{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,11]],"date-time":"2026-10-11T04:46:40Z","timestamp":1791694000550,"version":"4.3.4"},"reference-count":63,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T00:00:00Z","timestamp":1790726400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T00:00:00Z","timestamp":1790726400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China","award":["32541100"],"award-info":[{"award-number":["32541100"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"crossref"}]},{"award":["32541100"],"award-info":[{"award-number":["32541100"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Individuality, a foundational concept of traditional medicine, has been increasingly challenged by the standardization of modern healthcare. The emergence of wearable technology offers a scalable pathway toward precision health. Here, we explored the comprehensive visual representation of wearable photoplethysmography signals from a single device using the phase\u2013amplitude coupling method. We demonstrated that the coupling diagrams contain visually distinguishable regions of physiological frequency components, including those consistent with reference breathing rates (R-squared value of 0.86 for linear regression and mean absolute error of 0.017 Hz, i.e., 1.02 breaths\/min) and related to reference heart rates (R-squared value of 0.89). A similarity analysis at 0.1 Hz revealed a complex relationship between photoplethysmography signals and the derived skin sympathetic nerve activity and pulse rate variability. The numerical coupling matrices were further utilized to achieve cross-day and cross-session individual identification through machine-learning classifiers. The two-dimensional CNN classifier performed the best in the cross-session scenarios, achieving 90.37% accuracy with an equal error rate of 2.86%. This comprehensive analysis depicts the overall physiological information and individuality contained in digital pulse signals, providing conceptual and methodological foundations for future personalized health research.<\/jats:p>","DOI":"10.3390\/s26196224","type":"journal-article","created":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T15:20:59Z","timestamp":1790781659000},"page":"6224","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Individuality in Visual Representation of Pulse: A Comprehensive Analysis"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2568-8502","authenticated-orcid":false,"given":"Lu","family":"Sun","sequence":"first","affiliation":[{"name":"Department of Mathematical Sciences, Tsinghua University, Beijing 100084, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Liting","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Electronic Engineering, Tsinghua University, Beijing 100084, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"given":"Changsong","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Electronic Engineering, Tsinghua University, Beijing 100084, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"}]},{"given":"Fengshan","family":"Bai","sequence":"additional","affiliation":[{"name":"Department of Mathematical Sciences, Tsinghua University, Beijing 100084, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"given":"Zhiyi","family":"Ma","sequence":"additional","affiliation":[{"name":"School of Clinical Medicine, Tsinghua University, Beijing 100084, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"resources","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"601","DOI":"10.1007\/s40291-017-0291-y","article-title":"Are the Origins of Precision Medicine Found in the Corpus Hippocraticum?","volume":"21","author":"Konstantinidou","year":"2017","journal-title":"Mol. 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