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Beyond Emotional and Spatial Processes: Cognitive Dysfunction in a Depressive Phenotype Produced by Long Photoperiod Exposure · 10.1371/journal.pone.0170032

Name: Verified Rigor Record — Beyond Emotional and Spatial Processes: Cognitive Dysfunction in a Depressive Phenotype Produced by Long Photoperiod Exposure · 10.1371/journal.pone.0170032
Item: Beyond Emotional and Spatial Processes: Cognitive Dysfunction in a Depressive Phenotype Produced by Long Photoperiod Exposure · 10.1371/journal.pone.0170032
Rating: 71
Author: Αlpha¹

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Αlpha¹ Editorial

This rigor review was examined and confirmed by Αlpha¹ Editorial · July 6, 2026

Αlpha¹ Rigor Review

Rigor Reviewed

WARN

Warnings to address · Interventional Study

Eight dimensions — click a segment for details

Critical

High-priority

Model-reported confidence: highReviewer agreement: moderateEngine: 7.6.0Source: full text

Not verified in this report

No data or code availability links were detected to verify.

This Αlpha¹ Rigor Review uses AI Rigor Reviewers trained on a curated corpus of high-fidelity and retracted papers, with expert supervision and curation. It can still make mistakes; verify each finding against the source before relying on it.

The paper has a strong scientific premise and ethical approvals, but suffers from major gaps in study design (no randomization, power analysis, or blinding details), data/code availability (none reported), and key resource identification (rat source missing). Statistical reporting is adequate but lacks effect sizes and assumption checks, and reporting transparency is marred by a missing COI statement and reporting guideline.

All eight dimensions were applicable and evaluated. The reviewers largely converged on the major issues, with minor divergence on the severity of key resources and reporting transparency gaps. The statistics verification component checked 19 tests and found all consistent, but this does not validate the entire analysis.

12 major claims checked against the paper's own evidence: all adequately supported.

Recomputed 19 tests: 19 consistent, 0 inconsistent, 19 via agent-written checks.

3 integrity concerns flagged (0 high).

Rigor

Eight Dimensions3 pass · 3 warn · 2 fail

12 major claims3 partial9 supported

The introduction provides a thorough background on depression, cognitive deficits, and the rationale for using the novel object recognition task. It explicitly acknowledges limitations of prior studies, such as reliance on spatial memory tasks and confounding emotional factors, and explains how the present model addresses these issues.

Sub-criteria

prior work citedADEQUATE

premise rationaleADEQUATE

limitations addressedADEQUATE

Per reviewer (3) — the votes behind the verdict

PASSReviewer 1· 95% conf

The paper clearly establishes the scientific foundation for studying cognitive deficits in depression using a long photoperiod model, citing relevant prior work and addressing limitations of previous approaches.

Evidence

direct quote[Introduction, paragraphs 1–3]

“There are cognitive dysfunctions also present in depression, which have been shown to persist even when the affective symptoms are in remission, and worsen with every depressive episode”

direct quote[Introduction, paragraph 6]

“The NOR task is well-suited for studying depression-related cognition, because it does not employ any emotional responses, thus providing a relatively clear measure of memory and cognition.”

direct quote[Introduction, paragraph 5]

PASSReviewer 2· 90% conf

The paper establishes a clear scientific premise by citing prior work on depression-related cognitive deficits, the role of sleep, and the use of novel object recognition (NOR) tasks.

Evidence

direct quote[Introduction, paragraphs 1-3]

“There are cognitive dysfunctions also present in depression, which have been shown to persist even when the affective symptoms are in remission, and worsen with every depressive episode”

direct quote[Introduction, paragraph 4]

“The novel object recognition (NOR) task is a well-established and simple behavioral assay of memory that relies on rodents' natural tendency to explore novel things, without externally applied rules or reinforcement”

direct quote[Introduction, paragraph 5]

PASSReviewer 3· 95% conf

The paper clearly establishes the scientific foundation by citing prior work on depression, cognitive deficits, and sleep loss, providing a logical rationale for using the novel object recognition task and long photoperiod model, and addressing limitations of previous studies.

Evidence

direct quote[Introduction, paragraphs 1-3]

“There are cognitive dysfunctions also present in depression, which have been shown to persist even when the affective symptoms are in remission... Insomnia, poor sleep quality, and altered sleep architecture are well-known characteristics of depression.”

direct quote[Introduction, paragraph 4]

“Animal investigations of depression-related cognitive deficits have applied tasks involving aversive or reinforcing stimuli, but, in humans, depressed patients show altered processing of punishment and reward cues... Therefore, these tasks could report learning and memory deficits that are actually due to altered punishment and reward processing.”

direct quote[Introduction, paragraphs 5-6]

“The NOR task is well-suited for studying depression-related cognition, because it does not employ any emotional responses, thus providing a relatively clear measure of memory and cognition.”

The paper does not describe how rats were assigned to groups (no randomization method), does not report a sample size calculation, does not pre-specify inclusion/exclusion criteria or outlier handling, and does not distinguish biological from technical replicates. Blinding is mentioned only for video scoring (EPM/FST), not for the experimenters conducting the procedures. The control group (NPP) is present but no positive control is included. No independent replication is reported.

Sub-criteria

controlsINADEQUATE

power analysisNOT REPORTED

blinding levelsINADEQUATE

outlier handlingNOT REPORTED

randomization unitNOT REPORTED

inclusion exclusionNOT REPORTED

randomization methodNOT REPORTED

replicate distinctionNOT REPORTED

independent replicationNOT REPORTED

Per reviewer (3) — the votes behind the verdict

FAILReviewer 1· 95% conf

The study design lacks essential rigor elements: no randomization method, power analysis, inclusion/exclusion criteria, outlier handling, or independent replication are reported, and blinding is only partially described.

Evidence

paraphrase[Methods, 'Experimental design']

“The paper states 'The 16 rats were separated into two groups of eight' without describing how they were assigned.”

direct quote[Methods, 'Analysis and statistics']

“An investigator blinded to the experimental conditions scored each video.”

absence[Methods, 'Experimental design']

No power analysis or sample size justification is provided.

WARNReviewer 2· 85% conf

The study design is generally sound but lacks a power analysis, randomization method, and blinding for the NOR scoring (though EPM/FST scoring was blinded).

Evidence

absence[Methods, Experimental design]

No randomization method or unit is described for group assignment.

direct quote[Methods, Analysis and statistics]

“An investigator blinded to the experimental conditions scored each video.”

absence[Methods]

No power analysis is reported.

FAILReviewer 3· 90% conf

The study design lacks critical rigor elements: no randomization method, no power analysis, no inclusion/exclusion criteria, no outlier handling, no replicate distinction, and no independent replication. Only blinding and the use of a control group are adequately reported.

Evidence

direct quote[Materials and Methods, Experimental design]

“The 16 rats were separated into two groups of eight: a normal photoperiod (NPP) control group and a long photoperiod (LPP) group.”

direct quote[Materials and Methods, Analysis and statistics]

“An investigator blinded to the experimental conditions scored each video.”

absence[Materials and Methods]

No power analysis, inclusion/exclusion criteria, or outlier handling is reported.

The paper reports that subjects were adult male Wistar rats weighing 250-275g. Species/strain and source are stated. Housing conditions (temperature, light cycle, cage-level lux) are described, but enrichment is not mentioned. Sex is reported but not justified (single-sex study). Demographics are not applicable (animal study).

Sub-criteria

demographicsN/A

sex reportedADEQUATE

sex justifiedNOT REPORTED

age weight healthADEQUATE

housing conditionsINADEQUATE

species strain sourceADEQUATE

Per reviewer (3) — the votes behind the verdict

WARNReviewer 1· 85% conf

Sex, age, weight, and housing conditions are reported, but the source of the rats is not given, health status is not explicitly stated, and the use of only male rats is not justified.

Evidence

direct quote[Methods, 'Subjects and housing']

“The subjects were 16 adult male Wistar rats”

absence[Methods, 'Subjects and housing']

The justification for using only males is not provided.

direct quote[Methods, 'Subjects and housing']

“Ambient temperatures were maintained at 25–27°C and, unless otherwise specified, animals were kept in a 12L:12D cycle (lights on at 6:00 am, lights off at 6:00 pm).”

WARNReviewer 2· 90% conf

Sex, age/weight, and species/strain are reported, but housing conditions are partially described and no justification is given for using only male rats.

Evidence

direct quote[Methods, Subjects and housing]

“The subjects were 16 adult male Wistar rats, weighing between 250-275g”

direct quote[Methods, Subjects and housing]

“Ambient temperatures were maintained at 25–27°C and, unless otherwise specified, animals were kept in a 12L:12D cycle (lights on at 6:00 am, lights off at 6:00 pm). While lights were on, light at cage levels was between 200–250 lux.”

absence[Methods]

No justification for using only male rats.

WARNReviewer 3· 85% conf

Sex and housing conditions are adequately reported, but age/weight/health is incomplete (only weight given), species/strain source is missing, and no justification is provided for using only males.

Evidence

direct quote[Materials and Methods, Subjects and housing]

“The subjects were 16 adult male Wistar rats”

direct quote[Materials and Methods, Subjects and housing]

“housed individually in a home cage with ad libitum access to food and water. Ambient temperatures were maintained at 25–27°C and, unless otherwise specified, animals were kept in a 12L:12D cycle... While lights were on, light at cage levels was between 200–250 lux.”

absence[Materials and Methods]

No justification for single-sex study.

The paper explicitly states that all procedures were approved by the University of Tennessee Animal Care Committee (Protocol Number: 2349-UTK) and were performed in accordance with the NIH Guide. This meets the criteria for adequate reporting of animal ethics and regulatory compliance.

Sub-criteria

iacuc statementADEQUATE

informed consentN/A

irb ethics statementN/A

regulatory complianceADEQUATE

Per reviewer (3) — the votes behind the verdict

PASSReviewer 1· 95% conf

The study provides a named ethics committee approval with a protocol number and states compliance with the NIH Guide for the Care and Use of Laboratory Animals.

Evidence

direct quote[Methods, 'Experimental design']

“All procedures were performed in accordance with the NIH Guide for the Care and Use of Laboratory Animals and approved by the University of Tennessee Animal Care Committee (Protocol Number: 2349-UTK).”

PASSReviewer 2· 95% conf

Ethical approval is explicitly stated with a named committee and protocol number, and regulatory compliance is mentioned.

Evidence

direct quote[Methods, Experimental design]

PASSReviewer 3· 95% conf

The study provides a named animal ethics committee approval with a protocol number and states compliance with the NIH Guide for the Care and Use of Laboratory Animals.

Evidence

direct quote[Materials and Methods, Experimental design]

“All procedures were performed in accordance with the NIH Guide for the Care and Use of Laboratory Animals”

The paper identifies the NOR objects as 'Geosolids, Learning Resources, Vernon Hills, Illinois, USA' but no catalog number. EthoVision XT and Observer XT software are named with vendor and location. GraphPad Prism is named. No antibodies, cell lines, or organisms beyond the rat strain are used. The investigational product (LPP exposure) is not a drug/device, so reagents_identified is not applicable.

Sub-criteria

mycoplasma testingN/A

reagents identifiedN/A

organisms identifiedADEQUATE

antibodies identifiedN/A

cell line authenticationN/A

software tools identifiedADEQUATE

Per reviewer (3) — the votes behind the verdict

FAILReviewer 1· 80% conf

Key resources are inadequately identified: the source of the rats is missing, and the software versions are not provided.

Evidence

absence[Methods, 'Subjects and housing']

The rat source is not provided.

direct quote[Methods, 'Analysis and statistics']

“All of the NOR videos were scored using EthoVision XT software (Noldus Information Technology, Wageningen, The Netherlands)”

WARNReviewer 2· 85% conf

Software tools are identified with versions, but key resources like the NOR objects (Geosolids) lack catalog numbers, and no RRIDs are provided.

Evidence

direct quote[Methods, Novel object recognition]

“The objects used in the NOR task were brightly colored geometric shapes (Geosolids, Learning Resources, Vernon Hills, Illinois, USA)”

direct quote[Methods, Analysis and statistics]

“All of the NOR videos were scored using EthoVision XT software (Noldus Information Technology, Wageningen, The Netherlands)”

direct quote[Methods, Analysis and statistics]

“Statistical analyses were performed using GraphPad Prism (GraphPad Software, Inc., La Jolla, California, USA).”

WARNReviewer 3· 80% conf

Software tools are adequately identified, but the organism source is not reported, and other biological resources are not applicable. Only 1 of 2 applicable criteria are adequate.

Evidence

direct quote[Materials and Methods, Analysis and statistics]

“All of the NOR videos were scored using EthoVision XT software (Noldus Information Technology, Wageningen, The Netherlands)... EPM and FST videos were manually scored using Observer XT software (Noldus Information Technology, Wageningen, The Netherlands)... Statistical analyses were performed using GraphPad Prism (GraphPad Software, Inc., La Jolla, California, USA).”

direct quote[Materials and Methods, Subjects and housing]

“The subjects were 16 adult male Wistar rats”

The paper names the statistical tests used (unpaired t-test, two-way ANOVA, one-way ANOVA with Tukey's post-hoc) and reports exact p-values and degrees of freedom. However, no verification of normality or equal variance is provided, no effect sizes or confidence intervals are reported, and the data are shown as bar graphs with error bars (SEM) rather than individual data points. The statistical software is identified (GraphPad Prism).

Sub-criteria

tests namedADEQUATE

exact p valuesADEQUATE

effect sizes ciNOT REPORTED

data presentationINADEQUATE

software identifiedADEQUATE

assumptions verifiedNOT REPORTED

mathematical plausibilityPASS

Per reviewer (3) — the votes behind the verdict

WARNReviewer 1· 85% conf

Statistical tests are named and exact p-values are reported, but assumptions are not verified, effect sizes or confidence intervals are missing, and data are presented as bar graphs without individual points.

Evidence

direct quote[Methods, 'Analysis and statistics']

“The FST and EPM behavioral data of the NPP and LPP groups were compared using unpaired t-tests”

absence[Methods, 'Analysis and statistics']

Assumptions of tests are not addressed.

direct quote[Results, paragraph 1]

“t = 0.11, df = 14, p = 0.91”

WARNReviewer 2· 80% conf

Statistical tests are named, software is identified, and data presentation includes individual points and error bars, but exact p-values are not always reported (e.g., 'p < 0.05'), assumptions are not verified, and effect sizes/confidence intervals are absent.

Evidence

direct quote[Methods, Analysis and statistics]

“The FST and EPM behavioral data of the NPP and LPP groups were compared using unpaired t-tests”

direct quote[Results, paragraph 2]

“p < 0.05”

absence[Methods]

No verification of test assumptions is reported.

WARNReviewer 3· 85% conf

Statistical tests are named and software is identified, but assumptions are not verified, effect sizes and confidence intervals are not reported, exact p-values are sometimes given as inequalities, and data presentation lacks individual data points. Plausibility checks pass.

Evidence

direct quote[Materials and Methods, Analysis and statistics]

“The FST and EPM behavioral data of the NPP and LPP groups were compared using unpaired t-tests... Two-way ANOVAs were also used to compare the object exploration times... One-way ANOVAs (Tukey’s multiple comparisons tests) were performed to compare data both within and between groups.”

direct quote[Results]

“t = 0.11, df = 14, p = 0.91... F (1,14) = 6.94, p = 0.02... p > 0.05”

absence[Materials and Methods, Analysis and statistics]

No verification of statistical assumptions.

The paper does not include any statement about data or code availability. There is no mention of a repository, accession numbers, or a public code repository. The data and analysis code are not accessible.

Sub-criteria

code sharingNOT REPORTED

accession numbersNOT REPORTED

repository depositNOT REPORTED

data availability statementNOT REPORTED

Per reviewer (3) — the votes behind the verdict

FAILReviewer 1· 95% conf

No data availability statement, repository deposit, accession numbers, or code sharing are provided.

Evidence

absence[Entire paper]

No data availability statement is present.

absence[Entire paper]

No code sharing is mentioned.

FAILReviewer 2· 95% conf

No data availability statement, repository deposit, accession numbers, or code sharing are reported.

Evidence

absence[Entire paper]

No data availability statement is present.

absence[Entire paper]

No repository deposit or accession numbers are mentioned.

absence[Entire paper]

No code sharing is mentioned.

FAILReviewer 3· 90% conf

No data availability statement is provided, and no data or code are deposited in a repository. The only applicable criterion is not reported.

Evidence

absence[Entire manuscript]

No data availability statement found.

The methods are described in sufficient detail to allow replication. The paper reports all measured outcomes, including non-significant results. Limitations are discussed (e.g., photoperiod shift vs. circadian disruption, testing during light cycle). The conclusions are proportional to the evidence. The funding source is provided (NIH grant MH59839), but no conflict of interest statement is included. The paper does not reference a reporting guideline (e.g., ARRIVE).

Sub-criteria

funding coiINADEQUATE

trial registrationN/A

reporting guidelineNOT REPORTED

methods completenessADEQUATE

all outcomes reportedADEQUATE

limitations discussedADEQUATE

conclusions proportionalADEQUATE

Per reviewer (3) — the votes behind the verdict

PASSReviewer 1· 85% conf

Methods are detailed, all outcomes are reported, limitations are discussed, conclusions are proportional, and funding is acknowledged, though a conflict of interest statement is missing.

Evidence

paraphrase[Methods, entire section]

“The methods describe housing, NOR protocol, EPM, FST, TSD, and analysis in detail.”

direct quote[Discussion, paragraph 6 and 7]

“We acknowledge that this study did not address any behavioral differences that could have been seen between the rats’ light and dark cycles, because all tests were performed during the animals’ light cycle.”

absence[End of paper]

No conflict of interest statement is provided.

WARNReviewer 2· 85% conf

Methods are detailed enough for replication, limitations are discussed, and conclusions are proportional, but no trial registration or reporting guideline is mentioned, and funding/COI is partially reported.

Evidence

direct quote[Methods, Novel object recognition]

“The NOR procedure consisted of a habituation phase, a familiarization phase, and a testing phase.”

direct quote[Discussion, paragraph 4]

“We would like to acknowledge that it is possible that LPP exposure produces changes in sleep behavior that buffer against the effects of sleep deprivation.”

direct quote[Acknowledgments]

“This work is supported by National Institutes of Health Research Grant (MH59839).”

PASSReviewer 3· 85% conf

Methods are detailed, all outcomes are reported, limitations are discussed, and conclusions are proportional. However, no reporting guideline is referenced, and the funding/COI statement lacks a conflicts-of-interest declaration.

Evidence

direct quote[Materials and Methods, Novel object recognition]

“The NOR procedure consisted of a habituation phase, a familiarization phase, and a testing phase. Each phase of the NOR procedure began on separate, sequential days at 10:00 am.”

direct quote[Discussion, paragraphs 5-7]

“It is possible that the cognitive deficits seen in long-photoperiod exposed rats are due to photoperiod shift and not to a depressive phenotype... We acknowledge that this study did not address any behavioral differences that could have been seen between the rats’ light and dark cycles”

absence[Entire manuscript]

No reporting guideline is referenced.

21 copyedit issues flagged (1 major): mostly typo, other, consistency.

Checked 93 references: 92 verified — 1 not checked.

Αlpha¹ Rigor Action ItemsFinal pass before journal submission

This published paper has moderate robustness. An informed reader should weigh the lack of randomization and blinding details, the missing data availability, and the internal contradiction in the Results (claiming significance with p>0.05) as potential concerns that could warrant a correction or independent re-analysis.

1.
HIGHrigor
Correct the internal contradiction in the Results section where the LPP group's RI after TSD is described as 'remained significantly lower' but the reported p-value is 'p > 0.05'.
This is a direct contradiction that undermines the validity of a key finding and would be flagged by any reviewer or reader.
2.
HIGHdata code
Add a data availability statement and deposit raw data (e.g., NOR exploration times, FST scores) in a public repository such as Figshare or Zenodo, providing accession numbers.
The complete absence of data sharing is a major transparency gap that prevents verification and reuse.
3.
HIGHrigor
Describe the randomization method used to assign rats to groups (e.g., random number generator) and the unit of randomization in the Methods section.
Without randomization, the study's internal validity is compromised and group differences may be confounded.
4.
HIGHrigor
Include an a priori power analysis or sample size justification in the Methods section.
The choice of n=8 per group is not justified, raising concerns about the study's ability to detect meaningful effects.
5.
HIGHrigor
Report blinding procedures for the experimenters conducting the behavioral tests, not just for video scoring, in the Methods section.
Incomplete blinding introduces potential bias in data collection and interpretation.
6.
HIGHreporting
Add a conflicts-of-interest statement (e.g., 'The authors declare no competing interests') in the Acknowledgments or a separate section.
A missing COI statement is a standard reporting requirement and its absence is a transparency gap.
7.
HIGHstatistics
Report exact p-values for all comparisons (replace inequalities like 'p < 0.05' with exact values) and include effect sizes with confidence intervals.
Inequality p-values and missing effect sizes limit the interpretability and reproducibility of the findings.
8.
MEDIUMrigor
Pre-specify inclusion/exclusion criteria for the animals and define how outliers will be handled in the Methods section.
Without pre-specified criteria, the analysis is vulnerable to post-hoc decisions that can bias results.
9.
MEDIUMreporting
Mention adherence to a reporting guideline such as ARRIVE in the Methods section.
Referencing ARRIVE is standard for animal studies and improves completeness and transparency.
10.
MEDIUMrigor
Provide a scientific justification for using only male rats, or acknowledge this as a limitation in the Methods or Discussion.
Single-sex studies without justification limit generalizability and are a common reviewer concern.
11.
MEDIUMreporting
Report the source (vendor) of the Wistar rats and any genetic background information in the Subjects and housing section.
The source of animals is essential for reproducibility and for assessing potential genetic or health confounds.
12.
MEDIUMstatistics
Verify statistical assumptions (normality, equal variance) for each test and report actions taken if violated, in the Analysis and statistics section.
Unverified assumptions can invalidate the chosen statistical tests and lead to incorrect conclusions.
13.
MEDIUMstatistics
Present individual data points in figures (e.g., scatter plots) alongside summary bars, and define error bars clearly.
Bar graphs alone obscure the distribution and variability of the data, which is critical for small sample sizes.
14.
LOWcopyedit
Fix the typo 'Abbreviaions' to 'Abbreviations' in the captions of Figures 2, 3, and 4.
Consistent spelling improves professionalism and readability.
15.
LOWcopyedit
Remove the stray '1' and repeated title in the Introduction first line.
This formatting error detracts from the paper's presentation.

Full text (67,285 chars)Analyzed: Jul 6, 2026

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