Posterior 7–13 Hz alpha frequency had a negative age slope under ±1 exponent changes in fixed spectra from 108 ds003775 participants

We tested how changes in a fitted spectral background can change an alpha frequency age slope. We used fixed posterior spectra from 108 first visits in OpenNeuro ds003775 version 1.2.1. An upper envelope of log power lines gave the possible 7–13 Hz maxima. Fixed ordinary least squares weights gave sharp coefficient bounds under independent exponent intervals. With sex adjustment and exponent changes up to ±1, all allowed age slopes were negative. The bounds were -0.02416682 to -0.00953911 Hz per year. All five planned checks also retained a negative slope at radius 1. The first possible primary reversal required a radius strictly above 2.0158135109. A saved reversal witness used 62 negative exponents. The radius is a sensitivity choice, not an estimate of fitting error or a confidence interval. The package preserves the proof, NumPy tool, 153 spectrum files, metadata, pinned source identities, results, witnesses, and reproduction instructions. Independent calculations checked every bound. One fresh raw EEG replay matched all six stored arrays exactly. All nine analysis outputs matched a separate offline rebuild.

EEG · alpha frequency · age · spectral background · sensitivity analysis · upper envelope · ordinary least squares · OpenNeuro ds003775