Wavelet Phase Synchronization Analysis of Cerebral Blood Flow Autoregulation
Bibliographic record
Abstract
The dynamic relationship between beat-to-beat mean arterial blood pressure (ABP) fluctuations and cerebral blood flow velocity (CBFV) variations have been intensively studied. The experimentally observed low coherence in the low-frequency band has previously indicated that the assumptions of linearity and/or stationarity, the preconditions of the linear transfer function analysis, are not valid in that frequency region. Latka et al. [M. Latka, M. Turalska, M. Glaubic-Latka, W. Kolodziej, D. Latka, and B. J. J. West, "Phase dynamics in cerebral autoregulation," Amer. J. Physiol. Heart Circ. Physiol., vol. 289 pp. H2272-H2279, Jul. 2005] used a wavelet phase synchronization method to identify the instantaneous phase difference between ABP and CBFV, and low values of synchronization index were found in the low-frequency range, seeming to provide further evidence that the cerebral autoregulation system is nonstationary. Here, we focus on another possible factor corresponding for this low synchronization index-unmeasured variability. We demonstrate analytically and with a physiologically based cerebral hemodynamic model that, in the case of multiple inputs, the phase difference between one input, ABP, and the output, CBFV, will be distorted by an additional input, end-tidal CO(2) (P(ETCO(2))), and no longer accurately represent the true ABP-CBFV system phase shift. We also prove that this phase distortion can be corrected if the transfer functions for ABP-CBFV and P(ETCO(2))-CBFV are known or can be estimated. A significantly increased value of synchronization index in the low-frequency band is found by using the CO(2) correction term with experimental data on 13 subjects. This essentially indicates that the lack of synchronization between ABP and CBFV previously identified by Latka et al. [M. Latka, M. Turalska, M. Glaubic-Latka, W. Kolodziej, D. Latka, and B. J. J. West, "Phase dynamics in cerebral autoregulation," Amer. J. Physiol. Heart Circ. Physiol., vol. 289, pp. H2272-H2279, Jul. 2005] can be partly attributed to unmeasured variability.
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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 | 0.001 | 0.001 |
| 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".