201
|
Huppert TJ. Commentary on the statistical properties of noise and its implication on general linear models in functional near-infrared spectroscopy. NEUROPHOTONICS 2016; 3:010401. [PMID: 26989756 PMCID: PMC4773699 DOI: 10.1117/1.nph.3.1.010401] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 01/22/2016] [Indexed: 05/18/2023]
Abstract
Functional near-infrared spectroscopy (fNIRS) is a noninvasive neuroimaging technique that uses low levels of light to measure changes in cerebral blood oxygenation levels. In the majority of NIRS functional brain studies, analysis of this data is based on a statistical comparison of hemodynamic levels between a baseline and task or between multiple task conditions by means of a linear regression model: the so-called general linear model. Although these methods are similar to their implementation in other fields, particularly for functional magnetic resonance imaging, the specific application of these methods in fNIRS research differs in several key ways related to the sources of noise and artifacts unique to fNIRS. In this brief communication, we discuss the application of linear regression models in fNIRS and the modifications needed to generalize these models in order to deal with structured (colored) noise due to systemic physiology and noise heteroscedasticity due to motion artifacts. The objective of this work is to present an overview of these noise properties in the context of the linear model as it applies to fNIRS data. This work is aimed at explaining these mathematical issues to the general fNIRS experimental researcher but is not intended to be a complete mathematical treatment of these concepts.
Collapse
Affiliation(s)
- Theodore J. Huppert
- University of Pittsburgh, Center for the Neural Basis of Cognition, Clinical Science Translational Institute, Departments of Radiology and Bioengineering, Pittsburgh, Pennsylvania 15260, United States
- Address all correspondence to: Theodore J. Huppert, E-mail:
| |
Collapse
|
202
|
Yamada T, Umeyama S, Ohashi M. Removal of motion artifacts originating from optode fluctuations during functional near-infrared spectroscopy measurements. BIOMEDICAL OPTICS EXPRESS 2015; 6:4632-49. [PMID: 26713183 PMCID: PMC4679243 DOI: 10.1364/boe.6.004632] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 10/21/2015] [Accepted: 10/22/2015] [Indexed: 05/24/2023]
Abstract
Functional near-infrared spectroscopy (fNIRS) has been increasingly utilized for detecting human cerebral activity in many disciplines because of the potential for less-restraining conditions. However, users often suffer from motion artifacts originating from optode fluctuation during task execution when the task includes motion. In such cases, the optode fluctuation induces changes both in the reflection by hair and in the transmission between the optode and scalp. If part of the reflected light is directly received by the detector optode (short-circuited light), it will contaminate the fNIRS signal. The transmittance change at the optode-scalp gap will also contaminate the signal. In this study, we proposed an optical model on the influence of optode fluctuation on the fNIRS signal and a method for removing the influence. The model revealed the following: (1) the received short-circuited light and the gap transmittance change generated a baseline change in the detected light intensity, and (2) the signal from the tissues was downscaled with increases in the receiving intensity of short-circuited light. To avoid erroneous detection of short-circuited light, we developed a method that optically eliminated hair-reflected light from the detection using linearly polarized light sources and an orthogonally polarized analyzer. The method was validated with an optical phantom possessing a haired surface. The optical absorbance change of a close source-detector (S-D) pair equipped with polarizers was very similar to that of distant S-D pairs, even though these optodes were artificially fluctuated. By combining the multidistance optode arrangement technique with the short-circuited light elimination method, the measurement could effectively eliminate motion artifacts originating from optode fluctuation.
Collapse
Affiliation(s)
- Toru Yamada
- Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8568,
Japan
| | - Shinji Umeyama
- Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8568,
Japan
| | | |
Collapse
|
203
|
Khan MJ, Hong KS. Passive BCI based on drowsiness detection: an fNIRS study. BIOMEDICAL OPTICS EXPRESS 2015; 6:4063-78. [PMID: 26504654 PMCID: PMC4605063 DOI: 10.1364/boe.6.004063] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 08/22/2015] [Accepted: 09/15/2015] [Indexed: 05/06/2023]
Abstract
We use functional near-infrared spectroscopy (fNIRS) to discriminate the alert and drowsy states for a passive brain-computer interface (BCI). The passive brain signals for the drowsy state are acquired from the prefrontal and dorsolateral prefrontal cortex. The experiment is performed on 13 healthy subjects using a driving simulator, and their brain activity is recorded using a continuous-wave fNIRS system. Linear discriminant analysis (LDA) is employed for training and testing, using the data from the prefrontal, left- and right-dorsolateral prefrontal regions. For classification, eight features are tested: mean oxyhemoglobin, mean deoxyhemoglobin, skewness, kurtosis, signal slope, number of peaks, sum of peaks, and signal peak, in 0~5, 0~10, and 0~15 second time windows, respectively. The results show that the best performance for classification is achieved using mean oxyhemoglobin, the signal peak, and the sum of peaks as features. The average accuracies in the right dorsolateral prefrontal cortex (83.1, 83.4 and 84.9% in the 0~5, 0~10 and 0~15 second time windows, respectively) show that the proposed method has an effective utility for detection of drowsiness for a passive BCI.
Collapse
Affiliation(s)
- M. Jawad Khan
- School of Mechanical Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 609-735, South Korea
| | - Keum-Shik Hong
- School of Mechanical Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 609-735, South Korea
- Department of Cogno-Mechatronics Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 609-735, South Korea
| |
Collapse
|
204
|
Selb J, Yücel MA, Phillip D, Schytz HW, Iversen HK, Vangel M, Ashina M, Boas DA. Effect of motion artifacts and their correction on near-infrared spectroscopy oscillation data: a study in healthy subjects and stroke patients. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:56011. [PMID: 26018790 PMCID: PMC4445402 DOI: 10.1117/1.jbo.20.5.056011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 05/04/2015] [Indexed: 05/02/2023]
Abstract
Functional near-infrared spectroscopy is prone to contamination by motion artifacts (MAs). Motion correction algorithms have previously been proposed and their respective performance compared for evoked rain activation studies. We study instead the effect of MAs on "oscillation" data which is at the basis of functional connectivity and autoregulation studies. We use as our metric of interest the interhemispheric correlation (IHC), the correlation coefficient between symmetrical time series of oxyhemoglobin oscillations. We show that increased motion content results in a decreased IHC. Using a set of motion-free data on which we add real MAs, we find that the best motion correction approach consists of discarding the segments of MAs following a careful approach to minimize the contamination due to band-pass filtering of data from "bad" segments spreading into adjacent "good" segments. Finally, we compare the IHC in a stroke group and in a healthy group that we artificially contaminated with the MA content of the stroke group, in order to avoid the confounding effect of increased motion incidence in the stroke patients. After motion correction, the IHC remains lower in the stroke group in the frequency band around 0.1 and 0.04 Hz, suggesting a physiological origin for the difference. We emphasize the importance of considering MAs as a confounding factor in oscillation-based functional near-infrared spectroscopy studies.
Collapse
Affiliation(s)
- Juliette Selb
- Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, 149 13th Street, Charlestown, Massachusetts 02129, United States
- Address all correspondence to: Juliette Selb, E-mail:
| | - Meryem A. Yücel
- Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, 149 13th Street, Charlestown, Massachusetts 02129, United States
| | - Dorte Phillip
- University of Copenhagen, Rigshospitalet, Danish Headache Center, Faculty of Health Sciences, Department of Neurology, Copenhagen, Glostrup 2600, Denmark
| | - Henrik W. Schytz
- University of Copenhagen, Rigshospitalet, Danish Headache Center, Faculty of Health Sciences, Department of Neurology, Copenhagen, Glostrup 2600, Denmark
| | - Helle K. Iversen
- University of Copenhagen, Rigshospitalet, Stroke Unit, Faculty of Health Sciences, Department of Neurology, Copenhagen, Glostrup 2600, Denmark
| | - Mark Vangel
- Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, 149 13th Street, Charlestown, Massachusetts 02129, United States
| | - Messoud Ashina
- University of Copenhagen, Rigshospitalet, Danish Headache Center, Faculty of Health Sciences, Department of Neurology, Copenhagen, Glostrup 2600, Denmark
| | - David A. Boas
- Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, 149 13th Street, Charlestown, Massachusetts 02129, United States
| |
Collapse
|
205
|
Vinette SA, Dunn JF, Slone E, Federico P. Artifact reduction in long-term monitoring of cerebral hemodynamics using near-infrared spectroscopy. NEUROPHOTONICS 2015; 2:025004. [PMID: 26158008 PMCID: PMC4478783 DOI: 10.1117/1.nph.2.2.025004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 05/01/2015] [Indexed: 05/09/2023]
Abstract
Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging technique used to assess cerebral hemodynamics. Its portability, ease of use, and relatively low operational cost lend itself well to the long-term monitoring of hemodynamic changes, such as those in epilepsy, where events are unpredictable. Long-term monitoring is associated with challenges including alterations in behaviors and motion that can result in artifacts. Five patients with epilepsy were assessed for interictal hemodynamic changes and alterations in behavior or motion. Based on this work, visual inspection was used to identify NIRS artifacts during a period of interest, specifically prior to seizures, in four patients. A motion artifact reduction algorithm (MARA, also known as the spline interpolation method) was tested on these data. Alterations in the NIRS measurements often occurred simultaneously with changes in motion and behavior. Occasionally, sharp shift artifacts were observed in the data. When artifacts appeared as sustained baseline shifts in the data, MARA reduced the standard deviation of the data and the appearance improved. We discussed motion and artifacts as challenges associated with long-term monitoring of cerebral hemodynamics in patients with epilepsy and our group's approach to circumvent these challenges and improve the quality of the data collected.
Collapse
Affiliation(s)
- Sarah A. Vinette
- University of Calgary, Faculty of Graduate Studies, Department of Neuroscience, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- Hotchkiss Brain Institute, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
| | - Jeff F. Dunn
- Hotchkiss Brain Institute, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- University of Calgary, Cumming School of Medicine, Department of Physiology and Pharmacology, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- University of Calgary, Cumming School of Medicine, Department of Radiology, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- University of Calgary, Cumming School of Medicine, Department of Clinical Neurosciences, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
| | - Edward Slone
- University of Calgary, Faculty of Graduate Studies, Department of Neuroscience, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- Hotchkiss Brain Institute, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
| | - Paolo Federico
- Hotchkiss Brain Institute, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- University of Calgary, Cumming School of Medicine, Department of Radiology, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- University of Calgary, Cumming School of Medicine, Department of Clinical Neurosciences, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
- Address all correspondence to: Paolo Federico, E-mail:
| |
Collapse
|
206
|
Hong KS, Nguyen HD. State-space models of impulse hemodynamic responses over motor, somatosensory, and visual cortices. BIOMEDICAL OPTICS EXPRESS 2014; 5:1778-98. [PMID: 24940540 PMCID: PMC4052911 DOI: 10.1364/boe.5.001778] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 05/03/2014] [Accepted: 05/03/2014] [Indexed: 05/20/2023]
Abstract
THE PAPER PRESENTS STATE SPACE MODELS OF THE HEMODYNAMIC RESPONSE (HR) OF FNIRS TO AN IMPULSE STIMULUS IN THREE BRAIN REGIONS: motor cortex (MC), somatosensory cortex (SC), and visual cortex (VC). Nineteen healthy subjects were examined. For each cortex, three impulse HRs experimentally obtained were averaged. The averaged signal was converted to a state space equation by using the subspace method. The activation peak and the undershoot peak of the oxy-hemoglobin (HbO) in MC are noticeably higher than those in SC and VC. The time-to-peaks of the HbO in three brain regions are almost the same (about 6.76 76 ± 0.2 s). The time to undershoot peak in VC is the largest among three. The HbO decreases in the early stage (~0.46 s) in MC and VC, but it is not so in SC. These findings were well described with the developed state space equations. Another advantage of the proposed method is its easy applicability in generating the expected HR to arbitrary stimuli in an online (or real-time) imaging. Experimental results are demonstrated.
Collapse
Affiliation(s)
- Keum-Shik Hong
- Department of Cogno-Mechatronics Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 609-735, South Korea
- School of Mechanical Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 609-735, South Korea
| | - Hoang-Dung Nguyen
- Department of Cogno-Mechatronics Engineering, Pusan National University; 2 Busandaehak-ro, Geumjeong-gu, Busan 609-735, South Korea
| |
Collapse
|
207
|
Scholkmann F, Metz AJ, Wolf M. Measuring tissue hemodynamics and oxygenation by continuous-wave functional near-infrared spectroscopy--how robust are the different calculation methods against movement artifacts? Physiol Meas 2014; 35:717-34. [PMID: 24622337 DOI: 10.1088/0967-3334/35/4/717] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Continuous-wave near-infrared spectroscopy and imaging enable tissue hemodynamics and oxygenation to be determined non-invasively. Movements of the investigated subject can cause movement artifacts (MAs) in the recorded signals. The strength and type of MAs induced depend on the measurement principle. The aim of the present study was to investigate the quantitative relationship between different single-distance (SD) and multi-distance (MD) measurement methods and their susceptibility to MAs. We found that each method induces MAs to a different degree, and that MD methods are more robust against MAs than SD methods.
Collapse
Affiliation(s)
- Felix Scholkmann
- Biomedical Optics Research Laboratory, Division of Neonatology, University Hospital Zurich, 8091 Zurich, Switzerland
| | | | | |
Collapse
|