{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,10]],"date-time":"2026-01-10T21:33:17Z","timestamp":1768080797039,"version":"3.49.0"},"reference-count":37,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2019,2,27]],"date-time":"2019-02-27T00:00:00Z","timestamp":1551225600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004837","name":"Ministerio de Ciencia e Innovaci\u00f3n","doi-asserted-by":"publisher","award":["DPI2017-84280-R"],"award-info":[{"award-number":["DPI2017-84280-R"]}],"id":[{"id":"10.13039\/501100004837","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100008530","name":"European Regional Development Fund","doi-asserted-by":"publisher","award":["DPI2017-84280-R"],"award-info":[{"award-number":["DPI2017-84280-R"]}],"id":[{"id":"10.13039\/501100008530","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100013276","name":"Interreg","doi-asserted-by":"publisher","award":["An\u00e1lisis y correlaci\u00f3n entre el genoma completo y la actividad cerebral para la ayuda en el diagn\u00f3stico de la enfermedad de Alzheimer"],"award-info":[{"award-number":["An\u00e1lisis y correlaci\u00f3n entre el genoma completo y la actividad cerebral para la ayuda en el diagn\u00f3stico de la enfermedad de Alzheimer"]}],"id":[{"id":"10.13039\/100013276","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.mdpi.com"],"crossmark-restriction":true},"short-container-title":["Entropy"],"abstract":"<jats:p>Brain\u2013computer interfaces (BCI) have traditionally worked using synchronous paradigms. In recent years, much effort has been put into reaching asynchronous management, providing users with the ability to decide when a command should be selected. However, to the best of our knowledge, entropy metrics have not yet been explored. The present study has a twofold purpose: (i) to characterize both control and non-control states by examining the regularity of electroencephalography (EEG) signals; and (ii) to assess the efficacy of a scaled version of the sample entropy algorithm to provide asynchronous control for BCI systems. Ten healthy subjects participated in the study, who were asked to spell words through a visual oddball-based paradigm, attending (i.e., control) and ignoring (i.e., non-control) the stimuli. An optimization stage was performed for determining a common combination of hyperparameters for all subjects. Afterwards, these values were used to discern between both states using a linear classifier. Results show that control signals are more complex and irregular than non-control ones, reaching an average accuracy of     94 . 40 %     in classification. In conclusion, the present study demonstrates that the proposed framework is useful in monitoring the attention of a user, and granting the asynchrony of the BCI system.<\/jats:p>","DOI":"10.3390\/e21030230","type":"journal-article","created":{"date-parts":[[2019,2,27]],"date-time":"2019-02-27T11:41:03Z","timestamp":1551267663000},"page":"230","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["Asynchronous Control of P300-Based Brain\u2013Computer Interfaces Using Sample Entropy"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3822-1787","authenticated-orcid":false,"given":"V\u00edctor","family":"Mart\u00ednez-Cagigal","sequence":"first","affiliation":[{"name":"Biomedical Engineering Group, E.T.S.I. Telecomunicaci\u00f3n, University of Valladolid, Paseo de Bel\u00e9n 15, 47011 Valladolid, Spain"}]},{"given":"Eduardo","family":"Santamar\u00eda-V\u00e1zquez","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Group, E.T.S.I. Telecomunicaci\u00f3n, University of Valladolid, Paseo de Bel\u00e9n 15, 47011 Valladolid, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9915-2570","authenticated-orcid":false,"given":"Roberto","family":"Hornero","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Group, E.T.S.I. Telecomunicaci\u00f3n, University of Valladolid, Paseo de Bel\u00e9n 15, 47011 Valladolid, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2019,2,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Wolpaw, J.R., and Wolpaw, E.W. (2012). 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