Debiased reproducible dimensionality is lower under isoflurane than in wakefulness in the same mouse brain, at matched trial counts and stimulation currents

Perturbational complexity distinguishes conscious from unconscious brain states, but companion work by this author showed that the standard estimator (PCIst) partly reflects a selection bias, and that what it tracks is the response's reproducible dimensionality (R-dim), estimated fully out-of-sample. This preprint takes the debiased estimator to the within-subject arousal-state contrast it was built for, using the open Allen Institute dataset of cortical electrical stimulation with epidural EEG in head-fixed mice, each animal recorded awake and under isoflurane (DANDI 000458). All hypotheses, exclusions, matching rules and a four-cell interpretation matrix were preregistered with public timestamps before any neural signal was read. Because R-dim grows with trial count, all state comparisons were made at matched trial counts and matched stimulation currents within each animal - to the author's knowledge the first arousal-state comparison of perturbational complexity controlling for both. Results: R-dim was lower under isoflurane than awake (medians 2.08 vs 2.80 at 120 matched trials; 16/20 animals; p = 0.008), robust across all four preregistered sensitivity analyses - and the effect strengthened when the response window was moved further from the stimulation artifact, arguing against artifact leakage. The growth curves of the two states ran in parallel across 30-480 trials: anesthesia lowered the level of reproducible dimensionality without detectably changing its growth with trials. Two preregistered predictions failed and are reported in full. Curve flattening under anesthesia was not detected, but that test was underpowered (39% for a moderate effect), so the question remains open. Recovery did not restore R-dim in a test that was adequately powered (90%); by the sealed interpretation matrix, the headline claim is therefore downgraded from "tracks the state" to "is associated with the state, with temporal drift not excluded". Finally, on identical matched trials, standard PCIst separated the states by a larger relative margin (+32% vs +22%) yet did not reach significance across animals (p = 0.19), while debiased R-dim did (p = 0.008): the bias-corrected estimator detects the arousal-state contrast more consistently than the estimator the field currently uses. Files: full preprint (HTML), two figures, and a reproducible code archive with all analysis scripts, sealed preregistrations, per-animal results, and the mechanical verifier that recomputes every number claimed in the paper. No raw neural data are redistributed.