Geng Report: Concerns regarding unusually low variance in spPSP frequency data and inability to assess image integrity in "Functional recovery of the adult murine hippocampus after cryopreservation by vitrification" (PNAS, 2026)

Academic fraud report · Geng Detector

Summary

This report evaluates the PNAS article by German et al. (DOI: 10.1073/pnas.2516848123) concerning functional recovery of the murine hippocampus after vitrification. The overall verdict is "Suspicious / Inconclusive" (yellow flag). The principal concern is Finding 1: the authors report spontaneous postsynaptic potential (spPSP) frequency as 1.14 ± 0.014 Hz (n = 12 from 6 mice), yielding an implausibly low coefficient of variation (~1.2%) for electrophysiological recordings, which are typically subject to substantial biological and technical noise. Finding 2 is treated as a mitigating green flag: authors candidly disclose a 1-out-of-3 success rate for in situ whole-brain vitrification, arguing against systematic fabrication. Finding 3 confirms timeline and reagent plausibility (submitted June 26, 2025; accepted January 18, 2026). Finding 4 notes insufficient pixel-level data to assess potential image manipulation. No definitive fraud finding is made; result is based on textual evidence only.

Verdict

Suspicious / Inconclusive (Yellow Flag). One substantive statistical concern (implausibly low variance in spPSP frequency) is identified, partially offset by unusually candid reporting of a 33% experimental success rate. Image-based integrity checks could not be performed. Final determination requires raw data inspection and institutional investigation.

Key findings

Implausibly low variance in spPSP frequency data — reported as 1.14 ± 0.014 Hz (n = 12 from 6 mice), giving a coefficient of variation of ~1.2%, which is biologically atypical for slice electrophysiology and suggestive of overfitting, cherry-picking, or post-hoc smoothing.
Candid reporting of low experimental success rate (green flag) — authors explicitly state that only 1 out of 3 iterations of the in situ vitrification protocol yielded slices suitable for physiological evaluation; the remainder were excluded due to inadequate perfusion or absent electrophysiological activity.
Timeline and materials are internally consistent — paper received June 26, 2025; accepted January 18, 2026; reagents (V3, VM3) and instruments (Seahorse XFe96) are consistent with current availability.
Image-based forensics undetermined — no pixel-level access to Figures 1–4, so Western blot splicing, image rotation, duplication, or background manipulation could not be assessed.

Evidence highlights

Page 7, Results section ("Cerebral Vitrification In Situ"): "…manifested in spontaneously occurring postsynaptic potentials (spPSPs, 1.14 ± 0.014 Hz, n = 12 from 6 mice; Fig. 4D)."
Page 6, Results section: "One out of three iterations of the final protocol of interleaved equilibration, vitrification, and hyperoncotic washout yielded brain slices suitable for physiological evaluation… The remaining iterations had to be excluded from the analysis due to either inadequate perfusion quality or absence of detectable electrophysiological activity."
Page 1 (journal header): "received June 26, 2025; accepted January 18, 2026."
DOI: 10.1073/pnas.2516848123
Citation: German A, Akdaş EY, Flügel-Koch C, et al. Functional recovery of the adult murine hippocampus after cryopreservation by vitrification. *PNAS* 123(10), 2026.

Notes

The SD value of 0.014 is transcribed exactly as printed in the report; verify against the published PDF for any typographical corrections.
Confidence in Finding 1 is moderate: the value is anomalous on its face but a single statistic alone cannot prove misconduct; alternative explanations (e.g., software filtering, sample selection criteria) must be excluded.
Finding 2 is not scored as an irregularity; it functions as a mitigating indicator against systematic fabrication.
Pixel-level image analysis (Fiji/ImageJ forensic plugins, similarity hashing) was not possible with the materials provided.
Recommended follow-up: request raw spPSP event timestamps and per-cell scatter plots from the corresponding author; perform re-analysis of variance; if unresolved, escalate via PubPeer comment or institutional review.