Virtual reality as a tool for balance research: Eyes open body sway is reproduced in photo-realistic, but not in abstract virtual scenes

Lorenz Assländer; Stephan Streuber

doi:10.1371/journal.pone.0241479

Peer Review History

Original SubmissionJuly 29, 2020
11 Sep 2020 Decision Letter - Eric R. Anson, Editor PONE-D-20-23613 Virtual reality as a tool for balance research: eyes open body sway is reproduced in photo-realistic, but not in abstract virtual scenes PLOS ONE Dear Dr. Assländer, 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. Please submit your revised manuscript by Oct 26 2020 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: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols We look forward to receiving your revised manuscript. Kind regards, Eric R. Anson Academic Editor PLOS ONE Journal Requirements: When submitting your revision, we need you to address these additional requirements. 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Please ensure you have thoroughly discussed all potential limitations of this study within the Discussion section, including the small sample size. 3.Thank you for including your ethics statement: "The study was conducted in agreement with the declaration of Helsinki in its latest revision and in agreement with the University of Konstanz ethics regulations". Please amend your current ethics statement to confirm that your named institutional review board or ethics committee specifically approved this study. Once you have amended this/these statement(s) in the Methods section of the manuscript, please add the same text to the “Ethics Statement” field of the submission form (via “Edit Submission”). For additional information about PLOS ONE ethical requirements for human subjects research, please refer to http://journals.plos.org/plosone/s/submission-guidelines#loc-human-subjects-research. 4. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information. [Note: HTML markup is below. Please do not edit.] 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 ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 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: Yes Reviewer #2: Yes ****** 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 ****** 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: General comments This manuscript is well written and concerns a highly interesting topic, since VR is use increasingly in rehabilitation. The manuscript is well written. Please find my specific comments below. Title Explicit Abstract Clear Introduction Appropriate. Aim Long, but clear Method How were the subjects recruited? Were they healthy subjects, students, staff? How many women and men? Differences in response to immersive virtual reality environment has been found between men and women in other studies. Is there any approval from an ethical review board? Results Appropriate Discussion Line 341 – 348, “Cognitive suppression of the visual contribution”. The paragraph is interesting but needs to be in relation to the findings in this study. Only limitations of balance in VR are discussed. Please add a paragraph with strengths and limitations of the study. Conclusion Well written Tables and figures Table 1 shows within subjects differences in the different conditions, please clarify this in the heading. Also include the statistical analysis used when calculating the differences, preferably in a footnote. Table 2 also needs a clarifying heading. Abbreviations should be explained in a footnote. References Appropriate Reviewer #2: Virtual reality as a tool for balance research: eyes open body sway is reproduced in photo-realistic, but not in abstract virtual scenes The study compared the amount of postural control (body sway) between reconstructed VR environment (LAB scene) and the real world, together with comparison against other visual conditions. Authors found that postural sway was in the real world was synonymous to the LAB scene but not with eyes closed or abstract virtual scenes. They concluded that VR is a valid tool for conducting balance research. The study was well performed, well written to clearly communicate the results and has added additional evidence for the usage of VR in balance research. There are, however, a few grammatical considerations and comments needed. Introduction Line 39: The “Who” reference should read “WHO” Line 146: Change “was” to “of”. Line 146: Rephrase to clarify meaning. Check word(s) omitted in sentence beginning with “During the experiment…”, specifically, “…were while…” and “…instrumentation to measure…” Line 172: Check word(s) omitted in “from were”. Discussion Lines 330 – 339: Conducting further research to unravel why inconsistent results were found in the Menzies’ study is in order. However, the present authors could compare the nature of the visual scenes in the both studies to provide some possible reasons. For instance, the LAB scene may have resulted to a lesser postural instability compare to the ABS scene because it was a reconstruction of the real world. It is clear that this LAB scene is different from the visual disturbances in the Menzies’ study. Line 344: “(Bronstein, 1986)” should be written as “Bronstein (1986)”. ****** 6. 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: No Reviewer #2: Yes:** Kwadwo Osei Appiah-Kubi [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0241479.r001
Revision 1
14 Sep 2020 Author Response We would like to thank both reviewers for the positive feedback and their helpful remarks. Below is a point-by-point response to the comments. Reviewer #1: General comments This manuscript is well written and concerns a highly interesting topic, since VR is use increasingly in rehabilitation. The manuscript is well written. Please find my specific comments below. Title Explicit Abstract Clear Introduction Appropriate. Aim Long, but clear Method How were the subjects recruited? Were they healthy subjects, students, staff? How many women and men? Differences in response to immersive virtual reality environment has been found between men and women in other studies. Is there any approval from an ethical review board? We specified the open questions in the manuscript. We rephrased the ethics statement, now explicitly refering to the approval. New paragraph: „Ten young and healthy subjects (age 25.4 ± 4.7 years; height 171 ± 11 cm; weight 65.5 ± 12.0 kg; 5 female, 5 male) participated in the study after giving written informed consent. Exclusion criteria were orthopedic problems, balance related problems, concussions, and a history of epilepsy. Subject were recruited via an online platform where mostly University students are registered. The study was conducted in agreement with the declaration of Helsinki in its latest revision and in agreement with was approved by the University of Konstanz ethics board (IRB20KN07-004).“ Results Appropriate Discussion Line 341 – 348, “Cognitive suppression of the visual contribution”. The paragraph is interesting but needs to be in relation to the findings in this study. Thank you for pointing out that we did not describe our point properly. We clarified our statement and put it into context. Only limitations of balance in VR are discussed. Please add a paragraph with strengths and limitations of the study. We generalized the paragraph and added several aspects, such as the small number of subjects (limitation) and the strong effects we found in our results (strength). Conclusion Well written Tables and figures Table 1 shows within subjects differences in the different conditions, please clarify this in the heading. Also include the statistical analysis used when calculating the differences, preferably in a footnote. Table 2 also needs a clarifying heading. Abbreviations should be explained in a footnote. Amended as suggested. References Appropriate Reviewer #2: Virtual reality as a tool for balance research: eyes open body sway is reproduced in photo-realistic, but not in abstract virtual scenes The study compared the amount of postural control (body sway) between reconstructed VR environment (LAB scene) and the real world, together with comparison against other visual conditions. Authors found that postural sway was in the real world was synonymous to the LAB scene but not with eyes closed or abstract virtual scenes. They concluded that VR is a valid tool for conducting balance research. The study was well performed, well written to clearly communicate the results and has added additional evidence for the usage of VR in balance research. There are, however, a few grammatical considerations and comments needed. Introduction Line 39: The “Who” reference should read “WHO” Corrected. Thank you! Line 146: Change “was” to “of”. Corrected. Thank you! Line 146: Rephrase to clarify meaning. Check word(s) omitted in sentence beginning with “During the experiment…”, specifically, “…were while…” and “…instrumentation to measure…” We cleaned up the sentence. Line 172: Check word(s) omitted in “from were”. Added. Thank you! Discussion Lines 330 – 339: Conducting further research to unravel why inconsistent results were found in the Menzies’ study is in order. However, the present authors could compare the nature of the visual scenes in the both studies to provide some possible reasons. For instance, the LAB scene may have resulted to a lesser postural instability compare to the ABS scene because it was a reconstruction of the real world. It is clear that this LAB scene is different from the visual disturbances in the Menzies’ study. We fully agree with this comment and rewrote the paragraph to elaborate on the similarity of our abstract scene and the abstract scene used by Menzies et al. and the difference to our LAB scene. We now also point out that the Menzies findings may have been much more clear when using a more realistic scene. Line 344: “(Bronstein, 1986)” should be written as “Bronstein (1986)”. Corrected. Thank you! https://doi.org/10.1371/journal.pone.0241479.r002
21 Sep 2020 Decision Letter - Eric R. Anson, Editor PONE-D-20-23613R1 Virtual reality as a tool for balance research: eyes open body sway is reproduced in photo-realistic, but not in abstract virtual scenes PLOS ONE Dear Dr. Assländer, 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. Overall the reviewer responses to the changes made were very positive. Although much improved, the paragraph "Cognitive suppression of the visual contribution" in the discussion which highlights important elements comes across as too general and disconnected from the results of the study. In your revision, please more explicitly connect this paragraph to the study results while also maintaining the broader context that is currently presented. Please submit your revised manuscript by Nov 05 2020 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: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols We look forward to receiving your revised manuscript. Kind regards, Eric R. Anson Academic Editor PLOS ONE Journal Requirements: Additional Editor Comments (if provided): [Note: HTML markup is below. Please do not edit.] 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: All comments have been addressed ******** 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 ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 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 ****** 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 ****** 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: Thank you for your revised manuscript, it is much improved. The paragraph in the discussion called “Cognitive suppression of the visual contribution” is, as said before, very interesting but needs to be in relation to the findings of your study. As it is written now, it could preferably be in the introduction. Please revise the paragraph once again to better fit in the discussion. Reviewer #2: (No Response) ****** 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: No Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0241479.r003
Revision 2
13 Oct 2020 Author Response Reviewer #1: Thank you for your revised manuscript, it is much improved. The paragraph in the discussion called “Cognitive suppression of the visual contribution” is, as said before, very interesting but needs to be in relation to the findings of your study. As it is written now, it could preferably be in the introduction. Please revise the paragraph once again to better fit in the discussion. → We are sorry for this unnecessary iteration. We were probably mentally stuck in follow-up experiments and hope we now addressed your justified criticism better. For your convenience we copied the revised paragraph below, which is the only changed section in the manuscript. Cognitive suppression of the visual contribution One striking aspect of our results is that balance in the abstract virtual scene was only slightly improved as compared to eyes closed, despite a supposedly rich visual input (large field optic flow, depth and parallax information, etc.) and using the same technical device. Above we argue that the difference to the virtual lab scene might be related to the subjective feeling of presence in the scene. However, it is unclear how a feeling of presence could affect the balance control mechanism. One mechanism could be a cognitive suppression of the visual input. It is well known that humans can suppress the visual input to standing balance. For example, Bronstein (1986) showed that subjects show a large sway response when exposed to a sudden movement of a (real world) visual surround for the first time. However, the sway response is largely suppressed during a second and succeeding exposures. The relevance of this suppression mechanism is very straight forward: subjects would fall when looking at a driving bus, if the input could not be suppressed. A similar suppression could also occur when subjects do not feel present in the scene. In other words, the feeling of presence in the virtual environment could modulate the extend to which a subject ‘trusts’ and therefore uses the visual scene as a reliable visual space reference for standing balance. Such a causal relation of presence and a cognitive suppression of the visual contribution to balance is plausible, but remains speculative at this stage. https://doi.org/10.1371/journal.pone.0241479.r004
16 Oct 2020 Decision Letter - Eric R. Anson, Editor Virtual reality as a tool for balance research: eyes open body sway is reproduced in photo-realistic, but not in abstract virtual scenes PONE-D-20-23613R2 Dear Dr. Assländer, 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. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. 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, Eric R. Anson Academic Editor PLOS ONE Additional Editor Comments (optional): 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 ******** 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 ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes ****** 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 ****** 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 ****** 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: Thank you for your revision, all my concerns are met, and the paragraph in the discussion is perfect! ****** 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:** Eva Ekvall Hansson https://doi.org/10.1371/journal.pone.0241479.r005
Formally Accepted
20 Oct 2020 Acceptance Letter - Eric R. Anson, Editor PONE-D-20-23613R2 Virtual reality as a tool for balance research: eyes open body sway is reproduced in photo-realistic, but not in abstract virtual scenes Dear Dr. Assländer: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. 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. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Eric R. Anson Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0241479.r006

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