and decomposed into independent components (ICs) using IC analysis. The ICs were classified into neuronal and non‐neuronal sources using a support vector machine classifier. Voxelwise NA was quantified based on the magnitude of neuronal ICs in the rs‐fMRI signal composition. This metric was utilized to create resting‐state NA maps in each subject, which were compared between groups voxel by voxel using a multiple comparisons permutation test (MCPT) with 1000 permutations. Result Group average NA maps are provided in Fig. 1. Average NA was lower in FTD (24%) and AD (40%) compared to NEC. There was a significant difference (adjusted p‐values from MCPT) between NEC and FTD (p<0.001), NEC and AD (p<0.001), and FTD and AD (p<0.05). Difference NA maps comparing the groups and associated significance maps are shown in Fig. 2. The FTD group had significantly higher NA compared to AD in ∼53% of brain voxels (Fig. 2). Conclusion Significantly lower NA was detected in AD and FTD compared to NEC. Localized significant NA differences between AD and FTD were detected emerging mostly as clusters in occipital and subcortical areas that are known to be less affected by FTD.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.000 | 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".