Chaotic fluctuations in heart rate variability specific to mental tasks: experimental findings and a hypothesis

Chaotic fluctuations in heart rate variability specific to mental tasks: experimental findings and a hypothesis | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Chaotic fluctuations in heart rate variability specific to mental tasks: experimental findings and a hypothesis Tomoyuki Mao, Hidetoshi Okutomi, Ken Umeno This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6678475/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Mar, 2026 Read the published version in Scientific Reports → Version 1 posted 18 You are reading this latest preprint version Abstract Heart rate variability (HRV), regulated by the autonomic nervous system, is typically assessed using standard time-domain and frequency-domain methods to evaluate autonomic function. However, conventional linear analyses capture only a limited aspect of HRV, as the human body, including the cardiovascular system, is intrinsically nonlinear. In light of this, there has been growing interest in nonlinear analyses grounded in chaos theory and complexity science. In this study, we conducted a comprehensive comparison of time-domain, frequency-domain, and chaos/complexity indices derived from R–R interval (RRI) analysis during both physical and mental tasks. The results clearly demonstrate a significant increase in chaos/complexity indices during mental tasks, while conventional indices remain unchanged—underscoring the unique sensitivity of nonlinear measures to cognitive processes. These findings highlight the relevance of chaotic dynamics and complexity in HRV as a valuable perspective for understanding brain–heart interactions. Furthermore, based on the experimental findings, we propose a new hypothesis, consistent with previous research, regarding the emergence of chaotic features in HRV during cognitive activity. Biological sciences/Systems biology/Nonlinear dynamics Biological sciences/Systems biology/Time series Physical sciences/Physics/Statistical physics thermodynamics and nonlinear dynamics/Nonlinear phenomena Physical sciences/Physics/Information theory and computation Full Text Additional Declarations No competing interests reported. Supplementary Files SupplementaryInformation20250512.pdf Cite Share Download PDF Status: Published Journal Publication published 24 Mar, 2026 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 04 Aug, 2025 Reviews received at journal 02 Aug, 2025 Reviews received at journal 29 Jul, 2025 Reviews received at journal 25 Jul, 2025 Reviews received at journal 23 Jul, 2025 Reviewers agreed at journal 21 Jul, 2025 Reviewers agreed at journal 21 Jul, 2025 Reviewers agreed at journal 21 Jul, 2025 Reviewers agreed at journal 21 Jul, 2025 Reviews received at journal 05 Jun, 2025 Reviewers agreed at journal 03 Jun, 2025 Reviewers agreed at journal 03 Jun, 2025 Reviewers agreed at journal 03 Jun, 2025 Reviewers invited by journal 03 Jun, 2025 Editor assigned by journal 03 Jun, 2025 Editor invited by journal 03 Jun, 2025 Submission checks completed at journal 30 May, 2025 First submitted to journal 16 May, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6678475","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":466288188,"identity":"0f19c1dd-0736-418b-8661-467d3b222296","order_by":0,"name":"Tomoyuki Mao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDElEQVRIiWNgGAWjYPCCBB4w9QGIDZghbAbGBuxqeZC1MM5IIEELmGTmAWmBieEC9uzdiY9529JkGMQOP3xs+8PG3pyd9+AHhhobBubZ2K3h4Tm72Zi3LYeHQTrN2DgnIS1xZzNfsgTDsTQGxjkHsGuRyN0mzdtWAdSSYCadk3A4weAwj4EEY8NhiM/wa0n/Jm2RcNgeqMX4BxFaQA7LMZNmSDjMuOEwjxl+W86c3Ww451waD5t0TrFhT1pa4obDfGkWCcfSeHD5hb29d+ODN2XJ9vzS6Rsf/LCxsTc4f/bwjQ81NnKGOEIMBJhAEcGGIgR0Eo/hDJw6GBh/YBWWl8CtZRSMglEwCkYUAAB4vVNaGvCfhgAAAABJRU5ErkJggg==","orcid":"","institution":"Toshiba Information Systems (Japan) Corporation","correspondingAuthor":true,"prefix":"","firstName":"Tomoyuki","middleName":"","lastName":"Mao","suffix":""},{"id":466288193,"identity":"fbeeec76-451f-4a6d-a28e-497aaa0af266","order_by":1,"name":"Hidetoshi Okutomi","email":"","orcid":"","institution":"Toshiba Information Systems (Japan) Corporation","correspondingAuthor":false,"prefix":"","firstName":"Hidetoshi","middleName":"","lastName":"Okutomi","suffix":""},{"id":466288195,"identity":"fd7a376b-c13f-4d7f-b0a4-eaf49b60c6cb","order_by":2,"name":"Ken Umeno","email":"","orcid":"","institution":"Kyoto University","correspondingAuthor":false,"prefix":"","firstName":"Ken","middleName":"","lastName":"Umeno","suffix":""}],"badges":[],"createdAt":"2025-05-16 07:53:25","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6678475/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6678475/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-026-43385-z","type":"published","date":"2026-03-24T16:10:21+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":105754944,"identity":"e578b83c-48c2-48b7-a693-2dfd4d227861","added_by":"auto","created_at":"2026-03-30 16:23:19","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2842386,"visible":true,"origin":"","legend":"","description":"","filename":"articleMain202505163.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6678475/v1_covered_3e906e0e-6c2e-4e22-990b-854f6924c34a.pdf"},{"id":83963490,"identity":"b5286df3-aaaf-4c2f-81b5-e4ff1b50e870","added_by":"auto","created_at":"2025-06-05 06:02:29","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":908211,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation20250512.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6678475/v1/d66bc3bca12f76c3dd7bf16d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Chaotic fluctuations in heart rate variability specific to mental tasks: experimental findings and a hypothesis","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6678475/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6678475/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Heart rate variability (HRV), regulated by the autonomic nervous system, is typically assessed using standard time-domain and frequency-domain methods to evaluate autonomic function. 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