A conserved EEG deformation?
Two independently sourced case–control cohorts representing distinct positions in a hypothesized disease process move in the same direction under a shared EEG observable. The directional correspondence recurs across independently acquired cohorts. The stronger claim—that both observations lie on one disease-progressive coordinate—is not established.
The signal survives replication. The interpretation does not get a free pass.
The shared observable is q = log(σ12–16 Hz / α8–12 Hz), evaluated through the same deformation-estimation pipeline in two independently acquired case–control EEG cohorts.
The cohort-specific disease displacements are compared as vectors under a common representation; cos θ reports their directional alignment, while the orthogonal residual reports the component of one deformation not captured by the shared direction.
What turns concordance into a disease-process coordinate?
What statistical structure would justify treating these two concordant disease-associated deformations as observations of one latent progressive coordinate rather than two related but phenotype-specific contrasts?
A stronger claim would require prespecified stability across resampling, measurement choices, and independent data, together with temporal or predictive information beyond the cross-sectional contrasts used to define the shared direction.
What evidence would justify the stronger claim?
The next step is not another favorable correlation. It is a prespecified test of whether the shared component remains stable across independent data and carries information not used to define it.
Until that evidence exists, the result remains a reproducible cross-cohort correspondence rather than a disease-progression coordinate.
Inference boundary. These analyses are cross-sectional and cohort-comparative. They do not establish longitudinal transition between the cohorts, causality, or a unique latent disease trajectory.