title: Reduction of global interference of scalp-hemodynamics in functional near-infrared spectroscopy using short distance probes.
abstract: Functional near-infrared spectroscopy (fNIRS) is used to measure cerebral activity because it is simple and portable. However, scalp-hemodynamics often contaminates fNIRS signals, leading to detection of cortical activity in regions that are actually inactive. Methods for removing these artifacts using standard source-detector distance channels (Long-channel) tend to over-estimate the artifacts, while methods using additional short source-detector distance channels (Short-channel) require numerous probes to cover broad cortical areas, which leads to a high cost and prolonged experimental time. Here, we propose a new method that effectively combines the existing techniques, preserving the accuracy of estimating cerebral activity and avoiding the disadvantages inherent when applying the techniques individually. Our new method accomplishes this by estimating a global scalp-hemodynamic component from a small number of Short-channels, and removing its influence from the Long-channels using a general linear model (GLM). To demonstrate the feasibility of this method, we collected fNIRS and functional magnetic resonance imaging (fMRI) measurements during a motor task. First, we measured changes in oxygenated hemoglobin concentration (∆Oxy-Hb) from 18 Short-channels placed over motor-related areas, and confirmed that the majority of scalp-hemodynamics was globally consistent and could be estimated from as few as four Short-channels using principal component analysis. We then measured ∆Oxy-Hb from 4 Short- and 43 Long-channels. The GLM identified cerebral activity comparable to that measured separately by fMRI, even when scalp-hemodynamics exhibited substantial task-related modulation. These results suggest that combining measurements from four Short-channels with a GLM provides robust estimation of cerebral activity at a low cost.
authors.affiliation: Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan; ATR Brain Information Communication Research Lab. Group, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Sato
authors.affiliation: Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan. Electronic address: inambu@vos.nagaokaut.ac.jp.
authors.forename: Isao
authors.initials: I
authors.lastname: Nambu
authors.affiliation: ATR Brain Information Communication Research Lab. Group, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan; Fujita Memorial Nanakuri Institute, Fujita Health University, 423 Oodori-cho, Tsu, Mie 514-1296, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Takeda
authors.affiliation: ATR Neural Information Analysis Laboratories, 2-2-2 Hikaridai, Keihanna Science City, Kyoto, 619-0288, Japan.
authors.forename: Takatsugu
authors.initials: T
authors.lastname: Aihara
authors.affiliation: ATR Neural Information Analysis Laboratories, 2-2-2 Hikaridai, Keihanna Science City, Kyoto, 619-0288, Japan.
authors.forename: Okito
authors.initials: O
authors.lastname: Yamashita
authors.affiliation: ATR Brain Information Communication Research Lab. Group, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Isogaya
authors.affiliation: Research and Development Department, Medical Systems Division, Shimadzu Corporation, 1 Nishinokyo-Kuwabaracho, Nakagyo-ku, Kyoto 604-8511, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: ATR Brain Information Communication Research Lab. Group, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan; Tokyo Bay Rehabilitation Hospital, 4-1-1 Yatsu, Narashino, Chiba 275-0026, Japan; Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Otaka
authors.affiliation: Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Wada
authors.affiliation: ATR Brain Information Communication Research Lab. Group, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kawato
authors.affiliation: ATR Neural Information Analysis Laboratories, 2-2-2 Hikaridai, Keihanna Science City, Kyoto, 619-0288, Japan.
authors.forename: Masa-Aki
authors.initials: MA
authors.lastname: Sato
authors.affiliation: ATR Brain Information Communication Research Lab. Group, 2-2-2 Hikaridai, Keihanna Science City, Kyoto 619-0288, Japan. Electronic address: osu@atr.jp.
authors.forename: Rieko
authors.initials: R
authors.lastname: Osu
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D016477:Artifacts; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D015203:Reproducibility of Results; D012535:Scalp / Q000098:blood supply / Q000502:physiology*; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Functional near-infrared spectroscopy; General linear model; Multidistance probe arrangement; Principal component analysis; Scalp blood flow