{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,13]],"date-time":"2026-06-13T16:04:34Z","timestamp":1781366674241,"version":"3.54.1"},"reference-count":47,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2020,7,11]],"date-time":"2020-07-11T00:00:00Z","timestamp":1594425600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010661","name":"Horizon 2020 Framework Programme","doi-asserted-by":"publisher","award":["813234"],"award-info":[{"award-number":["813234"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Conventional methods for analyzing functional near-infrared spectroscopy (fNIRS) signals primarily focus on characterizing linear dynamics of the underlying metabolic processes. Nevertheless, linear analysis may underrepresent the true physiological processes that fully characterizes the complex and nonlinear metabolic activity sustaining brain function. Although there have been recent attempts to characterize nonlinearities in fNIRS signals in various experimental protocols, to our knowledge there has yet to be a study that evaluates the utility of complex characterizations of fNIRS in comparison to standard methods, such as the mean value of hemoglobin. Thus, the aim of this study was to investigate the entropy of hemoglobin concentration time series obtained from fNIRS signals and perform a comparitive analysis with standard mean hemoglobin analysis of functional activation. Publicly available data from 29 subjects performing motor imagery and mental arithmetics tasks were exploited for the purpose of this study. The experimental results show that entropy analysis on fNIRS signals may potentially uncover meaningful activation areas that enrich and complement the set identified through a traditional linear analysis.<\/jats:p>","DOI":"10.3390\/e22070761","type":"journal-article","created":{"date-parts":[[2020,7,14]],"date-time":"2020-07-14T04:46:01Z","timestamp":1594701961000},"page":"761","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["fNIRS Complexity Analysis for the Assessment of Motor Imagery and Mental Arithmetic Tasks"],"prefix":"10.3390","volume":"22","author":[{"given":"Ameer","family":"Ghouse","sequence":"first","affiliation":[{"name":"Bioengineering and Robotics Research Center E Piaggio, Universit\u00e0 di Pisa, 56123 Pisa, Italy"},{"name":"Department of Information Engineering, Universit\u00e0 di Pisa, 56123 Pisa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mimma","family":"Nardelli","sequence":"additional","affiliation":[{"name":"Bioengineering and Robotics Research Center E Piaggio, Universit\u00e0 di Pisa, 56123 Pisa, Italy"},{"name":"Department of Information Engineering, Universit\u00e0 di Pisa, 56123 Pisa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6574-1879","authenticated-orcid":false,"given":"Gaetano","family":"Valenza","sequence":"additional","affiliation":[{"name":"Bioengineering and Robotics Research Center E Piaggio, Universit\u00e0 di Pisa, 56123 Pisa, Italy"},{"name":"Department of Information Engineering, Universit\u00e0 di Pisa, 56123 Pisa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,7,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"719","DOI":"10.1006\/nimg.2002.1227","article-title":"A Quantitative Comparison of Simultaneous BOLD fMRI and NIRS Recordings during Functional Brain Activation","volume":"17","author":"Strangman","year":"2002","journal-title":"NeuroImage"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1264","DOI":"10.1126\/science.929199","article-title":"Noninvasive, infrared monitoring of cerebral and myocardial oxygen sufficiency and circulatory parameters","volume":"198","author":"Jobsis","year":"1977","journal-title":"Science"},{"key":"ref_3","first-page":"3","article-title":"fNIRS-based brain-computer interfaces: A review","volume":"9","author":"Naseer","year":"2015","journal-title":"Front. 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