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Tsytsarev V. Methodological aspects of studying the mechanisms of consciousness. Behav Brain Res 2022; 419:113684. [PMID: 34838578 DOI: 10.1016/j.bbr.2021.113684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 11/21/2021] [Accepted: 11/22/2021] [Indexed: 11/24/2022]
Abstract
There are at least two approaches to the definition of consciousness. In the first case, certain aspects of consciousness, called qualia, are considered inaccessible for research from a third person and can only be described through subjective experience. This approach is inextricably linked with the so-called "hard problem of consciousness", that is, the question of why consciousness has qualia or how any physical changes in the environment can generate subjective experience. With this approach, some aspects of consciousness, by definition, cannot be explained on the basis of external observations and, therefore, are outside the scope of scientific research. In the second case, a priori constraints do not constrain the field of scientific investigation, and the best explanation of the experience in the first person is included as a possible subject of empirical research. Historically, in the study of cause-and-effect relationships in biology, it was customary to distinguish between proximate causation and ultimate causation existing in biological systems. Immediate causes are based on the immediate influencing factors [1]. Proximate causation has evolutionary explanations. When studying biological systems themselves, such an approach is undoubtedly justified, but it often seems insufficient when studying the interaction of consciousness and the brain [2,3]. Current scientific communities proceed from the assumption that the physical substrate for the generation of consciousness is a neural network that unites various types of neurons located in various brain structures. Many neuroscientists attach a key role in this process to the cortical and thalamocortical neural networks. This question is directly related to experimental and clinical research in the field of disorder of consciousness. Progress in this area of medicine depends on advances in neuroscience in this area and is also a powerful source of empirical information. In this area of consciousness research, a large amount of experimental data has been accumulated, and in this review an attempt was made to generalize and systematize.
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2
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Fantini S, Sassaroli A. Frequency-Domain Techniques for Cerebral and Functional Near-Infrared Spectroscopy. Front Neurosci 2020; 14:300. [PMID: 32317921 PMCID: PMC7154496 DOI: 10.3389/fnins.2020.00300] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 03/16/2020] [Indexed: 12/31/2022] Open
Abstract
This article reviews the basic principles of frequency-domain near-infrared spectroscopy (FD-NIRS), which relies on intensity-modulated light sources and phase-sensitive optical detection, and its non-invasive applications to the brain. The simpler instrumentation and more straightforward data analysis of continuous-wave NIRS (CW-NIRS) accounts for the fact that almost all the current commercial instruments for cerebral NIRS have embraced the CW technique. However, FD-NIRS provides data with richer information content, which complements or exceeds the capabilities of CW-NIRS. One example is the ability of FD-NIRS to measure the absolute optical properties (absorption and reduced scattering coefficients) of tissue, and thus the absolute concentrations of oxyhemoglobin and deoxyhemoglobin in brain tissue. This article reviews the measured values of such optical properties and hemoglobin concentrations reported in the literature for animal models and for the human brain in newborns, infants, children, and adults. We also review the application of FD-NIRS to functional brain studies that focused on slower hemodynamic responses to brain activity (time scale of seconds) and faster optical signals that have been linked to neuronal activation (time scale of 100 ms). Another example of the power of FD-NIRS data is related to the different regions of sensitivity featured by intensity and phase data. We report recent developments that take advantage of this feature to maximize the sensitivity of non-invasive optical signals to brain tissue relative to more superficial extracerebral tissue (scalp, skull, etc.). We contend that this latter capability is a highly appealing quality of FD-NIRS, which complements absolute optical measurements and may result in significant advances in the field of non-invasive optical sensing of the brain.
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Affiliation(s)
- Sergio Fantini
- Department of Biomedical Engineering, Tufts University, Medford, MA, United States
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Wan N, Hancock AS, Moon TK, Gillam RB. A functional near-infrared spectroscopic investigation of speech production during reading. Hum Brain Mapp 2017; 39:1428-1437. [PMID: 29266623 DOI: 10.1002/hbm.23932] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 10/28/2017] [Accepted: 12/11/2017] [Indexed: 12/14/2022] Open
Abstract
This study was designed to test the extent to which speaking processes related to articulation and voicing influence Functional Near Infrared Spectroscopy (fNIRS) measures of cortical hemodynamics and functional connectivity. Participants read passages in three conditions (oral reading, silent mouthing, and silent reading) while undergoing fNIRS imaging. Area under the curve (AUC) analyses of the oxygenated and deoxygenated hemodynamic response function concentration values were compared for each task across five regions of interest. There were significant region main effects for both oxy and deoxy AUC analyses, and a significant region × task interaction for deoxy AUC favoring the oral reading condition over the silent reading condition for two nonmotor regions. Assessment of functional connectivity using Granger Causality revealed stronger networks between motor areas during oral reading and stronger networks between language areas during silent reading. There was no evidence that the hemodynamic flow from motor areas during oral reading compromised measures of language-related neural activity in nonmotor areas. However, speech movements had small, but measurable effects on fNIRS measures of neural connections between motor and nonmotor brain areas across the perisylvian region, even after wavelet filtering. Therefore, researchers studying speech processes with fNIRS should use wavelet filtering during preprocessing to reduce speech motion artifacts, incorporate a nonspeech communication or language control task into the research design, and conduct a connectivity analysis to adequately assess the impact of functional speech on the hemodynamic response across the perisylvian region.
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Affiliation(s)
- Nick Wan
- Department of Psychology, Utah State University, Logan, Utah, 84321
| | - Allison S Hancock
- Department of Communicative Disorders and Deaf Education, Emma Eccles Jones Early Childhood Education and Research Center, Utah State University, Logan, Utah, 84321
| | - Todd K Moon
- Department of Electrical and Computer Engineering, Utah State University, Logan, Utah, 84321
| | - Ronald B Gillam
- Department of Communicative Disorders and Deaf Education, Emma Eccles Jones Early Childhood Education and Research Center, Utah State University, Logan, Utah, 84321
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Gratton G, Chiarelli AM, Fabiani M. From brain to blood vessels and back: a noninvasive optical imaging approach. NEUROPHOTONICS 2017; 4:031208. [PMID: 28413807 PMCID: PMC5384652 DOI: 10.1117/1.nph.4.3.031208] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Accepted: 03/10/2017] [Indexed: 06/01/2023]
Abstract
The seminal work of Grinvald et al. has paved the way for the use of intrinsic optical signals measured with reflection methods for the analysis of brain function. Although this work has focused on the absorption signal associated with deoxygenation, due to its detailed mapping ability and good signal-to-noise ratio, Grinvald's group has also described other intrinsic signals related to increased blood flow, scattering effects directly related to neural activation, and pulsation effects related to arterial function. These intrinsic optical signals can also be measured using noninvasive diffuse optical topographic and tomographic imaging (DOT) methods that can be applied to humans. Here we compare the reflection and DOT methods and the evidence for each type of intrinsic signal in these two domains, with particular attention to work that has been conducted in our laboratory. This work reveals the refined two-way relationship that exists between vascular and neural phenomena in the brain: arterial health is related to normal brain structure and function, both across individuals and across brain regions within an individual, and neural function influences blood flow to specific cortical regions. DOT methods can provide quantitative tools for investigating these relationships in normal human subjects.
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Affiliation(s)
- Gabriele Gratton
- University of Illinois at Urbana Champaign, Psychology Department, Champaign, Illinois, United States
- University of Illinois at Urbana Champaign, Beckman Institute, Urbana, Illinois, United States
| | - Antonio M. Chiarelli
- University of Illinois at Urbana Champaign, Beckman Institute, Urbana, Illinois, United States
| | - Monica Fabiani
- University of Illinois at Urbana Champaign, Psychology Department, Champaign, Illinois, United States
- University of Illinois at Urbana Champaign, Beckman Institute, Urbana, Illinois, United States
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Fabiani M, Gordon BA, Maclin EL, Pearson MA, Brumback-Peltz CR, Low KA, McAuley E, Sutton BP, Kramer AF, Gratton G. Neurovascular coupling in normal aging: a combined optical, ERP and fMRI study. Neuroimage 2014; 85 Pt 1:592-607. [PMID: 23664952 PMCID: PMC3791333 DOI: 10.1016/j.neuroimage.2013.04.113] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 04/23/2013] [Accepted: 04/30/2013] [Indexed: 11/16/2022] Open
Abstract
Brain aging is characterized by changes in both hemodynamic and neuronal responses, which may be influenced by the cardiorespiratory fitness of the individual. To investigate the relationship between neuronal and hemodynamic changes, we studied the brain activity elicited by visual stimulation (checkerboard reversals at different frequencies) in younger adults and in older adults varying in physical fitness. Four functional brain measures were used to compare neuronal and hemodynamic responses obtained from BA17: two reflecting neuronal activity (the event-related optical signal, EROS, and the C1 response of the ERP), and two reflecting functional hemodynamic changes (functional magnetic resonance imaging, fMRI, and near-infrared spectroscopy, NIRS). The results indicated that both younger and older adults exhibited a quadratic relationship between neuronal and hemodynamic effects, with reduced increases of the hemodynamic response at high levels of neuronal activity. Although older adults showed reduced activation, similar neurovascular coupling functions were observed in the two age groups when fMRI and deoxy-hemoglobin measures were used. However, the coupling between oxy- and deoxy-hemoglobin changes decreased with age and increased with increasing fitness. These data indicate that departures from linearity in neurovascular coupling may be present when using hemodynamic measures to study neuronal function.
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Hwang HJ, Lim JH, Kim DW, Im CH. Evaluation of various mental task combinations for near-infrared spectroscopy-based brain-computer interfaces. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:77005. [PMID: 25036216 DOI: 10.1117/1.jbo.19.7.077005] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Accepted: 06/20/2014] [Indexed: 05/15/2023]
Abstract
A number of recent studies have demonstrated that near-infrared spectroscopy (NIRS) is a promisingneuroimaging modality for brain-computer interfaces (BCIs). So far, most NIRS-based BCI studies have focusedon enhancing the accuracy of the classification of different mental tasks. In the present study, we evaluated theperformances of a variety of mental task combinations in order to determine the mental task pairs that are bestsuited for customized NIRS-based BCIs. To this end, we recorded event-related hemodynamic responses whileseven participants performed eight different mental tasks. Classification accuracies were then estimated for allpossible pairs of the eight mental tasks (8C2 = 28). Based on this analysis, mental task combinations with relatively high classification accuracies frequently included the following three mental tasks: “mental multiplication,” “mental rotation,” and “right-hand motor imagery.” Specifically, mental task combinations consisting of two of these three mental tasks showed the highest mean classification accuracies. It is expected that our results will be a useful reference to reduce the time needed for preliminary tests when discovering individual-specific mental task combinations.
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Affiliation(s)
- Han-Jeong Hwang
- Hanyang University, Department of Biomedical Engineering, Seoul 133-791, Republic of KoreabBerlin Institute of Technology, Machine Learning Group, Marchstrasse 23, Berlin 10587, Germany
| | - Jeong-Hwan Lim
- Hanyang University, Department of Biomedical Engineering, Seoul 133-791, Republic of Korea
| | - Do-Won Kim
- Hanyang University, Department of Biomedical Engineering, Seoul 133-791, Republic of Korea
| | - Chang-Hwan Im
- Hanyang University, Department of Biomedical Engineering, Seoul 133-791, Republic of Korea
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Khan B, Hodics T, Hervey N, Kondraske G, Stowe AM, Alexandrakis G. Functional near-infrared spectroscopy maps cortical plasticity underlying altered motor performance induced by transcranial direct current stimulation. JOURNAL OF BIOMEDICAL OPTICS 2013; 18:116003. [PMID: 24193947 PMCID: PMC3817936 DOI: 10.1117/1.jbo.18.11.116003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 10/02/2013] [Indexed: 05/05/2023]
Abstract
Transcranial direct current stimulation (tDCS) of the human sensorimotor cortex during physical rehabilitation induces plasticity in the injured brain that improves motor performance. Bi-hemispheric tDCS is a noninvasive technique that modulates cortical activation by delivering weak current through a pair of anodal-cathodal (excitation-suppression) electrodes, placed on the scalp and centered over the primary motor cortex of each hemisphere. To quantify tDCS-induced plasticity during motor performance, sensorimotor cortical activity was mapped during an event-related, wrist flexion task by functional near-infrared spectroscopy (fNIRS) before, during, and after applying both possible bi-hemispheric tDCS montages in eight healthy adults. Additionally, torque applied to a lever device during isometric wrist flexion and surface electromyography measurements of major muscle group activity in both arms were acquired concurrently with fNIRS. This multiparameter approach found that hemispheric suppression contralateral to wrist flexion changed resting-state connectivity from intra-hemispheric to inter-hemispheric and increased flexion speed (p<0.05). Conversely, exciting this hemisphere increased opposing muscle output resulting in a decrease in speed but an increase in accuracy (p<0.05 for both). The findings of this work suggest that tDCS with fNIRS and concurrent multimotor measurements can provide insights into how neuroplasticity changes muscle output, which could find future use in guiding motor rehabilitation.
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Affiliation(s)
- Bilal Khan
- University of Texas at Arlington and University of Texas Southwestern Medical Center at Dallas, Joint Graduate Program in Biomedical Engineering, 500 UTA Boulevard, Arlington, Texas 76010
- Address all correspondence to: Bilal Khan, University of Texas at Arlington, Joint Graduate Program in Biomedical Engineering, 500 UTA Boulevard, Arlington, Texas 76010. Tel: +1-817-223-5518; Fax: +1-817-272-2251; E-mail:
| | - Timea Hodics
- University of Texas Southwestern Medical Center at Dallas, Department of Neurology and Neurotherapeutics, 5151 Harry Hines Boulevard, Dallas, Texas 75390
| | - Nathan Hervey
- University of Texas at Arlington and University of Texas Southwestern Medical Center at Dallas, Joint Graduate Program in Biomedical Engineering, 500 UTA Boulevard, Arlington, Texas 76010
| | - George Kondraske
- University of Texas at Arlington, Human Performance Institute, P.O. Box 19180, Arlington, Texas 76019
| | - Ann M. Stowe
- University of Texas Southwestern Medical Center at Dallas, Department of Neurology and Neurotherapeutics, 5151 Harry Hines Boulevard, Dallas, Texas 75390
| | - George Alexandrakis
- University of Texas at Arlington and University of Texas Southwestern Medical Center at Dallas, Joint Graduate Program in Biomedical Engineering, 500 UTA Boulevard, Arlington, Texas 76010
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Biallas M, Trajkovic I, Hagmann C, Scholkmann F, Jenny C, Holper L, Beck A, Wolf M. Multimodal recording of brain activity in term newborns during photic stimulation by near-infrared spectroscopy and electroencephalography. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:086011-1. [PMID: 23224198 DOI: 10.1117/1.jbo.17.8.086011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this study 14 healthy term newborns (postnatal mean age 2.1 days) underwent photic stimulation during sleep on two different days. Near-infrared spectroscopy (NIRS) and electroencephalography (EEG) was acquired simultaneously. The aims of the study were: to determine (i) the sensitivity and (ii) the repeatability of NIRS to detect the hemodynamic response, (iii) the sensitivity and (iv) the repeatability of EEG to detect a visual evoked potential (VEP), (v) to analyze optical data for the optical neuronal signal, and (vi) to test whether inadequate stimulation could be reason for absent hemodynamic responses. The results of the study were as follows. (i) Sensitivity of NIRS was 61.5% to detect hemodynamic responses; (ii) their reproducibility was 41.7%. A VEP was detected (iii) in 96.3% of all subjects with (iv) a reproducibility of 92.3%. (v) In two measurements data met the criteria for an optical neuronal signal. The noise level was 9.6·10-5% change in optical density. (vi) Insufficient stimulation was excluded as reason for absent hemodynamic responses. We conclude that NIRS is an promising tool to study cognitive activation and development of the brain. For clinical application, however, the sensitivity and reproducibility on an individual level needs to be improved.
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Affiliation(s)
- Martin Biallas
- University Hospital Zurich, Biomedical Optics Research Laboratory, Division of Neonatology, CH-8091 Zurich, Switzerland.
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Quaresima V, Bisconti S, Ferrari M. A brief review on the use of functional near-infrared spectroscopy (fNIRS) for language imaging studies in human newborns and adults. BRAIN AND LANGUAGE 2012; 121:79-89. [PMID: 21507474 DOI: 10.1016/j.bandl.2011.03.009] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 01/20/2011] [Accepted: 03/21/2011] [Indexed: 05/03/2023]
Abstract
Upon stimulation, real time maps of cortical hemodynamic responses can be obtained by non-invasive functional near-infrared spectroscopy (fNIRS) which measures changes in oxygenated and deoxygenated hemoglobin after positioning multiple sources and detectors over the human scalp. The current commercially available transportable fNIRS systems have a time resolution of 1-10 Hz, a depth sensitivity of about 1.5 cm, and a spatial resolution of about 1cm. The goal of this brief review is to report infants, children and adults fNIRS language studies. Since 1998, 60 studies have been published on cortical activation in the brain's classic language areas in children/adults as well as newborns using fNIRS instrumentations of different complexity. In addition, the basic principles of fNIRS including features, strengths, advantages, and limitations are summarized in terms that can be understood even by non specialists. Future prospects of fNIRS in the field of language processing imaging are highlighted.
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Affiliation(s)
- Valentina Quaresima
- Department of Health Sciences, University of L'Aquila, Via Vetoio, 67100 L'Aquila, Italy.
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Wallois F, Mahmoudzadeh M, Patil A, Grebe R. Usefulness of simultaneous EEG-NIRS recording in language studies. BRAIN AND LANGUAGE 2012; 121:110-23. [PMID: 21546072 DOI: 10.1016/j.bandl.2011.03.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 03/08/2011] [Accepted: 03/21/2011] [Indexed: 05/11/2023]
Abstract
One of the most challenging tasks in neuroscience in language studies, is investigation of the brain's ability to integrate and process information. This task can only be successfully addressed by applying various assessment techniques integrated into a multimodal approach. Each of these techniques has its advantages and disadvantages, but help to elucidate certain aspects of the capacity of neural networks to process information. These methods provide information about changes in electrical, hemodynamic and metabolic activities. Ideally, they should be noninvasive in order to facilitate their use particularly in children. In the present review, we describe the advantages of simultaneous electroencephalographic (EEG) acquisition with near infrared spectroscopy (NIRS) to provide a better understanding of the mechanisms involved in cerebral activation. This coregistration is also useful to avoid misleading interpretation of NIRS, notably during the various phases of sleep. Development and implementation of the various tools required and assessment strategies are also discussed.
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Affiliation(s)
- F Wallois
- GRAMFC, EA4293, Research Group on Functional Cerebral Multimodal Analysis, Faculty of Medecine, 3 rue des Louvels, 80036 Amiens, France.
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Khan B, Wildey C, Francis R, Tian F, Delgado MR, Liu H, MacFarlane D, Alexandrakis G. Improving optical contact for functional near‑infrared brain spectroscopy and imaging with brush optodes. BIOMEDICAL OPTICS EXPRESS 2012; 3:878-98. [PMID: 22567582 PMCID: PMC3342194 DOI: 10.1364/boe.3.000878] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 04/01/2012] [Accepted: 04/02/2012] [Indexed: 05/18/2023]
Abstract
A novel brush optode was designed and demonstrated to overcome poor optical contact with the scalp that can occur during functional near infrared spectroscopy (fNIRS) and imaging due to light obstruction by hair. The brush optodes were implemented as an attachment to existing commercial flat-faced (conventional) fiber bundle optodes. The goal was that the brush optodes would thread through hair and improve optical contact on subjects with dense hair. Simulations and experiments were performed to assess the magnitude of these improvements. FNIRS measurements on 17 subjects with varying hair colors (blonde, brown, and black) and hair densities (0-2.96 hairs/mm(2)) were performed during a finger tapping protocol for both flat and brush optodes. In addition to reaching a study success rate of almost 100% when using the brush optode extensions, the measurement setup times were reduced by a factor of three. Furthermore, the brush optodes enabled improvements in the activation signal-to-noise ratio (SNR) by up to a factor of ten as well as significant (p < 0.05) increases in the detected area of activation (dAoA). The measured improvements in SNR were matched by Monte Carlo (MC) simulations of photon propagation through scalp and hair. In addition, an analytical model was derived to mathematically estimate the observed light power losses due to different hair colors and hair densities. Interestingly, the derived analytical formula produced excellent estimates of the experimental data and MC simulation results despite several simplifying assumptions. The analytical model enables researchers to readily estimate the light power losses due to obstruction by hair for both flat-faced fiber bundles and individual fibers for a given subject.
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Affiliation(s)
- Bilal Khan
- Department of Bioengineering, University of Texas at Arlington, 500 UTA Boulevard, Arlington, Texas 76010, USA
| | - Chester Wildey
- MRRA Inc., 3621 Smoke Tree Trail, Euless, Texas 76040, USA
| | - Robert Francis
- Department of Electrical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | - Fenghua Tian
- Department of Bioengineering, University of Texas at Arlington, 500 UTA Boulevard, Arlington, Texas 76010, USA
| | - Mauricio R. Delgado
- Department of Neurology, Texas Scottish Rite Hospital for Children, 2222 Welborn Street, Dallas, Texas 75219, USA
- Department of Neurology, University of Texas Southwestern Medical Center at Dallas, 5901 Forest Park Road, Dallas, Texas 75390, USA
| | - Hanli Liu
- Department of Bioengineering, University of Texas at Arlington, 500 UTA Boulevard, Arlington, Texas 76010, USA
| | - Duncan MacFarlane
- Department of Electrical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | - George Alexandrakis
- Department of Bioengineering, University of Texas at Arlington, 500 UTA Boulevard, Arlington, Texas 76010, USA
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Gratton G, Fabiani M. Fast optical imaging of human brain function. Front Hum Neurosci 2010; 4:52. [PMID: 20631845 PMCID: PMC2903192 DOI: 10.3389/fnhum.2010.00052] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 06/02/2010] [Indexed: 11/29/2022] Open
Abstract
Great advancements in brain imaging during the last few decades have opened a large number of new possibilities for neuroscientists. The most dominant methodologies (electrophysiological and magnetic resonance-based methods) emphasize temporal and spatial information, respectively. However, theorizing about brain function has recently emphasized the importance of rapid (within 100 ms or so) interactions between different elements of complex neuronal networks. Fast optical imaging, and in particular the event-related optical signal (EROS, a technology that has emerged over the last 15 years) may provide descriptions of localized (to sub-cm level) brain activity with a temporal resolution of less than 100 ms. The main limitations of EROS are its limited penetration, which allows us to image cortical structures not deeper than 3 cm from the surface of the head, and its low signal-to-noise ratio. Advantages include the fact that EROS is compatible with most other imaging methods, including electrophysiological, magnetic resonance, and trans-cranial magnetic stimulation techniques, with which can be recorded concurrently. In this paper we present a summary of the research that has been conducted so far on fast optical imaging, including evidence for the possibility of recording neuronal signals with this method, the properties of the signals, and various examples of applications to the study of human cognitive neuroscience. Extant issues, controversies, and possible future developments are also discussed.
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Affiliation(s)
- Gabriele Gratton
- Department of Psychology, University of Illinois at Urbana-ChampaignUrbana, IL, USA
- Beckman Institute, University of Illinois at Urbana-ChampaignUrbana, IL, USA
| | - Monica Fabiani
- Department of Psychology, University of Illinois at Urbana-ChampaignUrbana, IL, USA
- Beckman Institute, University of Illinois at Urbana-ChampaignUrbana, IL, USA
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Fantini S, Chen DK, Martin JM, Sassaroli A, Bergethon PR. Near-infrared signals associated with electrical stimulation of peripheral nerves. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2009; 7174:71741C. [PMID: 22399834 PMCID: PMC3293485 DOI: 10.1117/12.809428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
We report our studies on the optical signals measured non-invasively on electrically stimulated peripheral nerves. The stimulation consists of the delivery of 0.1 ms current pulses, below the threshold for triggering any visible motion, to a peripheral nerve in human subjects (we have studied the sural nerve and the median nerve). In response to electrical stimulation, we observe an optical signal that peaks at about 100 ms post-stimulus, on a much longer time scale than the few milliseconds duration of the electrical response, or sensory nerve action potential (SNAP). While the 100 ms optical signal we measured is not a direct optical signature of neural activation, it is nevertheless indicative of a mediated response to neural activation. We argue that this may provide information useful for understanding the origin of the fast optical signal (also on a 100 ms time scale) that has been measured non-invasively in the brain in response to cerebral activation. Furthermore, the optical response to peripheral nerve activation may be developed into a diagnostic tool for peripheral neuropathies, as suggested by the delayed optical signals (average peak time: 230 ms) measured in patients with diabetic neuropathy with respect to normal subjects (average peak time: 160 ms).
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Affiliation(s)
- Sergio Fantini
- Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155
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