PONE-D-24-41991Regular physical activity affects brain activities in old individuals: an observational studyPLOS ONE

Dear Dr. Shigihara,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

I received contrasting opion from reviewers. The prevalent opinion, including my own, is tat tha manuscript needs substantial revisions. Criticism, however, mainly affects the description (completeness, clarity) of methods and statistical teratment. This is within the limits of a major revision. Please address all the comments by reviewers regarding methodology and also other aspects, including coherence bethween results and interpretation.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Partly

Reviewer #5: No

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: No

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: No

Reviewer #5: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The manuscript described whether the repeated physical activities affect the aged people’s brain function or not. The authors divided the 327 patients in memory clinic into activity group and non-activity group, and measured the brain function using MEG as well as psychological tests. They found the promising results by repeated activity improving the cognitive functions as well as the good outcome in the future.

There are several problems in this manuscript.

1) The design of the study is not prospective, just retrospective transverse research. Therefore, there is a problem suggesting the reverse results; the high cognitive function people tend to perform more physical activities. Furthermore, this study was done in one institute, then the bias of the subjects could not be avoided. One suggested plan is that the repeated research on different subjects might be more stronger influences on this result.

2) Confounding factors such as diet, social activities, educational level may affect the cognitive functions.

3) In my experience, the relationship between MEG results and cognitive function is considered to be difficult to understand.

4) Data availability is not clearly written. DOI is not effective.

Reviewer #2: The paper statistically evaluates correlation of personal physical activity status, cognitive level and values of brain activity of large old-age population.

Compliance with criteria of PLOS ONE.

The study presents the results of primary scientific research – Yes

Results reported have not been published elsewhere – I trust the authors.

Experiments, statistics, and other analyses are performed to a high technical standard and are described in sufficient detail – Not really, see my detailed comments below.

Conclusions are presented in an appropriate fashion and are supported by the data – So, so.

The article is presented in an intelligible fashion and is written in standard English – The authors used a specialized profiling firm to edit their English text (see l. 326-327).

The research meets all applicable standards for the ethics of experimentation and research integrity – Yes

The article adheres to appropriate reporting guidelines and community standards for data availability – Yes. See l. 348-350.

Detailed comments and notes

1) Can the authors provide references to explanations of values MF, IAF, SSE (l. 84).

2) Abbreviations in main text differ from those in the abstract (34-38) For example, in the abstract you note MMSE-J, but in the text just MMSE (53).

3) 7, 111 – give corresponding statistics for men, especially statistics of age.

4) 134-140. You here mention about special Japanese variant of corresponding scores. I think, you should provide concise description of differences them from international. In this context you should change abbreviations in the abstract.

5) 153 – abbreviation “meg” must be in uppercase.

6) In Methods you should describe hardware used for MEG abduction, protocol of this procedure, bands and channels you used for future analysis. The paper has complete lack of this technical information.

7) I suppose a good idea would to provide short mathematical description of all parameters you analyze (MF, IAF, SSE).

8) 160-165. Provide mathematical formula for SOC value.

9) 173 – abbreviation “meg” must be in uppercase.

10) 171 – 174. You write about significant differences in values. I think, you may provide here statistical results (p=…, etc.) mentioning the statistical method of evaluation.

11) 181. Please provide more informative header of the table. What is P(unk)? In the text above (l. 173-179) you mention Spearman’s rank correlation but the table doesn’t provide any information about it. By the way the Table 1 provides information about groups of patients. I think you should include one more table with result of Spearman’s rank correlation analysis.

12) Again, 188 - abbreviation “meg” must be in uppercase. Please look through the text and correct this error.

13) 188-191. Excuse me but I see no strong correlation between age and scores. There mostly are horizontal linear regression lines. I am strongly against “ritual” phrases in statistical reports (l. 191). If you mention ANOVA you should describe statistical model, you used, like one-way, two-way, repeated measurement and so on. Statistical results should have F and p values and information about post-hoc estimation of pair-wise comparison.

14) 202-209. From the text and table, I deduce that you use two-way ANOVA with two main factors 1) MEG value and 2) RPA to assess their influence on score parameter. I think, you should describe it in the text. Why do you not analyze the group of activity as impact factor?

15) 210. Title of the table is bad. It describes statistical method. I think the title could give the reader idea what is estimated by the table. I would propose something from your text “Assessing the effects of regular physical activity on MEG spectral parameters”. And statistical method you could describe somewhere in Table note below.

16) Better idea to introduce and describe Fig 2 in Results.

Reviewer #3: This manuscript is of interest for the general audience of PLOS One. I believe that it is well structured and reads very well. I have a few comments (please see below) which I hope that the authors can clarify in a revised version.

Can the authors provide more details on the data acquisition (experimental paradigm and recordings= specifications) as well as the preprocessing (e.g., filtering) of the MEG data? The manuscript does not contain any information on this apart from descriptions on the three spectral outcomes.

The authors write that patients were classified as either ‘active’ or ‘nonactive’. The definition seems quite vague as it seems that patients reported these exercise levels themselves. Was this standardised in any way? For example, can the authors be more precise on what was meant with being physically active? Did the patients need to meet any criteria to be labelled active (e.g., in terms of frequency or duration)? Similarly, is it possible to have a more precise definition on what is meant with being 'nonactive'? If this is the most detailed information that the authors can provide, how sure are they that the ‘active’ and ‘nonactive’ groups are defined correctly?

Minor comments

Line 154: meg -> MEG

Line 173: meg -> MEG

Line 171 and 181: How is it possible that the p-values are different between the in-text report (line 171; p = 0.647) and Table 1 (line 181; p = 0.305)?

Line 181 (Table 1): Can the authors please report test statistics, degrees of freedom and effect sizes for these statistical contrasts?

Line 188: meg -> MEG

Reviewer #4: Fukasawa et al. conducted a retrospective study on a large group of patients referred to their dementia clinic. They categorized the patients into active and inactive groups based on their routine physical activity and compared their cognitive scores as well as MEG spectral parameters. Their findings suggested that patients who engaged in regular physical activity tended to have higher cognitive scores.

While I read the submitted manuscript with interest, it requires significant revisions to improve clarity, coherence, and scientific rigor. Below are detailed suggestions for each section of the manuscript:

Introduction

o The purpose of the first paragraph is unclear. Is it intended to define dementia, explain why specific tests were used, or discuss the difficulty of predicting cognitive decline in dementia patients? Clarify the focus.

o The opening sentence of the second paragraph makes a broad claim but lacks references to support it. Provide appropriate citations.

o The concept of "functional reserve" should be explained before introducing it.

o This paragraph appears to discuss the role of physical activity, but the connection to cognitive reserve is unclear. Use examples that directly relate to cognitive reserve (e.g., mental stimulation, education) rather than unrelated analogies like kidney/liver functions.

o Explain the physiological mechanisms by which physical activity might prevent cognitive decline, with appropriate references to support these claims.

o In the third paragraph the claim that electrophysiological measurements do not correlate well with cognitive assessment may reflect issues with the measurements themselves, not necessarily the impact of cognitive reserve due to physical activity. Avoid oversimplified assumptions and provide a robust explanation.

o Explain how spectral measurements are proposed to demonstrate cognitive reserve. Clarify why cognitive reserve might not directly improve cognitive performance but could indirectly affect spectral measures.

o The hypothesis that electrophysiological activity represents both functional reserve (via physical activity) and cognitive state independently is unclear. Provide a logical connection between these concepts and how they are tested in this study.

o Overall, the introduction would benefit from a more coherent structure, improved clarity, and a less exaggerated presentation of the hypothesis.

Methods

1. Dataset:

o Define the threshold used to classify participants as cognitively healthy.

2. Parameters:

o Avoid claiming that "these parameters are established in clinical practice" if this assertion is based on a single study, and a case serios, particularly if conducted by the same group. Broader validation is necessary to support this statement.

o Define "regular exercise routine" explicitly. Was this based on general responses (e.g., "Do you exercise regularly?") or specific criteria (e.g., "Do you walk 30 minutes at least three times per week?"). If the former, this grouping may lack reliability.

3. Statistics:

o Justify the use of Wilcoxon tests. For a dataset of this size, a t-test or ANOVA would be more appropriate and straightforward.

4. MEG analysis:

o There were no mention of how the analysis of MEG data have been done, the preprocessing of the data as well as the calculation of spectral parameters should be explained in details.Results

1. Correlations:

o The manuscript reports significant correlations between cognitive scores and cognitive measures, as well as between MEG measures and MEG measures, but fails to explore correlations across these domains (e.g., MEG measures with cognitive scores). This should be addressed.

2. Evaluation of Regression Models and Physical Activity Effect:

o These two sections are unclear to me. Clarify the methods and results to make the findings interpretable.

Discussion:

• The statement that "[MEG spectral parameters] indicate a functional reserve that may help prevent future cognitive decline, regardless of the current cognitive state" is not supported by the findings. How was cognitive reserve measured in this study?

• The conclusions drawn from the results are overgeneralized and not sufficiently supported. Avoid overinterpreting simple correlations.

• The discussion is overly focused on functional reserve, a concept that appears unrelated and untested within the study. This weakens the narrative and risks misrepresentation of the findings.

General Comments

• To demonstrate that physical activity prevents cognitive decline, the study should begin by establishing a correlation between the amount of physical activity and cognitive scores or show a significant difference in cognitive scores between active and inactive groups. The relevance of MEG measurements is unclear in this context.

• To support the claim that physical activity prevents cognitive decline, the manuscript should first establish a direct correlation between physical activity and cognitive scores. Alternatively, compare cognitive scores between physically active and inactive groups.

• The inclusion of MEG measurements seems disconnected from the primary research question. If MEG is to be used, consider using logistic regression to predict activity status (active vs. inactive) based on MEG and cognitive measures. Then, test whether including MEG measurements improves predictive power.

• Simplify statistical analyses. The use of overly complex models for simple comparisons detracts from clarity and accessibility.

Conclusion

The manuscript has potential but requires substantial revisions to address the issues outlined above. The introduction needs a more focused narrative, the methods and statistical analyses need better justification, and the results should be clarified and aligned with the hypotheses. Furthermore, the conclusions should be restrained to reflect the actual findings without overstating their implications.

Reviewer #5: In this study, Fukasawa and colleagues investigated whether electrophysiological brain activity can reflect the preventative effect of regular physical activity against cognitive decline. The authors combine records of regular physical activity, with neurophysiological recordings obtained using Magnetoencephalography (MEG) and neuropsychological assessments of cognitive function. Regression analyses were used to investigate the effect of physical activity and age on the three spectral MEG parameters. The study also aimed to disentangle the contribution of physical activity to brain signals and neuropsychological assessments. While I commend the authors for investigating such an interesting and complex phenomenon, there are serious issues that prevent me from recommending publication of this work. The following is a summary of the most important issues:

Major issues:

1. The manuscript lacks any kind of detail about how MEG data was collected, preprocessed and analyzed. Without such information, it is impossible to establish whether MEG data has been treated according to scientific conventions and whether the MEG analysis pipeline could have influenced the current results. Because MEG spectral measures are a central part of the current study, the authors should have included a detailed subsection to within their methods section explaining each step in the MEG data analysis pipeline. Such section should include, among other things: the MEG system used, the manufacturer, whether online filters were applied, what instructions were given to participants, whether data was acquired in eyes-closed or eyes-open resting-state conditions, what package was used to analyze MEG data, off-line filters, procedures to identify bad channels or noisy segments, whether these were manual or automatized, whether data was epoched or not, and if so, what was the epoch’s duration, whether epochs were rejected, and if so, what epoch rejection thresholds or parameters were used, the total number of epochs before and after epoch rejections per individual, among others.

Similarly, regarding MEG data analysis, the authors need to provide a detailed description of how spectral parameters were obtained, describing all relevant steps, methods, tools used in their signal-processing pipeline and mathematical formulas (if necessary). For instance, it is not clear what type of method was used to compute the spectral representation of the time-domain signal, what parameters were set for such analysis, and how the spectral measures were subsequently estimated. An example of how to report both MEG preprocessing and spectral analyses can be found in references 20 and 23 of the manuscript, or in other similar papers by that same group.

2. There are serious issues with how statistical analyses are reported. For instance, the authors report their correlation analyses and direct the reader to table 1 [line 179], but I believe table 1 actually presents the results of the Wilcoxon Signed Rank Tests. Relatedly, the authors state that Fig 1 shows the regression analyses [line 188], but the title of Fig1 indicates these scatter plots represent the correlation between spectral parameters and neuropsychological assessment. It is therefore unclear what analysis figure 1 actually shows.

The regression analyses must be described and reported in full detail, but instead, the authors provide almost no information about the results of their regression analyses in their result section, other than referring the reader to figure 1. First of all, authors need to explicitly state how models were specified (provide their formulas). For instance, the author’s state:

“We then assessed the effect of regular physical activity on meg spectral parameters while accounting for cognitive state. Each meg spectral parameter (MF, IAF, and SSE) was subjected to a multiple regression model with three predictors: (1) a categorical predictor of regular physical activities (‘Active’ and ‘Nonactive’), (2) age or one of the neuropsychological assessment scores (MMSE-J, FAB-J, or ADAS-J cog) as a covariate, and (3) their interaction term.” [Lines 152-157].

Based on this, I would assume that the models took the form:

y ~ RPA + AGE + RPA*AGE

y ~ RPA + MMSE-J + RPA*MMSE-J

y ~ RPA + FAB-J + RPA*FAB-J

y ~ RPA + ADAS-J + RPA*ADAS-J

This is just an assumption, and I do not know if this is correct, which illustrates the problem: there is very little information about how many models were designed and how they were specified. Without this information, it is very difficult to assess whether models were appropriate and whether the author’s interpretation of their results are justified.

Regression tables could be used to summarize the results, illustrating whether the effect of each term within each model is actually significant or not. Alternatively, this information could be presented within the text. Regardless, it is crucial that the reader understands whether factors or their interaction have a significant effect in predicting changes in the dependent variable. Such information, however, is not provided.

3. To properly evaluate model performance, authors should also report metrics of goodness-of-fit for each model, such as R2, AIC, or BIC for each model. Unfortunately, none of these values are reported. The authors report SOC (Size of Contribution) as a measure of how much one factor contributes to model performance, but this is not enough to back up the interpretations they derive from their regression analyses in their discussion section. I am also having difficulties understanding table 2. The authors state that

“To evaluate the regression models assessing the effects of regular physical activity on MEG spectral parameters while accounting for age or one of the neuropsychological assessment scores, we performed an ANOVA (Table 2)”.

Based on this, I would expect a stepwise model comparison procedure where covariates are sequentially added to initial models and then the statistical effect of adding such covariates is assessed via maximum likelihood estimation. Instead, the authors present table 2 as a summary of their model comparison procedure. However, it is difficult to understand from table 2 how models were compared and how the effect of covariates was assessed. Actually, table 2 gives the impression that spectral parameters were treated as predicting (i.e. independent) variables because they are reported with associated F and p values, as if they were factors within a new set of independent models. It is therefore not clear how different models were compared, or how the presence or absence of their covariates of interest affected their models.

4. A somehow worrisome issue at the conceptual level is the use of ambiguous terminology in the introduction. Throughout this section, the authors use two concepts, functional reserve and cognitive reserve, which are not mutually interchangeable. Functional reserve is physiologically quantifiable, while cognitive reserve is behaviorally, rather than physiologically quantifiable. I understand the authors attempt to establish a parallelism between functional and cognitive reserve. However, in later sections of the manuscript, it remains unclear whether the authors are empirically concerned with functional reserve (which might be quantifiable via MEG), cognitive reserve (which would be quantifiable via neuropsychological assessment), or both. What is more, the authors later state:

“We hypothesized that electrophysiological brain activity would represent both the amount of functional reserve (i.e., regular physical activity) and the current cognitive state independently” .

This implies that regular physical activity is their operationalization of functional reserve. Such a lack of conceptual clarity makes it difficult to connect relevant concepts with their operationalized independent variables of interest. Along with the aforementioned issues in how regression models are specified and reported, it is very difficult to assess the validity of the interpretations offered by authors in the discussion section of their work.

Other issues

1. It would be useful if the authors offered a more detailed description of “cognitive states”, especially considering the broad scope of the journal. I assume that when they use the term “cognitive state”, they refer to the clinical assessment of multiple cognitive functions such as attention, memory, alertness, among others, as quantified by clinically-validated neuropsychological questionnaires and assessment tools.

2. The authors are right that MEG measures the magnetic fields produced by the electrophysiological activity of populations of neurons in the cerebral cortex, but it is inaccurate to state that MEG reflects dementia-associated cognitive states [Lines 79-81]. MEG cannot directly reflect cognitive states, but rather, provide measures of brain function that might (or might not) be indicative of those states. Relatedly, while the authors do well in justifying their three spectral measures of interest, they should explicitly acknowledge that these here are just a few among many more parameters and measures of brain function that can be obtained using MEG.

3. The authors state that “This study revealed that regular physical activity significantly influenced electrophysiological brain activity while controlling for the current cognitive state (i.e., neuropsychological scores). This influence was significant across any neuropsychological assessment scores considered”, but considering the lack of clarity on MEG and statistical analysis, it is hard to see how they arrived at this conclusion. This might also be an overinterpretation of their results, particularly because MEG-measured brain dynamics during resting state are known to be influenced by a myriad of genetic and environmental factors, which are not controlled within the current experimental design.

4. In the same vein, an important covariate that the authors did not include in their analyses was educational attainment. This is important because the authors cite previous research linking educational attainment with cognitive reserve (Stern et al. 1992), and previous studies investigating the effect of physical activity on MEG-measured brain activity have in fact included educational attainment as a control variable (de Frutos-Lucas et al. 2018).

de Frutos-Lucas, J., López-Sanz, D., Zuluaga, P., Rodríguez-Rojo, I. C., Luna, R., López, M. E., Delgado-Losada, M. L., Marcos, A., Barabash, A., López-Higes, R., Maestú, F., & Fernández, A. (2018). Physical activity effects on the individual alpha peak frequency of older adults with and without genetic risk factors for Alzheimer’s Disease: A MEG study. Clinical Neurophysiology, 129(9), 1981–1989. https://doi.org/10.1016/j.clinph.2018.06.026

Stern Y, Alexander GE, Prohovnik I, Mayeux R. Inverse relationship between education and

402 parietotemporal perfusion deficit in Alzheimer’s disease. Ann Neurol. 1992 Sep;32(3):371–5.

5. The last paragraph of the discussion section where the authors discuss why some patients in the active group use functional reserve to improve their current cognitive state [lines 287-305] is highly speculative, as claims are not directly related to or backed up by the authors’ results. Particularly, lines 298-305 present an oversimplification of how electrophysiological neural dynamics are generated and linked to brain disease. Many of these claims need to be toned down.

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Reviewer #5: No

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PONE-D-24-41991R1Regular physical activity affects brain activities in old individuals: an observational studyPLOS ONE

Dear Dr. Shigihara,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Reviewers generally appreciated the authors' efforts to clarify the methods and improve the coherence of the manuscript. However, there is still substantial ambiguity regarding a crucial part of the methods—specifically, the inclusion criteria and the population studied. One reviewer highlighted that the tests used may not be appropriate for healthy aging subjects. It remains unclear whether a mix of healthy subjects and patients with dementia was studied, and if so, what the rationale was for this selection. Please clearly specify the population studied, including diagnoses, and clarify the reasoning behind the choice of tests. Note that the manuscript may not be accepted if the population selection is not coherent with the study’s aim and relevant methods

Please submit your revised manuscript by Apr 24 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols .

We look forward to receiving your revised manuscript.

Kind regards,

Federico Giove, PhD

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

Reviewer #3: All comments have been addressed

Reviewer #5: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #5: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #5: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #5: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #5: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The manuscript described the daily activities affecting the mental function in aged.

There are several problems, and among them I wold like to point out the psychological examinations; adopted tests are for the medical diagnostic test for dementia. It is necessary to measure the normal persons maintaining the brain functions, such as Wechsclar memory scale for memory, Trail making tests for attention, Barthel index for ADL and so on. The psychological examination for people of good normal life could not be evaluated by medical psychological examinations such as muse, or others.

In order to evaluate the brain integrity, it is difficult to do by MEG. In a reverse sense, it is expected that the aged brain have a MEG or EEG function on a particular pattern or not.

In my impression, the design of the study is not good for the intended purpose.

Reviewer #2: All is well. I have only two small comments.

l. 329 “ANCOVA and SOC” The title of the section does not give any information about the topic.

I think a better idea is from your text below "Effect of groups on MEG spectral parameters".

l. 357 Table 2. Results of Analysis of Covariance. I already pointed out this inaccuracy in the previous review (see comment 2-15). It is better to give the table title from your text “Assessing the effects of regular physical activity on MEG spectral parameters”. In your reply to me, you wrote that you had corrected this inaccuracy, but apparently you forgot to do so in the text.

Reviewer #3: I thank the authors for addressing my comments of the previous round. The manuscript has improved as a result. I don’t have any further comments.

Reviewer #5: Minor points

1) Line 56. Typo. Its process -> This process

2) Line 62. Typo. Influence on pathological conditions -> influence pathological conditions

3) Line 85-86. Which are sensitive to the cognitive decline -> which are sensitive to cognitive decline

4) Figure 1. Bottom left corner. Week association -> Weak association

5) Line 100. and considered drivers of cognitive impairments -> and are considered drivers of cognitive impairments

6) Line 373. These factors interfere each other -> these factors Interfere with each other

7) Lines 375 and 378 as the direct/indirect pathways -> as direct/indirect pathways

8) Line 381. From a clinical perspective it is not essential whether… -> From a clinical perspective, it is not clear whether…

9) Line 385. This study showed that MEG spectral parameters were enhanced by regular physical activity ----- Enhanced might be an inappropriate word choice here. Consider using less causal language.

10) Line 388. Contain -> Reflect

11) Line 425. Theoretically, an increase in high-frequency oscillatory activity corresponds to high MF, IAF, and SSE values. ----- This is highly speculative, as spectral parameters are jointly modulated by a myriad of neurophysiological and neuromodulatory phenomena, rather than oscillatory power within a single frequency band. I would suggest the authors to either remove this claim or substantiate it with empirical evidence.

Final comments

I would like to thank the authors for taking the time to implement the suggested corrections and submit a much-improved version of their original work. I enjoyed reading this new version and found their line of argumentation much clearer. The description of data analysis and statistical procedures is much clearer and logically responds to their research question. I also appreciate the inclusion of MEG data acquisition and preprocessing procedures. I am still somewhat confused as to why the authors chose to use SOC to quantify the effect of physical activity on predicting MEG spectral parameters, rather than more conventional methods such as mediation analyses. However, I do appreciate the mathematical and statistical explanation provided by the authors, which allowed me to understand their approach better than in the original submission. The only thing I am missing from this new version is a more careful explanation of what the different spectral parameters included in this study measure, neurophysiologically speaking (i.e., changes in excitation/inhibition ratios, changes in neuromodulator release, power ratios between different frequency bands, etc.). This would help the reader make a smoother connection between physical activity, brain physiology, and cognition.

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Reviewer #1: Yes:  OK

Reviewer #2: Yes:  Andriy Gorkovenko

Reviewer #3: No

Reviewer #5: No

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PONE-D-24-41991R2

Regular physical activity affects brain activities in old individuals: an observational study

PLOS ONE

Dear Dr. Shigihara,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we have decided that your manuscript does not meet our criteria for publication and must therefore be rejected.

Specifically:

The study suffers from significant sampling bias . The studied sample is not representative of a specific population (e.g. healthy elderly subjects, early AD, etc), but simply reflects the people that seek consulting at the involved Medical Centre. This is not a meaningful population and can’t be easily generalized.

Moreover, only in the last revision authors listed the outcome of the diagnostic path, stating that among the subjects “32 were diagnosed with healthy ageing, 60 with mild cognitive impairment, and 220 with dementia”. The sample was treated as a whole, irrespectively of health condition, and the statistical analysis contrasted active vs non-active, with no covariate related to diagnosis. Instead, neuropsychological assessments were used as covariates, and they may be inappropriate across the involved sub-populations. Irrespectively of the covariates, this approach obviously prevented the study of interactions activity x health condition. It may well be that the reported  effect is dominated by one sub-group.

Finally, the manuscript, including the title, refers generally to “old individuals”, and states that findings can be used in patients with cognitive impairment. All of these are undue generalizations, if the sampled population does not match the claims.

I’m sorry this fundamental problem was missed in the first round of reviews and was catch only during the second.

The manuscript can be resubmitted, but only if the mentioned problems are addressed. As it stands, the methods are not appropriate

I am sorry that we cannot be more positive on this occasion, but hope that you appreciate the reasons for this decision.

Kind regards,

Federico Giove, PhD

Academic Editor

PLOS ONE

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- - - - -

For journal use only: PONEDEC3

Regular physical activity affects brain activities in old individuals: an observational study

PONE-D-24-41991R3

Dear Dr. Yoshihito Shigihara,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Hiroki Annaka

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

I have re-evaluated your paper as a new Academic Editor. I have judged your paper as accepted through peer review.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The comments by reviewers were well revised and methodology (MEG, statistical analyses), as well as good described results and discussion improved, those satisfied Plos One criteria. I hope prospective study in the future will produce more fruitful results, meaning more strict scientific results anticipated.

Reviewer #2: You corrected my remarks and I have no complaints against you. I recommend that the editor publish your article.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy .

Reviewer #1: Yes:  H. Fukuyama

Reviewer #2: Yes:  Andriy V. Gorkovenko

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