Average reference increases alpha edge counts below minus 0.5 in 88 ds004504 v1.0.9 records at normalized ridge 0.001

We tested ridge partial correlation after common average reference in 88 processed EEG records from OpenNeuro ds004504 v1.0.9. Each record had 19 channels. Alpha was 8 to less than 13 Hz. The ridge variance was 0.001 times the mean channel variance under each reference. The median fraction of 171 edges below minus 0.5 was 60.8% after average reference and 5.3% under the supplied reference. The fraction increased in all 88 records. A matched absolute ridge check gave the same direction in all records. The proof shows that every ridge partial correlation approaches minus one if average reference imposes the only null direction. Additional null directions change that limit. Fifty-two records had numerical rank below 18, so the package retains their full spectra. A sufficient finite bound confirmed all edges at or below minus 0.5 in two primary records. The package includes a checked audit tool, complete source band matrices, proofs, results, source hashes, metadata, licenses, and reproduction commands. Separate regression calculations checked 15,048 primary edges. Two fresh source extractions and a second offline run reproduced the saved values. The result describes these covariance models. It does not show neural inhibition or establish true neural connectivity.

EEG · average reference · ridge regularization · partial correlation · covariance · singular covariance · null space · numerical rank · signal processing