Directional sensitivity of the cerebral pressure-flow relationship in middle and posterior cerebral arteries using the repeated squat-stand model: within-day reproducibility and impact of diurnal variation in young healthy men and women
Bibliographic record
Abstract
Abstract We recently employed repeated squat-stands (RSS) to quantify directional sensitivity of the cerebral-pressure flow relationship (i.e. hysteresis) using a novel metric. Within-day reproducibility and diurnal variation impacts of this metric are unknown. We evaluated this metric for: 1) within-day reproducibility and the extent diurnal variation has in middle (MCA; ΔMCAv T /ΔMAP T ) and posterior cerebral arteries (PCA; ΔPCAv T /ΔMAP T ); 2) sex differences. Absolute (ΔMCAv T /ΔMAP T ; ΔPCAv T /ΔMAP T ) and relative (%MCAv T /%MAP T , %PCAv T /%MAP T ) metrics were calculated at seven time-points (08:00-17:00) in 18 participants (8 women; 24 ± 3 yrs) using the minimum-to-maximum MCAv/PCAv and MAP for each RSS at 0.05 Hz and 0.10 Hz. Reproducibility was evaluated with intraclass correlation coefficient (ICC). For all metrics, reproducibility was good (0.75-0.90) to excellent (>0.90). The metric in both arteries was impacted by MAP direction at 0.10 Hz (all p < 0.024). Time-of-day influenced ΔMCAv T /ΔMAP T (0.05 Hz: p = 0.0028; 0.10 Hz: p = 0.0009), %MCAv T /%MAP T (0.05 Hz: p = 0.035; 0.10 Hz: p = 0.0087), and ΔPCAv T /ΔMAP T (0.05 Hz: p = 0.0236). Sex differences in the MCA (p = 0.0028) vanished in relative terms and was absent in the PCA. These findings demonstrate within-day reproducibility of this metric in both arteries. Moreover, hysteresis is not impacted by sex.
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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 | 0.002 | 0.005 |
| 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) | 0.001 | 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".