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Simultaneous Recording of Cerebral Blood Oxygenation Changes During Human Brain Activation by Magnetic Resonance Imaging and Near-Infrared Spectroscopy
Abstract
Changes in cerebral blood oxygenation due to functional activation of the primary sensorimotor cortex during a unilateral finger opposition task were simultaneously mapped by deoxyhemoglobin-sensitive magnetic resonance imaging (MRI) and monitored by near-infrared spectroscopy (NIRS). Activation foci along the contralateral central sulcus displayed task-associated increases in MRI signal intensity, indicating a concomitant decrease of the focal concentration of deoxyhemoglobin. This interpretation was confirmed by simultaneous reductions in deoxyhemoglobin measured optically. Since observation of the latter effect required exact spatial matching of the MRI-detected activation foci and position of the fiber optic bundles ("optodes") used for transmitting and receiving light, it may be concluded that optical recordings of changes in deoxyhemoglobin during functional challenge probe only a restricted brain tissue region. While deoxyhemoglobin responses seen by NIRS were smaller for ipsi- than for contralateral finger movements, task-related increases in oxyhemoglobin were rather similar between both conditions and, thus, seem to be less specific. Furthermore, no consistent changes were obtained for total hemoglobin during task performance, possibly due to the short timing of the repetitive protocol. In general, results underline, in humans, the hitherto assumed signal physiology for functional brain mapping by oxygenation-sensitive MRI and allow assessment of both constraints and practicability of functional studies by NIRS.
... Several studies investigated the fNIRS/fMRI correspondence, both simultaneously (Anwar et al., 2016;Cui et al., 2011;Huppert et al., 2017a;Huppert et al., 2006;Kleinschmidt et al., 1996;Mehagnoul--Schipper et al., 2002;Sato et al., 2013;Strangman et al., 2002;Toronov et al., 2003;Toronov et al., 2001;Wijeakumar et al., 2017) or separately (Klein et al., 2022;Noah et al., 2015) (Cai et al., 2021) (Wagner et al., 2021) (Maggioni et al., 2015), during the execution of tasks. For instance, Toronov et al. (Toronov et al., 2001) qualitatively studied both temporal and spatial signal correspondence, showing a good temporal correlation between fNIRS and fMRI signals located in the expected motor areas. ...
... Specifically, with spatial agreement, we refer to the correspondence of statistically significant functional activation as alternatively seen by fMRI or fNIRS according to corresponding anatomical areas and/or regions of interest (ROIs). Spatial agreement in the current fNIRS-fMRI literature has mostly assessed the correspondence between fNIRS source and detector positions with respect to cortical areas from anatomical MRI (Kleinschmidt et al., 1996;Mehagnoul-Schipper et al., 2002;Strangman et al., 2002;Toronov et al., 2003;Toronov et al., 2001). As a result, both fMRI and fNIRS signals are averaged through heterogeneous methods to define a common analysis space, thus possibly affecting the reproducibility of results if employing a different fNIRS probe configuration. ...
... The proposed surface-based approach allowed for the definition of ROIs for directly comparing fNIRS and fMRI over common statistically significant cortical areas instead of only considering optodes positioning. Indeed, most of the early fNIRS-fMRI studies established a spatial correspondence between anatomical MRI and fNIRS optode positioning (Kleinschmidt et al., 1996;Mehagnoul-Schipper et al., 2002;Strangman et al., 2002;Toronov et al., 2003;Toronov et al., 2001). Notably, Strangman et al. (Strangman et al., 2002) were also the first to propose that fNIRS-fMRI spatial correspondence must consider the segmentation of anatomical MRI for providing fNIRS source reconstruction in a 3D space. ...
Introduction:
Studies integrating functional near-infrared spectroscopy (fNIRS) with functional MRI (fMRI) employ heterogeneous methods in defining common regions of interest in which similarities are assessed. Therefore, spatial agreement and temporal correlation may not be reproducible across studies. In the present work, we address this issue by proposing a novel method for integration and analysis of fNIRS and fMRI over the cortical surface.
Materials and methods:
Eighteen healthy volunteers (age mean±SD 30.55±4.7, 7 males) performed a motor task during non-simultaneous fMRI and fNIRS acquisitions. First, fNIRS and fMRI data were integrated by projecting subject- and group-level source maps over the cortical surface mesh to define anatomically constrained functional ROIs (acfROI). Next, spatial agreement and temporal correlation were quantified as Dice Coefficient (DC) and Pearson's correlation coefficient between fNIRS-fMRI in the acfROIs.
Results:
Subject-level results revealed moderate to substantial spatial agreement (DC range 0.43 - 0.64), confirmed at the group-level only for blood oxygenation level-dependent (BOLD) signal vs. HbO2 (0.44 - 0.69), while lack of agreement was found for BOLD vs. HbR in some instances (0.05 - 0.49). Subject-level temporal correlation was moderate to strong (0.79 - 0.85 for BOLD vs. HbO2 and -0.62 - -0.72 for BOLD vs. HbR), while an overall strong correlation was found for group-level results (0.95 - 0.98 for BOLD vs. HbO2 and -0.91 - -0.94 for BOLD vs. HbR).
Conclusion:
The proposed method directly compares fNIRS and fMRI by projecting individual source maps to the cortical surface. Our results indicate spatial and temporal correspondence between fNIRS and fMRI, and promotes the use of fNIRS when more ecological acquision settings are required, such as longitudinal monitoring of brain activity.
... Twenty healthy, right-handed individuals (6 males, 14 females; mean (SD) age 30.9 (4.9) years, range [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] with no history of neurological, physical, or psychiatric illness were recruited for this study. Four additional individuals were initially recruited, but their data could not be analyzed owing to the poor quality of the fNIRS signal. ...
... However, few studies have found strong correlations between HbR concentration and fMRI BOLD signals. HbO 2 concentration seems to be more sensitive to brain activation than HbR (Kleinschmidt et al. 1996 ...
Characterization of cortical activation patterns during movements in healthy adults may help our understanding of how the injured brain works. Upper limb motor tasks are commonly used to assess impaired motor function and to predict recovery in individuals with neurological disorders such as stroke. This study aimed to explore cortical activation patterns associated with movements of the hand and shoulder using functional near-infrared spectroscopy (fNIRS).
Twenty healthy, right-handed participants were recruited. Two 10-s motor tasks (right-hand opening-closing and right shoulder abduction-adduction) were performed in a sitting position at a rate of 0.5 Hz in a block paradigm. We measured the variations in oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR) concentrations. fNIRS was performed with a 24-channel system (Brite 24®; Artinis) that covered most motor control brain regions bilaterally.
Activation was mostly contralateral for both hand and shoulder movements. Activation was more lateral for hand movements and more medial for shoulder movements, as predicted by the classical homunculus representation. We also found ipsilateral activation for both tasks. Both HbO2 and HbR concentrations varied with the activity.
Our data confirm that unilateral movements require bilateral activation of the sensorimotor cortex with stronger activation of the contralateral cortex. We also showed that fNIRS can distinguish patterns of cortical activity in upper limb movements under ecological conditions. These results suggest that fNIRS could be used to measure spontaneous motor recovery and rehabilitation-induced recovery after brain injury.
The trial was restropectively registered on January 20, 2023: NCT05691777 (clinicaltrial.gov)
... Functional near-infrared spectroscopy (fNIRS) is a noninvasive tool for recording hemodynamic activity along the scalp time-locked to response events. By measuring the absorption of the near-infrared light (650-950 nm) through the scalp (Villringer & Chance, 1997;Villringer & Dirnagl, 1994), fNIRS can detect hemodynamic changes in the concentration of oxyhemoglobin and deoxy-hemoglobin in brain regions (Ferrari, Mottola, & Quaresima, 2004;Jobsis, 1977;Kleinschmidt et al., 1996;Strangman, Boas, & Sutton, 2002a;Strangman, Culver, Thompson, & Boas, 2002b;Villringer, Planck, Hock, Schleinkofer, & Dirnagl, 1993). Previous studies suggest that fNIRS data are highly consistent with data from the most widely used neuroimaging modality, functional magnetic resonance imaging (fMRI) (Strangman, Boas, et al., 2002a;Strangman, Culver, et al., 2002b), but fNIRS further provides many advantages over other neuroimaging tools. ...
... In fNIRS statistical analysis, the most common approach is to average signals across all time points of the event of interest, but this technique is limited by loss of time course information. Statistical methods such as the t test or analysis of variance (ANOVA) would then be applied on these averaged values in order to draw a conclusion (Germon et al., 1999;Hoshi, 2003;Hoshi, Kobayashi, & Tamura, 2001;Isobe et al., 2001;Kleinschmidt et al., 1996;Mehagnoul-Schipper et al., 2002;Okamoto et al., 2004). However, this averaging approach is not sensitive for detecting temporal information of brain activation related to mental activity (Tak & Ye, 2014). ...
In the data analysis of functional near-infrared spectroscopy (fNIRS), linear model frameworks, in particular mass univariate analysis, are often used when researchers consider examining the difference between conditions at each sampled time point. However, some statistical issues, such as assumptions of linearity, autocorrelation and multiple comparison problems, influence statistical inferences when mass univariate analysis is used on fNIRS time course data. In order to address these issues, the present study proposes a novel perspective, multi-time-point analysis (MTPA), to discriminate signal differences between conditions by combining temporal information from multiple time points in fNIRS. In addition, MTPA adopts the random forest algorithm from the statistical learning domain, followed by a series of cross-validation procedures, providing reasonable power for detecting significant time points and ensuring generalizability. Using a real fNIRS data set, the proposed MTPA outperformed mass univariate analysis in detecting more time points, showing significant differences between experimental conditions. Finally, MTPA was also able to make comparisons between different areas, leading to a novel viewpoint of fNIRS time course analysis and providing additional theoretical implications for future fNIRS studies. The data set and all source code are available for researchers to replicate the analyses and to adapt the program for their own needs in future fNIRS studies.
... Moreover, although fNIRS has lower spatial resolution compared to fMRI, fNIRS devices are more convenient and suitable for mobile scenarios [13]. In comparison to EEG, fNIRS shows an advantage of the higher spatial resolution. ...
Brain-computer interface (BCI) based on motor imagery (MI) and mental arithmetic (MA) is an emerging technique with significant potential for assisting disabled individuals. Functional near-infrared spectroscopy (fNIRS) plays a crucial role in enhancing the performance of BCI systems due to its relatively high spatial resolution. However, the accuracy of BCI systems using fNIRS still needs improvement. In this study, we focused on the characteristics of fNIRS and used large-kernel dilation convolution to extract the hemodynamic features of the brain from fNIRS data. Inspired by the application of CapsuleNet in image classification, we designed an improved dilation CapsuleNet (ID-CapsuleNet), which combines large-kernel dilation convolution and CapsuleNet. To evaluate the performance of the proposed model, we utilized four publicly available datasets A, B, C and D. The former two datasets are MA type while the latter two datasets are MI type. The results demonstrated that the average accuracies for each dataset reached 95.01%, 76.88%, 74.03%, and 80.29%, and the cross-subject average accuracies reached 88.72%, 75.80%, 75.78%, and 80.34%, respectively. Moreover, we conducted ablation experiments and demonstrated the usefulness and importance of the large-kernel convolution, dynamic routing, and dilation convolution for the proposed model.
... This condition is related to neuronal activity at the cortical capillary level over the scalp and can be measured with fNIRS and NIRS (4,5). fNIRS is an effective and reliable imaging method for examining the relationship between hemodynamic changes and neural activity, providing consistent and parallel results with other hemodynamic imaging techniques such as fMRI and positron emission tomography (PET) (5,6). Research with the fNIRS method has expanded rapidly as the fNIRS system has some advantages (compared to fMRI), such as relatively high temporal In the last decade, with the development of its technology, the fNIRS method was used by multiple disciplines in various experimental designs to investigate cognitive functions as well as sensory systems under different conditions (4,9). ...
Olfaction is critical for maintaining daily life activities. It is crucial to measure olfactory performance for the diagnosis and treatment of certain neurodegenerative diseases. Moreover, impairments and a lack of quality in the olfactory system may indicate the early diagnosis of some diseases such as Parkinson’s. In this context, there are several imaging methods available for evaluating olfactory function. In addition to the conventional methods used in measuring the brain's responsiveness to olfactory stimuli, this article presents a systematic review of the current applicability of optical brain imaging (i.e., functional near-infrared spectroscopy) in the evaluation of olfactory function. A database literature search was conducted in PubMed, Scopus, the Web of Science, and ScienceDirect. This review excluded animal studies, clinical studies, pathology- or neurodegenerative disease-related studies, newborn-related studies, cross-modal- and dual-task-related studies, and non-original research studies. Thus, seven studies were examined to discuss the pitfalls and perspectives of the use of optical brain imaging under olfactory stimulation. As for this conclusion, they can be used to evaluate olfactory performance in healthy individuals through the interpretation of hemodynamic changes. Further studies are needed to standardize the applicability of these optical imaging techniques.
... 10 fNIRS can measure changes in oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) that correlate with the metabolic activity of neurons, similar to the blood oxygen level-dependent response obtained by fMRI. 11,12 fNIRS is a promising method for investigating the relationship between interpersonal interactions in natural settings and their neural activities, and it has advantages of cost-effectiveness, low constraints on measurements, and relatively high tolerance to head and body motion. 13,14 Recently researchers could better measure the inter-brain coupling associated with social interactions, and many studies about educational communication, a face-to-face game, improving cognitive performance, and body physiology between subjects have been reported using the fNIRS-based hyperscanning technology. ...
Significance:
We developed a MATLAB-based toolbox for the analysis of inter-brain synchrony (IBS) and performed an experimental study to confirm its performance. To the best of our knowledge, this is the first toolbox for IBS based on functional near-infrared spectroscopy (fNIRS) hyperscanning data that visually shows the results on two three-dimensional (3D) head models.
Aim:
Research on IBS using fNIRS hyperscanning is a nascent but expanding field. Although various analysis toolboxes for fNIRS exist, none can show inter-brain neuronal synchrony on a 3D head model. In 2019 and 2020, we released two MATLAB toolboxes named OptoNet I and II, which have helped researchers to analyze functional brain networks using fNIRS. We developed a MATLAB-based toolbox named HyperOptoNet to overcome the limitation of the previous OptoNet series.
Approach:
The developed HyperOptoNet can easily analyze inter-brain cortical connectivity using fNIRS hyperscanning signals simultaneously measured from two people at the same time. The connectivity results can be easily recognized by representing inter-brain neuronal synchrony with colored lines that are visually expressed on two standard head models.
Results:
To evaluate the performance of the developed toolbox, we conducted an fNIRS hyperscanning study of 32 healthy adults. The fNIRS hyperscanning data were measured while the subjects performed traditional, paper-and-pencil-based, cognitive tasks or interactive, computer-assisted, cognitive tasks (ICT). The results visualized different inter-brain synchronization patterns according to the interactive nature of the given tasks; a more extensive inter-brain network was seen with the ICT.
Conclusions:
The developed toolbox has good performance of IBS analysis and helps even unskilled researchers to easily analyze fNIRS hyperscanning data.
... À l'égard de telles divergences de résultats, les chercheurs ont comparé les signaux fNIRS avec d'autres modalités d'imagerie afin d'obtenir des informations plus instructives. Des études ont démontré que les réponses d'HbR semblent être plus localisées et topographiquement plus proches des aires activées (Kleinschmidt et al., 1996 ;Kaiser et al., 2014) que les changements d'HbO (Obrig and Villringer, 2003 ;Bauernfeind et al., 2014) . Cependant, les changements d'HbR présentent un rapport signal/bruit plus faible (Strangman et al., 2002 ;Huppert et al., 2006) et ont une origine moins corticale que l'HbO (Gagnon et al., 2012) . ...
Introduction La surdité unilatérale est une pathologie fréquente chez l'enfant. Les répercussions en sont importantes tant sur le plan de l'audition spatiale que sur l'aspect du développement psychosocial. À ce jour, très peu de données neurofonctionnelles ont été recueillies chez l'enfant. L'objectif de cette thèse est donc d'étudier, chez l'enfant, le lien entre l'atteinte auditive unilatérale et ses corrélats neuraux. Cet objectif repose sur deux études, lesquelles sont définies comme suit : 1) Procéder à l'identification des paramètres de stimulation optimaux utilisés en fNIRS afin d'obtenir un signal de qualité sur l'enfant et, 2) Mesurer la réorganisation corticale suite à la surdité unilatérale et corréler cette réorganisation aux performances psychoacoustiques, psychosociales. Matériels et méthodes S'agissant de la première étude, dix-sept sujets adultes normo-entendants ont été recrutés. Ils ont été soumis à quatre conditions de stimulation auditive en fNIRS. L'amplitude du signal fNIRS enregistré et la durée expérimentale ont été comparées, entre ces conditions. Concernant la seconde étude, quatre enfants porteurs de surdité unilatérale ont été inclus. Ils ont été évalués en psychoacoustique par les tests de localisation du son dans l'espace et de la compréhension de la parole dans le bruit, en neurofonctionnel par la fNIRS, et en développement psychosocial par les tests mesurant les habiletés linguistiques différentes. Ils ont enfin répondu aux questionnaires de qualité de vie. Résultats L'étude 1 a identifié la durée de stimulation de 15 s comme étant un choix optimal, lorsqu'elle est associée à une amplitude trois fois plus importante et à une durée plus courte de 105 s que les autres conditions de stimulation. L'étude 2 a démontré une grande variabilité des résultats en performances psychoacoustiques et psychosociales. De plus, la surdité unilatérale a induit une augmentation de l'activation corticale ipsilatérale à l'oreille saine. Cette augmentation est significativement corrélée aux performances binaurales. Conclusion La surdité unilatérale induit des phénomènes de réorganisation corticale associés à une forte variabilité des performances binaurales et psychosociales, suggérant l'existence de facteurs compensatoires. Ce travail souligne la nécessité de l'identification de ces facteurs compensatoires et d'une prise en charge des enfants vulnérables aux effets néfastes de la surdité unilatérale.
... Partial volume effect (i.e., when sampling from activated and non-activated tissues) is another possible explanation for the observed response (Boas et al., 2001;Kleinschmidt et al., 1996;Strangman, Culver, Thompson, & Boas, 2002), but that is impossible to assess in one-modality studies. Systemic perfusion noise has also been attributed to inverse fNIRS responses (Caldwell et al., 2016), which is unlikely in our study due to short-separation regression. ...
Background:
Following acute ischemic stroke (AIS) many patients experience cognitive impairment which interferes neurorehabilitation. Understanding and monitoring pathophysiologic processes behind cognitive symptoms requires accessible methods during testing and training. Functional near-infrared spectroscopy (fNIRS) can assess activational hemodynamic responses in the prefrontal cortex (PFC) and feasibly be used as a biomarker to support stroke rehabilitation.
Objective:
Exploring the feasibility of fNIRS as a biomarker during the Stroop Color and Word Test (SCWT) assessing executive function in AIS patients.
Methods:
Observational study of 21 patients with mild to moderate AIS and 22 healthy age- and sex-matched controls (HC) examined with fNIRS of PFC during the SCWT. Hemodynamic responses were analyzed with general linear modeling.
Results:
The SCWT was performed worse by AIS patients than HC. Neither patients nor HC showed PFC activation, but an inverse activational pattern primarily in superolateral and superomedial PFC significantly lower in AIS. Hemodynamic responses were incoherent to test difficulty and performance. No other group differences or lateralization were found.
Conclusions:
AIS patients had impaired executive function assessed by the SCWT, while both groups showed an inverse hemodynamic response significantly larger in HC. Investigations assessing the physiology behind inverse hemodynamic responses are warranted before deeming clinical implementation reasonable.
... In light of the absorption spectra, differences between oxyhemoglobin (HbO) and deoxyhemoglobin (HbR), the concentration changes of these two measures can be examined from diffusely scattered light sources (Ferrari et al., 2004;Jobsis, 1977;Kleinschmidt et al., 1996). Fantini and Sassaroli (2020) stated that the estimated measurements for the HbO and HbR could be extracted when the Modified Beer-Lambert Law (MBLL) is applied to the data obtained from the light within the near-infrared range of the electromagnetic spectrum and can be absorbed by hemoglobin. ...
Functional near-infrared spectroscopy (fNIRS) signals are used to measure relative changes in oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) concentrations. Brain response studies constitute multilevel or nested datasets formed by different parts of the brain of individuals and multidimensional datasets. The changes in brain activities under specific stimuli are investigated with the help of statistical analysis. However, these studies ignore the dependence structure between the repeated measures of the same subject, which may cause inaccurate or incomplete findings. In this study, we adopt an advanced statistical method into HbO data controlling for variability within repeated measures of each subject while testing and measuring the degrees of the statistical significance between-subject factors and explanatory variables. The changes in HbO are investigated through a linear mixed model, taking experimental and demographic variables into account with open access neuroscience data. The channels nested within subjects are considered random to capture the differences among individuals. Our findings reveal that n-back conditions and mean response times of the subjects have statistically significant associations with mean HbO.
... The excitability of contralateral M1 of the trained hand significantly increased with increased task complexity [29,34]. In addition, there is evidence that the premotor motor area, auxiliary motor area, and attentional cognition area are also involved in the learning of complex sequential motor tasks [26][27][28][35][36][37][38]. ...
Purpose:
Task complexity could affect acquisition efficiency of motor skills and interlimb transfer; however, how task complexity affects interlimb transfer remains unclear. We hypothesized that left- and right-handed participants may have different interlimb transfer efficiency depending on the task complexity.
Methods:
Left-hand (n=28) and right-hand (n=28) dominant participants (age=24.70 ± 4.02 years, male:female=28:28) performed a finger sequence test with two levels of complexity (simple: one-digit with four fingers vs. complex: two-digit with five fingers) before and after ten trials of 2-min practice each on the same apparatus. The speed and task errors were measured and analyzed.
Results:
Right-handed participants failed to improve performance on their right hand (non-trained hand) after contralateral left-hand practice in the simple finger sequence task. In contrast, the left-handed participants improved performance on non-trained hands both right and left after contralateral practices. In the complex task, however, both the left- and right-handed participants improved performance on non-trained hands by contralateral practices.
Conclusion:
Our results showed that task complexity of skilled practice gave different effects on interlimb transfer between right- and left-handed subjects. It appears that a certain level of appropriate complexity is necessary to detect inter-limb transfers in motor learning in right-handed subjects.
... As the increase in rCBF exceeds the increase in rCMRO2, this results in a decrease in the HbR in venous blood and increases in HbO (Fig .9). Several studies (Hoshi and Tamura, 1993;Kato et al., 1993;Kleinschmidt et al., 1996) have shown either an absence of HbT variation with an increase in HbO/decrease in HbR, or an increase/absence of HbR accompanying HbT and HbO increases. Besides, the initial dip may correspond to an increase in HbR due to a mismatch between CMRO2 and CBF (Kim and Kim, 2011), or increases in CBV (Buxton et al., 1998). ...
Neurovascular coupling (NVC) has become the key aspect for understanding brain function. A multimodal exploration would aim to identify the early NVC biomarkers and determine their predictive character. Paper (1): In this chapter, the photothermal interaction of NIR laser on human tissues were modelled in silico. The results demonstrated the safety of the noninvasive optical evaluation of the brain function and the maximum temperature increase was higher in the neonatal brain than in the adult brain. Paper (2 & 3): The main purpose of this thesis was to provide a multimodal view of the NVC and cerebrovascular regulation in the neonatal premature brain. Paper (2): Key findings included that rCBV and rCMRO2 have a predominant driving influence on rCBF at the resting-state in the preterm neonatal brain. Paper (3): The bursts of electroencephalographic activity in neonates in resting state were found to be coupled to a transient hemodynamic response involving different types of hemodynamic response including: (a) positive stereotyped hemodynamic responses (increases in HbO, decreases in HbR together with increases in CBF and CMRO2), (b) negative hemodynamic responses (increases in HbR, decreases in HbO together with decreases in CBF and CMRO2), (c) Increases and decreases in both HbO-HbR and CMRO2 together with no changes in CBF. The establishment of neurovascular coupling system was observed as a function of age. High coherence was observed between the cerebral hemodynamic (vascular) and electrical (neuronal) oscillations which was less in the non-encephalopathic newborns than in the two pathological groups
... The measurements of oxyhaemoglobin ( [HbO 2 ]) and deoxyhaemoglobin ( [HHb]) concentrations were done using an 85 × 20 mm transcranial probe, applied 2 cm above the root of the nose and connected with a near-infrared spectroscope (NIRS, Nirox S.r.l) just above the supraorbital ridge (Kleinschmidt et al., 1996). Based on the transparency principle of human tissue to the near-infrared radiation, it uses light in the spectrum from 650 to 1,000 nm. ...
Purpose: Investigate the feasibility of a non-invasive method to evaluate the physical and cognitive repercussions of long-lasting post-concussion effects in professional combat sports athletes. To help athletes return to professional combat, there is a need for unbiased objective tools and techniques used as a prognostic method of recovery after Sport Related Concussion (SRC).
Methods: Six mild Traumatic Brain Injury (mTBI) athletes, age 20 ÷ 43 yr (1 female, 5 males) and 7 not concussed (NC) participants (amateur), age 24 ÷ 38 yr (3 females, 4 males), were tested Inspired/expired gas concentration, Cerebral changes in oxygenated hemoglobin (Δ[HbO 2 ]) and deoxygenated hemoglobin (Δ[HHb]) were measured using near infrared spectroscopy (NIRS) with a 3-step protocol: rest before maximal oxygen uptake (VO 2 max) test, hypercapnia, and recovery after VO 2 max test. The brain oxygenation and respiratory parameters of both sample sets were calculated using a non-parametric test (Mann-Whitney U test). Aerobic fitness outcome was quantified through mean average using the Bruce test. Participants performed Fitt's test using a laptop and analysis of medio-lateral and anterior-posterior range of oscillation was carried out via a force platform Romberg test.
Results: mTBI group showed statistically significant differences in saturated hemoglobin Δ[HbO 2 ] ( p < 0.001) during rest and recovery phase after maximal incremental exercise, in medio-lateral sway eyes open ( p = 0.008, NC 25.35 ± 4.11 mm and mTBI 17.65 ± 4.79 mm). VO 2 max revealed no significant differences between the two groups: NC 47.47 ± 4.91 mTBI 49.58 ± 5.19 ml/kg/min ⁻¹ . The 2 groups didn't differ for maximum power output (NC 220 ± 34, mTBI 255 ± 50 W). End-tidal fractional concentration of O 2 (FetO 2 NC15.20 ± 0.41, mTBI 16.09 ± 0.68) throughout hypercapnia, saturated blood hemoglobin (Δ[HbO 2 ]) revealed significant differences with the mTBI group. No differences emerged from Fitt's test.
Conclusions: It emerges that NIRS is able to reveal differences in long time outcomes of mTBI. The medio-lateral variations cannot be considered as a marker of long-term damage in athletes specifically trained for balance.
... In the presence of deoxy-Hb in the blood, a small fluctuation of hematocrit alone can directly affect the fMRI signal (Dent et al., 2016). Axial variation of hematocrit in the vessels has been theoretically suggested in relation to both neurovascular coupling (Chen & Pike, 2009;Kleinschmidt et al., 1996;Siegel et al., 2003) and sLFOs (Fagrell et al., 1980;Mayhew et al., 1996). Vasomotion drives local velocity fluctuations, termed "flowmotion" (Intaglietta, 1990), which reportedly accompany local hematocrit fluctuation (Fagrell et al., 1980;Hudetz et al., 1999). ...
Possible formation of G-quadruplex (G4G-quadruplex (G4)) structures in telomereTelomere and mitochondrialMitochondria DNA (mtDNA) are the subjects of intense current research interest. The telomereTelomere, a complex of repetitive nucleotide sequences and binding proteins, is present at the end of chromosomesChromosome to safeguard genomic stability. G4G-quadruplex (G4), a noncanonicalNoncanonical DNA structure, forms in guanine-rich nucleic acid sequences such as immunoglobulin switch regions, telomeresTelomere, promoter regions (especially of oncogenes), and 5′-untranslated regions of genes. G4G-quadruplex (G4) motifs have been recognized as regulatory structures and are associated with genome instability and gene expression defects in the nuclear genome. The mitochondrial genome is a circular double-stranded DNA with significant asymmetry in strand composition. Mitochondrial DNA, especially the heavy (H) strand, is rich in guanine sequences and hence shows a strong propensity to form G4G-quadruplex (G4) structures that have been associated with mtDNA deletion breakpoints. mtDNA deletions are notably observed in various genetic disorders, mitochondrial dysfunctionMitochondrial dysfunction, cancer, and agingAging. TelomeraseTelomerase, which maintains telomereTelomere length, shuttles dynamically between different cellular locations. Under oxidative stressOxidative stress, telomeraseTelomerase localizes to mitochondriaMitochondria; however, little is known about the role of the interaction between the G4G-quadruplex (G4) structures in mtDNA and telomeraseTelomerase in determining mitochondrial function and fate. In this review, we cover the recent evidences supporting the potential of G4G-quadruplex (G4) structures and telomeraseTelomerase to regulate mitochondrial function and mitochondrial fate.
... In the presence of deoxy-Hb in the blood, a small fluctuation of hematocrit alone can directly affect the fMRI signal (Dent et al., 2016). Axial variation of hematocrit in the vessels has been theoretically suggested in relation to both neurovascular coupling (Chen & Pike, 2009;Kleinschmidt et al., 1996;Siegel et al., 2003) and sLFOs (Fagrell et al., 1980;Mayhew et al., 1996). Vasomotion drives local velocity fluctuations, termed "flowmotion" (Intaglietta, 1990), which reportedly accompany local hematocrit fluctuation (Fagrell et al., 1980;Hudetz et al., 1999). ...
As a complex system, the brain is considered to ultimately defy understanding through a reductionist approach. However, at present, scientists are busy addressing technical problems before considering such a theoretical dichotomy. Advances in neuroimaging methods have allowed observation of living brains at work, but many issues remain to be overcome; some fundamental, and some arising through poor utilization. For example, functional MRI suffers signal contamination by chaotic behavior of physiological confound. Nevertheless, functional neuroimaging is finally about to secure its position as a noninvasive method of physiological measurement that can be used to investigate in great detail, thus meeting the huge expectations from society.
... Thus, many researchers combined or compared the fNIRS information with others imaging modalities. The fNIRS result is being frequently compares with blood-oxygen-level-dependent (BOLD) fMRI as the BOLD response in fMRI is related to deoxyhemoglobin [2] [3][4][5][6][7][8]. Moreover, fNIRS monitoring were often used alongside PET scan to study the cerebral oxygen and cerebral blood flow during brain activation [9,10]. ...
Functional near infrared spectroscopy (fNIRS) is an imaging system that can measure hemodynamic changes of the brain. However, the system incapability to measure beyond the brain cortex region make it usage less appealing for in-depth brain studies. To overcome this, many researchers combine fNIRS with other imaging modalities to gain better understanding of the brain activities. In this paper, we described the theory of the registering fNIRS signals and positron emission tomography (PET) image method and performed experiments to validate it. The registration method was validated using specially designed phantom for fNIRS and PET. Polaris system was used to track the position of the phantom which is based on the Polaris markers during fNIRS and PET procedures. The Polaris markers share the same coordinate, thus the fNIRS and PET were calibrated to each other through these markers. To register the fNIRS signal on the PET image, the phantom position in fNIRS coordinate is translated to PET coordinate which allow the probe and the markers being coordinated in PET. Polaris markers were used as the references marker to determine the transformation matrices. The result shows that the fNIRS channel can be viewed on the PET image of the phantom. The transformation error from Polaris to PET is less than 1.00 mm and the precision test is less than 0.1mm while the accuracy is less than 2.8 mm. This result suggests that our theory on the registration method could be used for multimodal image registration between fNIRS and other modalities.
... The agreement between NIRS and MRI data has been confirmed previously, when both techniques were applied simultaneously to detect a decrease in dHb concentration due to functional activation of the primary sensorimotor cortex, indicating changes in cerebral blood oxygenation [158]. ...
Cerebral metabolic rate of oxygen (CMRO2) is a robust marker of brain health. It represents the amount of oxygen consumed by the brain, and it has been proved to be more sensitive indicator than oxygenation level and cerebral blood flow alone. Quantitative assessment of CMRO2 provides a useful insight into the viability of the brain tissue, the progression of a brain disease or action of a treatment. Therefore, there is a growing interest in developing methods that can quantify CMRO2, despite its complexity. Over the past years, many magnetic resonance imaging (MRI)-based methods and near-infrared spectroscopy (NIRS)-based methods have been developed for CMRO2 quantification. Here, we review the available approaches based on these two techniques, their advantages, and disadvantages. Examples of application of these approaches in animal models, neonates and adults under normal and different physiological conditions are provided. Physiological correlates such as cerebral blood flow, venous oxygen saturation and oxygen extraction fraction in addition to CMRO2 values found in the literature, are presented as well. We also show how the benefits of these two techniques can be combined to create a multimodal NIRS-MRI technique that can provide novel data, allowing better understanding of CMRO2 and oxidative metabolism in the brain.
... In all patients, typical neurovascular coupling (i.e. an increase in [HbO] and [HbT] and a simultaneous but less pronounced decrease in [HbR]) was observed over the contralateral SM [HbT] has been previously described in healthy subjects performing a motor task [91][92][93][94][95]. The corresponding increase in blood volume might be related to "cortical participation", i.e. an increase in cortical haemodynamics with no associated neurovascular coupling. ...
Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective treatment for idiopathic Parkinson’s disease. Despite recent progress, the mechanisms responsible for the technique’s effectiveness have yet to be fully elucidated. The purpose of the present study was to gain new insights into the interactions between STN-DBS and cortical network activity. We therefore combined high-resolution functional near-infrared spectroscopy with low-resolution electroencephalography in seven Parkinsonian patients on STN-DBS, and measured cortical haemodynamic changes at rest and during hand movement in the presence and absence of stimulation (the ON-stim and OFF-stim conditions, respectively) in the off-drug condition. The relative changes in oxyhaemoglobin [HbO], deoxyhaemoglobin [HbR], and total haemoglobin [HbT] levels were analyzed continuously. At rest, the [HbO], [HbR], and [HbT] over the bilateral sensorimotor (SM), premotor (PM) and dorsolateral prefrontal (DLPF) cortices decreased steadily throughout the duration of stimulation, relative to the OFF-stim condition. During hand movement in the OFF-stim condition, [HbO] increased and [HbR] decreased concomitantly over the contralateral SM cortex (as a result of neurovascular coupling), and [HbO], [HbR], and [HbT] increased concomitantly in the dorsolateral prefrontal cortex (DLPFC)—suggesting an increase in blood volume in this brain area. During hand movement with STN-DBS, the increase in [HbO] was over the contralateral SM and PM cortices was significantly lower than in the OFF-stim condition, as was the decrease in [HbO] and [HbT] in the DLPFC. Our results indicate that STN-DBS is associated with a reduction in blood volume over the SM, PM and DLPF cortices, regardless of whether or not the patient is performing a task. This particular effect on cortical networks might explain not only STN-DBS’s clinical effectiveness but also some of the associated adverse effects.
... Nach wie vor gelten die einem emotionalen Interferenz-Effekt zugrundeliegenden neuralen Grundlagen als ungeklärt (Feng et al. 2018 (Stolicyn et al. 2017). Dieses Modell stützt sich im Wesentlichen auf die automatic-attention hypothesis (Wentura et al. 2000), nach der bereits auf sehr früher Ebene automatisiert und in kürzester Zeit eine Aufmerksamkeitsverschiebung hin zu emotionalen Inhalten stattfindet (Lang et al. 1990a;LeDoux 1998 (Fox et al. 1986), was als charakteristisch für gesteigerte Arbeitsprozesse im Gehirn gilt (Kleinschmidt et al. 1996;Obrig et al. 2000;Villringer et al. 1993 1979;Kayser et al. 1997;Vanderploeg et al. 1987). In dieser Arbeit werden die ...
Hintergrund: Das Catechol-O-Methyltransferase-Gen (COMT) ist ein vielversprechendes Kandidatengen zur Untersuchung kognitiver und emotionaler Funktionen sowie deren pathologischer Veränderungen. Ein einzelner Basenaustausch in diesem Gen führt zu einer 3-4fach höheren COMT-Aktivität der Val Variante. Ein dadurch vermitteltes dopaminerges Defizit wird als relevanter Faktor für eine veränderte Hirnfunktion angenommen. Mit dem kognitiven Stroop-Paradigma wurden kognitive Verarbeitungsprozesse bisher gut erforscht. Zur Erfassung emotionaler Verarbeitungsprozesse wurde eine emotionale Variante entwickelt, deren neurale Grundlagen bislang weniger gut bekannt sind. Ziel: Unsere imaging genetics-Arbeit untersucht den Einfluss genetischer Varianten auf die neurale Funktion. Ziel dieser experimentellen Arbeit war es, den Einfluss des COMT-Polymorphismus (COMT-PM) auf die Frontalkortex-Funktion in ausgewählten Regionen von Interesse (ROI) zu erfassen und der Frage nachzugehen, ob das Val-Allel als Risiko-Allel zur Pathogenese einer Angststörung (AS) beitragen könnte. Zudem sollte die Tauglichkeit des emotionalen Stroop- Paradigmas als angstsensibles Messinstrument zur Untersuchung dieser Fragestellung geprüft werden. Demgegenüber steht die Annahme, das emotionale Stroop-Paradigma könnte lediglich eine Arbeitsgedächtnis (AG)-Aufgabe darstellen. Methoden: Mittels funktioneller Nahinfrarotspektroskopie (fNIRS) und ereigniskorrelierter Potentiale untersuchten wir 121 gesunde nach dem COMT- Val158Met-PM stratifizierte Probanden während eines kombiniert emotional- kognitiven Stroop-Paradigmas. Als neurale Korrelate von Exekutivfunktionen und AG-Aufgaben waren die ROI dabei der laterale präfrontale und inferiore Kortex, die auch mit emotionaler Regulation in Verbindung gebracht werden. Als Parameter der Reaktion des autonomen Nervensystems (ANS) diente die Erfassung der elektrodermalen Aktivität sowie die kontinuierliche Messung von Blutdruck, Herzfrequenz und Herzratenvariabilität. Ergebnisse: Bei allen drei COMT Varianten zeigte sich ein kognitiver Stroop-Effekt mit verlängerter Reaktionszeit und erhöhter Fehleranzahl während der Präsentation inkongruenter Farbworte. Als Reaktion des ANS stellte sich eine erhöhte elektrodermale Aktivität bei inkongruenten Farbworten dar. Die funktionelle Bildgebung ließ in den analysierten Regionen eine erhöhte präfrontale Aktivierung während der Verarbeitung inkongruenter Farbworte nachweisen. Es fanden sich keine Gruppenunterschiede im kognitiven Stroop-Paradigma. Der einzige emotionale Stroop-Effekt zeigte sich in der P300. Der einzig nachweisbare Gruppeneffekt stellte sich im emotionalen Stroop-Paradigma als höhere Fehleranzahl bei Met-Homozygoten verglichen mit Heterozygoten dar. Schlussfolgerung: Genetische Information und funktionelle Bildgebung kombiniert sollten ermöglichen, neurale Mechanismen zu definieren, die mit genetischen Varianten verlinkt sind. Die Ergebnisse bezogen auf die analysierten Regionen liefern keinen Hinweis auf ein Val-Allel assoziiertes Risiko für die Entwicklung einer AS. Damit gelingt es nicht, bisher gewonnene Ergebnisse zum Einfluss des COMT-PM auf die präfrontale Funktion zu replizieren. Fraglich ist jedoch, ob sich das emotionale Stroop-Paradigma zur Untersuchung dieser Frage eignet, da weder in den fNIRS-, noch in den autonomen oder Verhaltensdaten ein emotionaler Stroop-Effekt nachgewiesen werden konnte.
... fNIRS off ers some advantages over the most commonly used methods, namely functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Both fNIRS and fMRI rely on detecting the hemodynamic response, which starts around 2s after the event (or onset of the task in the block-design) and peaks around 6s after stimulus onset [56]. However, fNIRS has a better temporal resolution than fMRI. ...
Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical brain monitoring technology for mapping the functioning of the human cortex in response to sensory or motor activation. There is a growing interest in implementing fNIRS to monitor the cognitive performance of military pilots. The method relies on differences in hemoglobin absorption spectra depending on blood oxygenation. However, this method was relatively rarely utilized in aviation and aviation medicine. Therefore, we will provide a broad review of applying this method in various avenues of medicine and cognitive psychology, as well as cover its documented use in aviation and aviation medicine. In this review, we cover the following topics: 1) fNIRS in comparison to most commonly used neuroimaging methods, 2) fNIRS in the evaluation of human performance, 3) fNIRS application in aviation and aviation medicine, and 4) fNIRS-based Brain-Computer-Interface (BCI) to overcome cognitive restrictions and for optimizing pilot training. In conclusion, over the years, fNIRS has become a neuroimaging technique that contributes to making advances toward understanding the functioning of the human brain.
... In comparison with fMRI, one of the main benefits of fNIRS is that it allows measuring concentration changes in both HbO and HbR, while blood oxygenation leveldependent contrast functional fMRI (BOLD-fMRI) is only sensitive to changes in HbR concentration in blood. fNIRS activation studies show that, in normal adults, neuronal activation decreases HbR and increases both HbO and HbT [14,15]. However, this is not always the case with brain tumors, as Fujiwara et al. pointed out in 2004, when they measured evoked cerebral blood oxygenation (CBO) in brain tumors [16] in combination with BOLD-fMRI. ...
Functional near-infrared spectroscopy (fNIRS) is commonly used in studies of cerebral blood oxygenation and tissue hemodynamics. In recent years, fNIRS has awakened interest also as a potential tool for cancer diagnostics, particularly for breast cancer. Although clinical applications of fNIRS are still missing, they are anticipated to emerge because of fNIRS’ capability to detect microvasculature and blood oxygenation concentration related parameters, which in tumours often differ from those of healthy tissue. Furhermore, since fNIRS offers a broad range of contrast mechanisms for the study of cerebral metabolism, it can be used as an indirect diagnostic tool for brain cancer detection when combined, for instance, with magnetic resonance (MR) brain imaging techniques. In addition to being safe, portable, and affordable, fNIRS lends itself to both non-invasive and invasive applications in combination with other imaging modalities. This chapter provides a review of the application of fNIRS to cancer diagnostics and therapy monitoring. Of particular interest is breast cancer diagnostics where fNIRS has already shown great potential.
... More specifically, in fNIRS, a canonical hemodynamic response involves an increase in O 2 Hb accompanied by a decrease in HHb (see more below). For fNIRS-fMRI cross-validation studies, the reader can see Chance et al. (1998), Cui et al. (2011), Kleinschmidt et al. (1996), and Strangeman et al. (2002. Continuous wave fNIRS systems were the most commonly used in this review, but other approaches exist (frequencyresolved and time-resolved; see Scholkmann et al., 2014, for an overview). ...
Purpose
Functional brain imaging is playing an increasingly important role in the diagnosis and treatment of communication disorders, yet many populations and settings are incompatible with functional magnetic resonance imaging and other commonly used techniques. We conducted a systematic review of neuroimaging studies using functional near-infrared spectroscopy (fNIRS) with individuals with speech or language impairment across the life span. We aimed to answer the following question: To what extent has fNIRS been used to investigate the neural correlates of speech-language impairment?
Method
This systematic review was preregistered with PROSPERO, the international prospective register of systematic reviews (CRD42019136464). We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol for preferred reporting items for systematic reviews. The database searches were conducted between February and March of 2019 with the following search terms: (a) fNIRS or functional near-infrared spectroscopy or NIRS or near-infrared spectroscopy, (b) speech or language, and (c) disorder or impairment or delay.
Results
We found 34 fNIRS studies that involved individuals with speech or language impairment across nine categories: (a) autism spectrum disorders; (b) developmental speech and language disorders; (c) cochlear implantation and deafness; (d) dementia, dementia of the Alzheimer's type, and mild cognitive impairment; (e) locked-in syndrome; (f) neurologic speech disorders/dysarthria; (g) stroke/aphasia; (h) stuttering; and (i) traumatic brain injury.
Conclusions
Though it is not without inherent challenges, fNIRS may have advantages over other neuroimaging techniques in the areas of speech and language impairment. fNIRS has clinical applications that may lead to improved early and differential diagnosis, increase our understanding of response to treatment, improve neuroprosthetic functioning, and advance neurofeedback.
... To analyze oxygenation of intercostal muscle, a set of optodes was placed at the 7th left intercostal space and for VL, a set of optodes was placed at the belly of the vastus lateralis midway between the lateral epicondyle and greater trochanter of the femur. NIR optodes for Cox was positioned and fixed bilaterally on the forehead of the volunteers, approximately 3 cm from the midline and just above the supra-orbital crest, with an inter optode distance of 4.0 cm (Kleinschmidt et al., 1996;Obrig et al., 1996). The optodes were secured to the skin using double-sided adhesive tape, in order to guarantee the correct position and avoid displacement during the test. ...
Respiratory limitation can be a primary mechanism for exercise cessation in female athletes. This study aimed to assess the effects of IL on intercostal (IM), vastus lateralis (VL) and cerebral (Cox) oxygenation in women soccer players during high-intensity dynamic exercise. Ten female soccer players were randomized to perform in order two constant-load tests on a treadmill until the exhaustion time (Tlim) (100% of maximal oxygen uptake- V̇O2). They breathed freely or against a fixed inspiratory loading (IL) of 41 cm H2O (∼30% of maximal inspiratory pressure). Oxygenated (Δ[OxyHb]), deoxygenated (Δ[DeoxyHb]), total hemoglobin (Δ[tHb]) and tissue saturation index (ΔTSI) were obtained by NIRs. Also, blood lactate [La-] was obtained. IL significantly reduced Tlim (224 ± 54 vs 78 ± 20 sec; P < 0.05) and increased [La-], V̇O2, respiratory cycles and dyspnea when corrected to Tlim (P < 0.05). IL also resulted in decrease of Δ[OxyHb] of Cox and IM during exercise compared with rest condition. In addition, decrease of Δ[OxyHb] was observed on IM during exercise when contrasted with Sham (P < 0.05). Furthermore, significant higher Δ[DeoxyHb] of IM and significant lower Δ[DeoxyHb] of Cox were observed when IL was applied during exercise in contrast with Sham (P < 0.05). These results were accompanied with significant reduction of Δ[tHb] and ΔTSI of IM and VL when IL was applied (P < 0.05). High-intensity exercise with IL decreased respiratory and peripheral muscle oxygenation with negative impact on exercise performance. However, the increase in ventilatory work did not impact cerebral oxygenation in soccer players.
... The blood flow increase overcompensates oxygen consumption and elicits a focal hyperoxygenation resulting in an increase in [oxy-Hb] as well as a decrease in [deoxy-Hb] (Fox and Raichle, 1986). [Deoxy-Hb] represents the major contribution of the BOLD signal as measured by functional magnetic resonance imaging (fMRI) (Huppert et al., 2006;Kleinschmidt et al., 1996;Obrig and Villringer, 2003;Steinbrink et al., 2006); for opposing results see (Strangman et al., 2002). The used fNIRS system (NIRScout, NIRx Medizintechnik GmbH, Berlin) sends wavelengths at 860 and 730 nm and recorded data at 20.83 Hz. 6 light emitters and 8 light detectors were used to assess bilateral fronto-temporo-parietal brain areas. ...
The present study investigated neural correlates of implicit phonotactic processing in 18-month-old children that just reached an important step in language development: the vocabulary spurt. Pseudowords, either phonotactically legal or illegal with respect to their native language, were acoustically presented to monolingually German raised infants. Neural activity was simultaneously assessed by means of electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS). The former method excellently tracks fast processing mechanisms, whereas the latter reveals brain areas recruited. Results of the present study indicate that 18-month-olds recognize the linguistic properties of their native language based on phonotactics. This manifested in an increased N400 for legal compared to illegal pseudowords in the EEG conforming to adult-like mechanisms. Unfortunately, fNIRS findings did not support this discrimination ability. Possible methodological and brain maturational reasons might explain this null finding. This study provides evidence for the advantage of a multi-methodological approach in order to get a clear picture on neural language development.
... 68 For example, an increase or absence of changes in deoxy-Hb signals was also observed with increases in oxy-Hb. [70][71][72] Thus, the pattern of changes in deoxy-Hb signals and the applicability of the deoxy-Hb parameter should be carefully evaluated and discussed in further exploration. ...
Significance:
It has been reported that children with attention-deficit/hyperactivity disorder (ADHD) have impairment in recognition of angry but not of happy facial expressions, and they show atypical cortical activation patterns in response to facial expressions. However, little is known about neural mechanisms underlying the impaired recognition of facial expressions in school-aged children with ADHD and the effects of acute medication on their processing of facial expressions.
Aim and Approach: We measured the hemodynamic changes in the bilateral temporo-occipital areas of ADHD children observing the happy and angry facial expressions before and 1.5 h after methylphenidate (MPH) or placebo administration in a randomized, double-blind, placebo-controlled, crossover-design study.
Results: We found that regardless of medication, happy expressions induced increased oxyhemoglobin (oxy-Hb) responses in the right inferior occipital region, but not in the superior temporal region. For angry expressions, oxy-Hb responses increased after MPH administration, but not after placebo administration, in the left inferior occipital area, whereas there was no significant activation before MPH administration.
Conclusion: Our results suggest that (1) ADHD children consistently recruit the right inferior occipital regions to process happy expressions and (2) MPH administration to ADHD children enhances cortical activation in the left inferior occipital regions when they process angry expressions.
... fNIRS is a non-invasive, non-hazardous optical imaging technique that measures hemodynamic changes associated with brain metabolism (Villringer and Chance, 1997;Ferrari and Quaresima, 2012;Boas et al., 2014). It uses nearinfrared light to measure concentration changes in oxygenated and deoxygenated hemoglobin (HbO and HbR, respectively) in the cerebral cortex and its signals are spatially and temporally comparable to blood oxygenation level dependent (BOLD) signals measured by functional Magnetic Resonance Imaging (fMRI) (Kleinschmidt et al., 1996;Huppert et al., 2005Huppert et al., , 2006. The technique has found widespread use both in the research and clinical field despite its low penetration depth and spatial resolution, as it provides good portability, safety, and ecological validity at low-cost and is therefore well-suited for both experimental and real-life settings Yücel et al., 2017). ...
Within a decade, single trial analysis of functional Near Infrared Spectroscopy (fNIRS) signals has gained significant momentum, and fNIRS joined the set of modalities frequently used for active and passive Brain Computer Interfaces (BCI). A great variety of methods for feature extraction and classification have been explored using state-of-the-art Machine Learning methods. In contrast, signal preprocessing and cleaning pipelines for fNIRS often follow simple recipes and so far rarely incorporate the available state-of-the-art in adjacent fields. In neuroscience, where fMRI and fNIRS are established neuroimaging tools, evoked hemodynamic brain activity is typically estimated across multiple trials using a General Linear Model (GLM). With the help of the GLM, subject, channel, and task specific evoked hemodynamic responses are estimated, and the evoked brain activity is more robustly separated from systemic physiological interference using independent measures of nuisance regressors, such as short-separation fNIRS measurements. When correctly applied in single trial analysis, e.g., in BCI, this approach can significantly enhance contrast to noise ratio of the brain signal, improve feature separability and ultimately lead to better classification accuracy. In this manuscript, we provide a brief introduction into the GLM and show how to incorporate it into a typical BCI preprocessing pipeline and cross-validation. Using a resting state fNIRS data set augmented with synthetic hemodynamic responses that provide ground truth brain activity, we compare the quality of commonly used fNIRS features for BCI that are extracted from (1) conventionally preprocessed signals, and (2) signals preprocessed with the GLM and physiological nuisance regressors. We show that the GLM-based approach can provide better single trial estimates of brain activity as well as a new feature type, i.e., the weight of the individual and channel-specific hemodynamic response function (HRF) regressor. The improved estimates yield features with higher separability, that significantly enhance accuracy in a binary classification task when compared to conventional preprocessing—on average +7.4% across subjects and feature types. We propose to adapt this well-established approach from neuroscience to the domain of single-trial analysis and preprocessing wherever the classification of evoked brain activity is of concern, for instance in BCI.
... In the next, and final, experiment, the range of methodological tools used thus far in the thesis was extended considerably through the introduction of a brain imaging component, specifically, functional near-infrared spectroscopy (fNIRS; Kleinschmidt, Obrig, Requardt, Merboldt, Dirnagl, Villringer, & Frahm, 1996) was used to examine the role of brain regions associated with motor planning in nonword recall and learning. ...
Perceptual and motor processes are often viewed as peripheral systems, subservient
to central ‘higher level’ cognitive structures. An alternative approach adopted in the
present project characterises the cognitive functioning classically considered to be
supported by specialised modules as the product of the embodied processes involved
in organising environmental input into candidate-objects for action and producing
goal-appropriate behavioural outputs. The present project is the first to test the view
that learning novel verbal sequences—attributed classically to the operation of a
distinct phonological short-term store—can be reconstrued within this alternative
framework. Experiments 1-3 (Chapter 2) used the Hebb sequence learning
paradigm—the enhanced serial recall of a repeating sequence amongst otherwise
non-repeating sequences—and provided several lines of support for a perceptual-motor
account: First, Hebb sequence learning was attenuated when vocal-motor
planning of the sequence was restricted by requiring participants to utter an irrelevant
verbal sequence (‘articulatory suppression’) or when no recall-response was
required. The effect of suppression was less smaller auditory sequences, however,
suggesting that passive auditory perceptual organisation processes can independently
support auditory Hebb sequence learning. Second, Hebb sequence learning was
enhanced for phonologically similar compared to dissimilar sequences when that
learning was driven solely by motor planning. Third, disturbing the consistency of
the temporal grouping of the repeating sequence abolished learning but only when
that grouping was instantiated within a motor-plan. Fourth, demonstrating more
direct evidence for a contribution of passive perceptual organisation in learning an
auditory-verbal sequence, promoting the perceptual grouping of every-other-item in
the repeating sequence by presenting it in alternating male-female voices led to the
learning of those non-adjacent-item sub-sequences. Experiments 4-6 provided
evidence that motor planning processes also play a role in nonword learning in the
paired-associate paradigm, where lists of nonwords (together with known words) are
presented and recalled repeatedly. Nonword learning was attenuated when motor planning fluency was impeded either by articulatory suppression or as the result of
phonological similarity within or between the nonwords. The findings are discussed
in the context of the debate on modular versus embodied cognition as well as in
terms of their implications for word-form learning.
... The first attempts to combine the fNIRS with other modalities (in this case fMRI) were made in 1996 (Kleinschmidt et al. 1996). Simultaneous measurements using fNIRS and fMRI are used in many fields of science, i.e. cognitive psychology (Noah et al. 2015), motor function testing or the brain's resting condition. ...
Objectives. Functional near-infrared spectroscopy (fNIRS) is one of the fastest developing neuroimaging modalities. Features, such as non-invasiveness, simplicity of application and resistance to motion artefacts, allow to take measurements and to create scientific experiments imitating real life conditions. In this review, we want to focus on the potential of fNIRS in the fields of psychiatry, neurorehabilitation and physical exercise. Additionally, we present the advantages of fNIRS over other neuroimaging techniques like fMRI, PET and EEG/EMG. We also consider potential directions of development and challenges which emerge in front of the fNIRS society. Literature review. The main application in the discipline of neurorehabilitation is to monitor and to observe the repair mechanism of neurons after brain traumas. The non-invasiveness of infra-red light permits to investigate patients of both adult and child psychiatry. The utility of fNIRS as a diagnostic tool and a predictor is proven. Researchers are looking for functional abnormalities within the prefrontal cortex. fNIRS creates new possibilities in terms of exploration of the physical exercise. Recent articles consider which type of effort has the best effect on the hemodynamic response in the cortex. It seems that investigating the impact of the physical activity in group of psychiatric patients is an interesting direction. Conclusions. Currently, we are at the breakthrough in the fNIRS technology. The number of new studies, more precise methods of data analysis, and availability of good quality systems help us to better understand how to design scientific experiments properly and reliably measure the activity of the cerebral cortex.
... Over the past decades, many research groups have conducted extensive studies in the field of diffuse optic tomography (DOT) by using fNIRS, and developed statistical analyses toolboxes to enhance the fNIRS signal quality based on the general linear models (GLM) [6][7][8][9][10][11][12][13][14]. GLM is one of the most extensively used models that represent data in a linear combination form, and constitutes a standard method for analyzing the fMRI data. ...
Brain cortical activation analysis is important for understanding the causes of neurological disorders and relevant brain mechanisms. Over the past decades, various studies have been published on the brain functional activities and cortical activation analysis using functional near-infrared spectroscopy (fNIRS). The fNIRS yields outputs similar to the blood-oxygen-level-dependent (BOLD) signals of the functional magnetic resonance imaging (fMRI) and has an advantage that can measure higher temporal resolution than fMRI. In this paper, we developed a MATLAB toolbox, referred to as ActiView, for analyzing the cortical activation on realtime. Although the existence of numerous analysis toolboxes for fNIRS, most of these are not easy to use because they involve numerous steps, coefficients, anatomic information, 3-dimensions coordinator, and related files. Given that ActiView consists of a simple and intuitive graphical user interface (GUI), users can lightly analyze the brain cortical activation by using fNIRS signals. To investigate the developed toolbox, the hand clenching task experiment---extensively used in brain functional activity studies---was applied. The experimental results elicited the realtime brain cortical activation results compare to the offline brain cortical activity that was analyzed using NIRS SPM---one of the most extensively used NIRS analysis toolboxes.
... Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive, nonionizing optical imaging technique that measures the hemodynamic changes associated with brain activity Ferrari and Quaresima, 2012;Villringer and Chance, 1997). It uses light in the near-infrared region to measure the concentration changes in oxygenated and deoxygenated hemoglobin (HbO and HbR respectively) in the cerebral cortex, a signal that is spatially and temporally comparable to blood oxygenation level dependent (BOLD) signals measured by functional Magnetic Resonance Imaging (fMRI) (Huppert et al., , 2005Kleinschmidt et al., 1996). Despite its low penetration depth and spatial resolution, the technique has found widespread use both in the research and clinical field due to its portability, safety, low-cost and the ecological validity that it provides in experimental and real-life settings Yücel et al., 2017). ...
For the robust estimation of evoked brain activity from functional Near Infrared Spectroscopy (fNIRS) signals, it is crucial to reduce nuisance signals from systemic physiology and motion. The current best practice incorporates short separation (SS) fNIRS measurements as regressors in a General Linear Model (GLM). However, several challenging signal characteristics such as non-instantaneous and non-constant coupling are not yet addressed by this approach and additional auxiliary signals are not optimally exploited. We have recently introduced a new methodological framework for the unsupervised multivariate analysis of fNIRS signals using Blind Source Separation (BSS) methods. Building onto the framework, in this manuscript we show how to incorporate the advantages of regularized temporally embedded Canonical Correlation Analysis (tCCA) into the supervised GLM. This approach allows flexible integration of any number of auxiliary modalities and signals. We provide guidance for the selection of optimal parameters and auxiliary signals for the proposed GLM extension. Its performance in the recovery of evoked HRFs is then evaluated using both simulated ground truth data and real experimental data and compared with the GLM with short separation regression. Our results show that the GLM with tCCA significantly improves upon the current best practice, yielding significantly better results across all applied metrics: Correlation (HbO max. +45%), Root Mean Squared Error (HbO max. -55%), F-Score (HbO up to 3.25-fold) and p-value as well as power spectral density of the noise floor. The proposed method can be incorporated into the GLM in an easily applicable way that flexibly combines any available auxiliary signals into optimal nuisance regressors. This work has potential significance both for conventional neuroscientific fNIRS experiments as well as for emerging applications of fNIRS in everyday environments, medicine and BCI, where high Contrast to Noise Ratio is of importance for single trial analysis.
... Blood oxygen saturation, sO 2 , defined as the ratio of oxygenated to total hemoglobin concentration, is an important physiological indicator of tissue function and pathology and therefore has many clinical and preclinical applications. Examples of such applications include locating regions of brain activation, [1][2][3] and characterizing and staging tumors. 4,5 Optical methods for estimating blood oxygenation are also in common use, with pulse-oximetry 6 routinely used to monitor a patient's systemic blood oxygenation, and near-infrared (NIR) spectroscopy 7 and diffuse optical tomography 8 used, for example, for stroke characterization 9 and functional studies of brain activation in neonates. ...
Linear spectroscopic inversions, in which photoacoustic amplitudes are assumed to be directly proportional to absorption coefficients, are widely used in photoacoustic imaging to estimate blood oxygen saturation because of their simplicity. Unfortunately, they do not account for the spatially varying wavelength-dependence of the light fluence within the tissue, which introduces "spectral coloring," a potentially significant source of error. However, accurately correcting for spectral coloring is challenging, so we investigated whether there are conditions, e.g., sets of wavelengths, where it is possible to ignore the spectral coloring and still obtain accurate oxygenation measurements using linear inversions. Accurate estimates of oxygenation can be obtained when the wavelengths are chosen to (i) minimize spectral coloring, (ii) avoid ill-conditioning, and (iii) maintain a sufficiently high signal-to-noise ratio (SNR) for the estimates to be meaningful. It is not obvious which wavelengths will satisfy these conditions, and they are very likely to vary for different imaging scenarios, making it difficult to find general rules. Through the use of numerical simulations, we isolated the effect of spectral coloring from sources of experimental error. It was shown that using wavelengths between 500 nm and 1000 nm yields inaccurate estimates of oxygenation and that careful selection of wavelengths in the 620- to 920-nm range can yield more accurate oxygenation values. However, this is only achievable with a good prior estimate of the true oxygenation. Even in this idealized case, it was shown that considerable care must be exercised over the choice of wavelengths when using linear spectroscopic inversions to obtain accurate estimates of blood oxygenation. This suggests that for a particular imaging scenario, obtaining accurate and reliable oxygenation estimates using linear spectroscopic inversions requires careful modeling or experimental studies of that scenario, taking account of the instrumentation, tissue anatomy, likely sO
2
range, and image formation process.
Characterization of cortical activation patterns during movements in healthy adults may help our understanding of how the injured brain works. Upper limb motor tasks are commonly used to assess impaired motor function and to predict recovery in individuals with neurological disorders such as stroke. This study aimed to explore cortical activation patterns associated with movements of the hand and shoulder using functional near-infrared spectroscopy (fNIRS) and to demonstrate the potential of this technology to distinguish cerebral activation between distal and proximal movements. Twenty healthy, right-handed participants were recruited. Two 10-s motor tasks (right-hand opening-closing and right shoulder abduction-adduction) were performed in a sitting position at a rate of 0.5 Hz in a block paradigm. We measured the variations in oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR) concentrations. fNIRS was performed with a 24-channel system (Brite 24®; Artinis) that covered most motor control brain regions bilaterally. Activation was mostly contralateral for both hand and shoulder movements. Activation was more lateral for hand movements and more medial for shoulder movements, as predicted by the classical homunculus representation. Both HbO2 and HbR concentrations varied with the activity. Our results showed that fNIRS can distinguish patterns of cortical activity in upper limb movements under ecological conditions. These results suggest that fNIRS can be used to measure spontaneous motor recovery and rehabilitation-induced recovery after brain injury. The trial was restropectively registered on January 20, 2023: NCT05691777 (clinicaltrial.gov).
PURPOSE: There is growing attention on a neuroimaging method called near-infrared spectroscopy (NIRS), which enables the monitoring of task-related regional hemodynamic responses in the brain. The basic principles and appropriate experimental conditions should be explained to eliminate potent contaminations caused by exercise itself and to summarize well-organized recent studies focusing on the interaction between exercise and cognition before applying this noninvasive neuroimaging method to various studies in the field of Exercise Science.METHODS: A comprehensive search of PubMed, Web of Science, and Google Scholar was performed to obtain recent studies examining the effects of exercise (or physical activity) on the executive functions localized in the prefrontal cortex by adopting the NIRS system.RESULTS: NIRS system enables exercise scientists to measure regional brain activity to investigate the effects of exercise on cognition and its neural substrates. Numerous studies have revealed that higher physical activity (or fitness) levels are related to better performance with increased prefrontal cortical activation during a task. Moreover, several longitudinal exercise intervention studies have demonstrated improved executive performance without increased task-related brain activation, particularly among older adults.CONCLUSIONS: NIRS neuroimaging studies support the notion that exercise has beneficial effects on executive function, with exerciseelicited functional changes in the prefrontal cortex.
We report on the first three-dimensional, volumetric, tomographic localization of changes in the concentration of oxyhemoglobin and deoxyhemoglobin in the brain. To this end we have developed a model-based iterative image reconstruction scheme that employs adjoint differentiation methods to minimize the difference between measured and predicted data. To illustrate the performance of the technique, the three-dimensional distribution of changes in the concentration of oxyhemoglobin and deoxyhemoglobin during a Valsalva maneuver are visualized. The observed results are consistent with previously reported effects concerning optical responses to hemodynamic perturbations.
Background: functional near-infrared spectroscopy (fNIRS) is an increasingly popular tool to study cortical activity during movement and gait that requires further validation. This study aimed to assess (1) whether fNIRS can detect the difficult-to-measure leg area of the primary motor cortex (M1) and distinguish it from the hand area; and (2) whether fNIRS can differentiate between automatic (i.e., not requiring one's attention) and non-automatic movement processes. Special attention was attributed to systemic artifacts (i.e., changes in blood pressure, heart rate, breathing) which were assessed and corrected by short channels, i.e., fNIRS channels which are mainly sensitive to superficial scalp hemodynamics. Methods: Twenty-three seated, healthy participants tapped four fingers on a keyboard or tapped the right foot on four squares on the floor in a specific order given by a 12-digit sequence (e.g., 434141243212). Two different sequences were executed: a beforehand learned (i.e., automatic) version and a newly learned (i.e., non-automatic) version. A 36-channel fNIRS device including 12 short channels covered multiple motor-related cortical areas including M1. The fNIRS data were analyzed with a general linear model (GLM). Correlation between the expected functional hemodynamic responses (i.e. task regressor) and the short channels (i.e. nuisance regressors), necessitated performing a separate short channel regression instead of integrating them in the GLM. Results: Consistent with the M1 somatotopy, we found significant HbO increases of very large effect size in the lateral M1 channels during finger tapping (Cohen's d = 1.35, p
In a system as complex as the human brain, one cannot conceive of meaningful events involving a change in a single observable (physiological) parameter. Therefore, achieving the ultimate aim of a complete understanding of brain events and brain activity in general will require the integration of a variety of observations related to these events. Multimodal imaging, or more generally measurements whereby data from various types of instruments are brought together, has arisen from this realisation, partly because some events are best observed in one modality and the investigator is interested in another (e.g. a more recently developed modality) and to be honest sometimes as a response to the technical challenge of combining modalities for simultaneous observations. Fundamentally, multimodal imaging should allow the investigator to address the question: what happens to brain observable Z when observable X changes (or event Y occurs)? In the second half of the twentieth century, and particularly since the 1990s, a rapid development of noninvasive functional and structural brain imaging methods has occurred. While some of these developments have resulted from gradual improvements in some methods, other developments have led to completely new approaches for measuring brain activity, affording new types of information about the brain. In the former case, the older methods were eventually replaced [e.g. scintigraphic methods by positron emission tomography (PET) and SPECT or low-field MRI (magnetic resonance imaging) by higher-field MRI]. In the latter case, however, newer developments have not replaced older ones; rather, they have been added to an ever-larger orchestra of functional and structural neuroimaging methods consisting of techniques that offer complementary information about the brain. An overview of currently available methods for noninvasive brain imaging and the principle that each exploits is given.
The exploration of human brain function has always been a research hotspot in the field of neuroscience. The concept of a neurovascular unit suggests that cerebral microcirculation can be used as a reliable signal to reflect neural function. Accordingly, functional imaging techniques based on the neurovascular unit are very promising because of their ability to reveal neurovascular coupling and evaluate the functional rehabilitation of cerebrovascular diseases represented by stroke. In the present review, we first describe the role of the neurovascular unit in the injury and repair processes after stroke. We then briefly introduce the relative characteristics and advantages of representative neurovascular unit-based functional imaging. Finally, we summarized the value of these techniques in the evaluation of neural networks after stroke.
Significance
There is a longstanding recommendation within the field of fNIRS to use oxygenated (HbO2) and deoxygenated (HHb) hemoglobin when analyzing and interpreting results. Despite this, many fNIRS studies do focus on HbO2 only. Previous work has shown that HbO2 on its own is susceptible to systemic interference and results may mostly reflect that rather than functional activation. Studies using both HbO2 and HHb to draw their conclusions do so with varying methods and can lead to discrepancies between studies. The combination of HbO2 and HHb has been recommended as a method to utilize both signals in analysis.
Aim
We present the development of the hemodynamic phase correlation (HPC) signal to combine HbO2 and HHb as recommended to utilize both signals in the analysis. We use synthetic and experimental data to evaluate how the HPC and current signals used for fNIRS analysis compare.
Approach
About 18 synthetic datasets were formed using resting-state fNIRS data acquired from 16 channels over the frontal lobe. To simulate fNIRS data for a block-design task, we superimposed a synthetic task-related hemodynamic response to the resting state data. This data was used to develop an HPC-general linear model (GLM) framework. Experiments were conducted to investigate the performance of each signal at different SNR and to investigate the effect of false positives on the data. Performance was based on each signal’s mean T-value across channels. Experimental data recorded from 128 participants across 134 channels during a finger-tapping task were used to investigate the performance of multiple signals [HbO2, HHb, HbT, HbD, correlation-based signal improvement (CBSI), and HPC] on real data. Signal performance was evaluated on its ability to localize activation to a specific region of interest.
Results
Results from varying the SNR show that the HPC signal has the highest performance for high SNRs. The CBSI performed the best for medium-low SNR. The next analysis evaluated how false positives affect the signals. The analyses evaluating the effect of false positives showed that the HPC and CBSI signals reflect the effect of false positives on HbO2 and HHb. The analysis of real experimental data revealed that the HPC and HHb signals provide localization to the primary motor cortex with the highest accuracy.
Conclusions
We developed a new hemodynamic signal (HPC) with the potential to overcome the current limitations of using HbO2 and HHb separately. Our results suggest that the HPC signal provides comparable accuracy to HHb to localize functional activation while at the same time being more robust against false positives.
Advancements in Microelectromechanical systems (MEMS) have enabled the manufacture of affordable and efficient wearable devices. In sensor-based gait analysis, motion and biofeedback sensor devices are easily attached to different parts of the body. Instrumentation of gait using different sensor technologies enables researchers and clinicians to capture high-resolution quantitative motion data within and beyond the lab. Integration of advanced sensor technologies provides objective and rater-independent multimodal outcomes that complement established clinical examination. Multi-modal data capture in ecologically valid, patient-relevant habitual settings opens new possibilities to monitor fluctuating and rare incidents by informing different aspects of impaired gait. Interconnected device communication and the Internet of Things (IoT) provide the infrastructural platform to enable remote gait assessment. However, an extended period of motion data recorded by different sensor technologies results in a vast amount of unlabelled data. Computational methods and artificial intelligence techniques (e.g., data mining) provide opportunities to manage data collected in unsupervised environments. Although technological advancement and algorithms promote remote gait assessment, more work needs to be done in terms of analytical and clinical validation to achieve robust and reliable gait analysis tools that contribute to better rehabilitation and treatment.
Compared to functional magnetic resonance imaging (fMRI), functional near infrared spectroscopy (fNIRS) has several advantages that make it particularly interesting for neurofeedback (NFB). A pre-requisite for NFB applications is that with fNIRS, signals from the brain region of interest can be measured. This study focused on the supplementary motor area (SMA). Healthy older participants (N = 16) completed separate continuous-wave (CW-) fNIRS and (f)MRI sessions. Data were collected for executed and imagined hand movements (motor imagery, MI), and for MI of whole body movements. Individual anatomical data were used to (i) define the regions of interest for fMRI analysis, to (ii) extract the fMRI BOLD response from the cortical regions corresponding to the fNIRS channels, and (iii) to select fNIRS channels. Concentration changes in oxygenated (Δ[HbO]) and deoxygenated (Δ[HbR]) hemoglobin were considered in the analyses. Results revealed subtle differences between the different MI tasks, indicating that for whole body MI movements as well as for MI of hand movements Δ[HbR] is the more specific signal. Selection of the fNIRS channel set based on individual anatomy did not improve the results. Overall, the study indicates that in terms of spatial specificity and task sensitivity SMA activation can be reliably measured with CW-fNIRS.
Functional near-infrared spectroscopy (fNIRS) is a promising neuroimaging technology. The fNIRS classification problem has always been the focus of the brain-computer interface (BCI). Inspired by the success of Transformer based on self-attention mechanism in the fields of natural language processing and computer vision, we propose an fNIRS classification network based on Transformer, named fNIRS-T. We explore the spatial-level and channel-level representation of fNIRS signals to improve data utilization and network representation capacity. Besides, a preprocessing module, which consists of one-dimensional average pooling and layer normalization, is designed to replace filtering and baseline correction of data preprocessing. It makes fNIRS-T an end-to-end network, called fNIRS-PreT. Compared with traditional machine learning classifiers, convolutional neural network (CNN), and long short-term memory (LSTM), the proposed models obtain the best accuracy on three open-access datasets. Specifically, in the most extensive ternary classification task (30 subjects) that includes three types of overt movements, fNIRS-T, CNN, and LSTM obtain 75.49%, 72.89%, and 61.94% on test sets, respectively. Compared to traditional classifiers, fNIRS-T is at least 27.41% higher than statistical features and 6.79% higher than well-designed features. In the individual subject experiment of the ternary classification task, fNIRS-T achieves an average subject accuracy of 78.22% and surpasses CNN and LSTM by a large margin of +4.75% and +11.33%. fNIRS-PreT using raw data also achieves competitive performance to fNIRS-T. Therefore, the proposed models improve the performance of fNIRS-based BCI significantly.
Near-infrared spectroscopy (NIRS) techniques can provide noninvasive in vivo hemoglobin oxygenation information but suffer from relatively low resolution in biological tissue imaging. Microwave-induced thermoacoustic tomography (TAT) can produce high-resolution images of the biological tissue anatomy but offer limited physiological information of samples because of the single species of the chromophore it maps. To overcome these drawbacks and take advantage of the merits of the two independent techniques, we built a dual-modality system by combining a NIRS system and a TAT system to image biological tissues. A series of phantom trials were carried out to demonstrate the performance of the new system. The spatial resolution is about 1 mm, with a penetration depth of at least 17.5 mm in the human subject. A cohort of five healthy subjects was recruited to conduct real-time forearm venous and arterial cuff occlusion experiments. Numerous results showed that this dual-modality system could measure oxygen metabolism and simultaneously provide anatomical structure changes of biological tissues. We also found that although the hemoglobin concentration varied consistently with many other published papers, the TAT signal intensity of veins showed an opposite variation tendency in the venous occlusion stage compared with other existing work. A detailed explanation is given to account for the discrepancy, thus, providing another possibility for the forearm experiments using TAT. Furthermore, based on the multiple types of information afforded by this dual-modality system, a pilot clinical application for the diagnosis of anemia is discussed.
Cerebral hypoxia is a severe injury caused by oxygen deprivation to the brain. Hypoxia in the neonatal period increases the risk for the development of neurological disorders, including hypoxic-ischemic encephalopathy, cerebral palsy, periventricular leukomalacia, and hydrocephalus. It is crucial to recognize hypoxia as soon as possible because early intervention improves outcomes. Photoacoustic imaging, using at least two wavelengths, through a spectroscopic analysis, can measure brain oxygen saturation. Due to the spectral coloring effect arising from the dependency of optical properties of biological tissues to the wavelength of light, choosing the right wavelength-pair for efficient and most accurate oxygen saturation measurement and consequently quantifying hypoxia at a specific depth is critical. Using a realistic neonate head model and Monte Carlo simulations, we found practical wavelength-pairs that quantified regions with hypoxia most accurately at different depths down to 22 mm into the cortex neighboring the lateral ventricle. We also demonstrated, for the first time, that the accuracy of the sO2 measurement can be increased by adjusting the level of light energy for each wavelength-pair. Considering the growing interest in photoacoustic imaging of the brain, this work will assist in a more accurate use of photoacoustic spectroscopy and help in the clinical translation of this promising imaging modality. Please note that explaining the effect of acoustic aberration of the skull is not in the scope of this study.
Aim:
The aim of the current study was to assess whether executive function and prefrontal oxygenation are dependent on fitness level and age in older adults.
Methods:
Twenty-four healthy males aged between 55 and 69 years old were recruited for this study. They were stratified by age, leading to the creation of two groups: 55-60 years old and 61-69 years old. A median split based on CRF creates higher- and lower-fit categories of participants. Cerebral oxygenation was assessed using functional near-infrared spectroscopy (fNIRS) during a computerized Stroop task. Accuracy (% of correct responses) and reaction times (ms) were used as behavioural indicators of cognitive performances. Changes in oxygenated (∆HbO2) and deoxygenated (∆HHb) hemoglobin were measured to capture neural changes. Repeated measures ANOVAs (CRF x Age x Stroop conditions) were performed to test the null hypothesis of an absence of interaction between CRF, Age and executive performance. Results: We also found an interaction between CRF and age on reaction times (p = .001), in which higher fitness levels were related to faster reaction times in the 61-69 year olds but not in the 55-60 year olds. Regarding ΔHHb, the ANOVA revealed a main effect of CRF in the right PFC (p = .04), in which higher-fit participants had a greater ΔHHb than the lower-fit (d = 1.5). We also found fitness by age interaction for ΔHHb in the right PFC (p = .04).
Conclusion:
Our results support the positive association of CRF on cerebral oxygenation and Stroop performance in healthy older males. They indicated that high-fit individuals performed better in the 61-69 year olds group, but not in the 55-60 years old group. We also observed a greater PFC oxygenation change (as measured by ΔHHb) in the high-fit individuals.
Near-infrared spectroscopy (fNIRS) measures concentrations of oxygenated (HbO) and deoxygenated (HbR) hemoglobin in the brain. Recently, we demonstrated its potential also for measuring concentrations of cerebral water (cH2O). We performed fNIRS measurements during rest to study fluctuations in concentrations of cH O, HbO and HbR in 33 well-rested healthy control subjects (HC) and 18 acutely sleep-deprived HC. Resting-state fNIRS signal was filtered in full-band, cardiac, respiratory, low-, and very-low-frequency bands. The sum of HbO and HbR constitutes the regional cerebral blood volume (CBV). CBV and cH2O concentrations were analyzed via temporal correlation and phase synchrony. Fluctuation in concentrations of cH2O and CBV was strongly anti-correlated across all frequency bands in both frontal and parietal cortices. Fluctuation in concentrations of cH2O and CBV showed neither a completely synchronous nor a random phase relationship in both frontal and parietal cortices. Acutely sleep-deprived subjects did not show significant differences in temporal correlation or phase synchrony between fluctuations in cH2O and CBV concentrations compared with well-rested HC. The reciprocal interrelation between fluctuations in CBV and cH2O concentrations is consistent with the Munro-Kellie doctrine of constant intracranial volume. This coupling may constitute a functional mechanism underlying glymphatic circulation, which persists despite acutely disturbed sleep patterns.
This study aimed to explore and analyze research trends and frontiers on functional near-infrared spectroscopy (fNIRS) in the past 20 years and identify collaboration networks. fNIRS-related publications from 2000 to 2019 were retrieved from the Web of Science database. A total of 1727 publications satisfied the search criteria. Bibliometric visualization analysis of active authors, journals, institutions, countries, references, and keywords were conducted. The number of annual related publications remarkably increased over the years. Fallgatter published the largest number of fNIRS-related papers (83). Neuroimage not only had the largest number of papers published in the first 10 journals (157 articles) but also had the highest impact factor (IF 2018 = 5.812). The University of Tubingen had the highest number of fNIRS-related publications in the past 20 years. The United States ranked first in terms of comprehensive influence in this field. In recent years, burst keywords (e.g., infant, social interaction, and older adult) and a series of references with citation burst provided clues on research frontiers.
We report on the first three dimensional tomographic localization of hemodynamic effects in the brain with diffuse optical tomography. Using a model-based iterative image reconstruction algorithms we localize spatial changes in oxy and deoxyhemoglobin.
Aims: Recent research suggests that aerobic exercise can be performed safely within the first week following a concussion injury and that early initiation of exercise may speed recovery. To better understand the physiological changes during a concussion, we tested the hypothesis that mild-to-intense exercise testing can be performed within days immediately following injury, and can be used to discern differences between the concussed and normal healthy state. Thus, the purpose was to observe the cerebral hemodynamic responses to incremental exercise testing performed acutely post-concussion in high-performance athletes.
Methods: This study was a within- and between-experimental design, with seven male university ice hockey teams participating. A subgroup of five players acted as control subjects (CON) and was tested at the same time as the 14 concussed (mTBI) players on Day 2, 4, and 7 post-concussion. A 5-min resting baseline and 5-min exercise bouts of mild (EX1), moderate (EX2), and high (EX3) intensity exercise were performed on a cycle ergometer. Near-infrared spectroscopy was used to monitor pre-frontal cortex oxy-haemoglobin (HbO2), deoxy-haemoglobin (HHb), and total blood volume (tHb) changes.
Results: ANOVA compared differences between testing days and groups, and although large percentage changes in HbO2 (20–30%), HHb (30–40%), and tHb (30–40%) were recorded, no significant (p ≤ 0.05) differences in cerebral hemodynamics occurred between mTBI vs. CON during aerobic exercise testing on any day post-injury. Furthermore, there was a linear relationship between exercise intensity vs. cerebral hemodynamics during testing for each day (r2 = 0.83–0.99).
Conclusion: These results demonstrate two novel findings: (1) mild-to-intense aerobic exercise testing can be performed safely as early as Day 2 post-concussion injury in a controlled laboratory environment; and (2) evidence-based objective measures such as cerebral hemodynamics can easily be collected using near-infrared spectroscopy (NIRS) to monitor physiological changes during the first-week post-injury. This research has important implications for monitoring physiological recovery post-injury and establishing new rehabilitation guidelines.
Methods for measuring blood flow by n.m.r. have been reviewed (Jones & Child, 1976), but for our purposes it was necessary that the measurement be independent of T2. We have measured flow by the rate of replacement of saturated sample in the coil by unsaturated sample. The measurement is achieved in three stages. Firstly blood momentarily inside the radiofrequency coil is saturated by the sequence pulsed magnetic-field gradient-90° pulse-pulsed magnetic-field gradient. Next there is a delay during which unsaturated blood flows into the coil. Finally, this volume of unsaturated blood is determined by a 90° sampling pulse.
1. We used conventional gradient echo magnetic resonance imaging (MRI) at high field strength (4 Tesla) to functionally image the right motor cortex in six normal human subjects during the performance of a sequence of self-paced thumb to digit oppositions with the left hand (contralateral task), the right hand (ipsilateral task), and both hands (bilateral task). 2. A localized increase in activity in the lateral motor cortex was observed in all subjects during the task. The area of activation was similar in the contralateral and bilateral tasks but 20 times smaller in the ipsilateral task. The intensity of activation was 2.3 times greater in the contralateral than the ipsilateral task.
This unusual volume represents the work of one of the leading investigators of cerebrovascular physiology and pathology in the Soviet Union. His ideas are not well known to Western science. Many of them are unorthodox, and in many instances he raises more questions than he answers. His book provides a most welcome and rare glimpse into an important area of research as it is carried out in the Georgian Republic of the Soviet Union.
The book consists of the results of many experiments by the author and his collaborators as well as illustrative, penetrating, and at times provocative discussions of the theoretical aspects of the problems. The author is familiar with the Western literature on this complicated subject and draws freely on such publications, which he skillfully incorporates into many of his theoretical proposals. His belief that cerebral arteries, arterioles, and capillaries may under certain circumstances respond to specific controls
Functional activation of the human visual and motor system was studied by magnetic resonance imaging (MRI) at 2.0 T using dynamic series of oxygenation-sensitive gradient-echo images at high spatial resolution. Activation maps were computed by correlating signal intensity time courses with a reference waveform on a pixel-by-pixel basis. Although this strategy readily demonstrates stimulus-related functional cooperativity of activated regions in thresholded maps of correlation coefficients, intertrial variability in the underlying distributions of correlation coefficients precludes the use of correlation coefficients as direct thresholds for defining activation. Because stimulus-related effects emerge as positive deviations from an otherwise symmetric distribution of correlation coefficients, invariance against intertrial differences as well as adequate visualization of activated areas may be achieved by the following procedure. First, a symmetrized noise distribution is reconstructed from the actual activation map that allows rescaling of correlation coefficients into percentile ranks with respect to the integral of the noise distribution. Second, a high percentile rank (or correspondingly low error probability) can be used as threshold to define primary sites of activation with high specificity. And third, the spatial extent of activation may be delineated by adding directly neighboring pixels with lower values provided their correlation coefficients are high enough to contribute to the positive deviation from the noise distribution. The outlined approach yields robust activation maps but still awaits a more thorough statistical treatment of activation in MRI correlational mapping.
Image processing strategies for functional magnetic resonance imaging (FMRI) data sets acquired using a gradient-recalled echo-planar imaging sequence are considered. The analysis is carried out using the mathematics of vector spaces. Data sets consisting of N sequential images of the same slice of brain tissue are analyzed in the time-domain and also, after Fourier transformation, in the frequency domain. A technique for thresholding is introduced that uses the shape of the response in a pixel compared with the shape of a reference waveform as the decision criterion. A method is presented to eliminate drifts in data that arise from subject movement. The methods are applied to experimental FMRI data from the motor—cortex and compared with more conventional image—subtraction methods. Several finger motion paradigms are considered in the context of the various image processing strategies. The most effective method for image processing involves thresholding by shape as characterized by the correlation coefficient of the data with respect to a reference waveform followed by formation of a cross-correlation image. Emphasis is placed not only on image formation, but also on the use of signal processing techniques to characterize the temporal response of the brain to the paradigm.
Functional mapping of human brain activation has been accomplished at high spatial and temporal resolution (voxel size 4.9 microliter, temporal increment 100 ms). The approach was based on oxygenation-sensitive long-echo time FLASH MRI sequences synchronized to multiply repeated cycles of visual stimulation in a CINE acquisition mode. This high temporal resolution revealed that stimulus-related signal intensity changes in human visual cortex display an initial latency followed by increases extending over several seconds. Furthermore, the temporal characteristics of the complete CINE MRI signal time course depended on the absolute and relative durations of activation and control periods and, for example, caused an apparent absence of a poststimulation "under-shoot" phenomenon. Complementing hyperoxygenation due to rapid hemodynamic adjustments, these results suggest signal intensity modulation by enhanced oxygen consumption and concomitant deoxygenation during prolonged and/or repetitive stimulation.
The use of optical spectroscopy for the non-invasive monitoring of tissue oxygenation and metabolism is well established (Chance et al., 1975). Historically because of the high absorption by tissue of light in the visible range, optical monitoring was often restricted to measurements of reflected light (Jöbsis et al., 1977). Subsequently Jöbsis showed that by using near infrared light (NIR), tissue absorption became sufficiently low to make transillumination of the cat head possible (Jöbsis, 1977). In the near infrared region (700–1300 nm) there is sufficient spectral information available to permit changes in the concentration of haemoglobin and cytochrome aa3 to be calculated, and hence changes in the oxygenation state of the brain (Brazy et al., 1985, 1986; Ferrari et al., 1986; Fox et al., 1985). This technique is now used routinely to monitor cerebral oxygenation and haemodynamics in the human newborn infant (Wyatt et al., 1986; Edwards et al., 1988), using an instrument designed to transilluminate the heads of most newborn infants (Cope and Delpy, 1988). This instrument allows for measurements through heads up to 8–9 cm in diameter.
Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high fields, we demonstrate in vivo images of brain microvasculature with image contrast reflecting the blood oxygen level. This blood oxygenation level-dependent (BOLD) contrast follows blood oxygen changes induced by anesthetics, by insulin-induced hypoglycemia, and by inhaled gas mixtures that alter metabolic demand or blood flow. The results suggest that BOLD contrast can be used to provide in vivo real-time maps of blood oxygenation in the brain under normal physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complements other techniques that are attempting to provide positron emission tomography-like measurements related to regional neural activity.
The investigation deals with the topography of principal sulci and of the temporal lobe within the international 10-20 system for electrode placement. Using magnetic resonance imaging in 16 healthy volunteers, the location and variability were studied for the superior central sulcus, the sylvian fissure, the calcarine sulcus and the anterobasal temporal lobe. Variation zones for these structures within the reference system are described. Craniocerebral variability was most pronounced in the areas remote from the relatively constant central and lateral sylvian region.
The technique of near-infra-red spectroscopy allows safe continuous monitoring of changes in blood and tissue oxygenation
on an intact organ. This is made possible by observing spectral changes in the tissues caused by oxygenated haemoglobin [HbO2], deoxygenated haemoglobin [Hb] and cytochrome aa3 [Cyt aa3]. The paper describes the design and performance of an instrument that has been developed to apply this technique to the
monitoring of the brain in newborn infants. The instrument monitors optical transmission changes across a newborn infant's
brain at four wavelengths. A standard deviation in error of 1 per cent (0·01 optical density OD) is achieved on measurements
of transmission changes at 20s intervals. This performance is obtained at a mean attenuation of 10 OD, the approximate attenuation
across a term infant's head. Long-term monitoring is possible as instrumental drift is less than 0·004 OD per hour.
Non invasive infrared spectroscopy is a well established technique for monitoring changes in the oxygenation status of tissues (1). The technique has in particular been successfully employed to monitor changes in cerebral blood and tissue oxygenation by observing the absorption of haemoglobin and cytochrome aa3 respectively. Because of the highly light scattering nature of the tissues studied, it has normally not been possible to quantitate the observed changes.
We studied the time course and magnitude of cerebral blood flow velocity (CBFV) changes in the middle cerebral artery (MCA) and the regional cerebral blood flow (rCBF) in the MCA territory during stimulation of the left sensorimotor cortex. Healthy right-handed male subjects were examined during performance of right-hand finger movement sequences, vibratory stimulation, and somatosensory discrimination. In somatosensory discrimination there were significant increases of the mean CBFV (4.8 +/- 9.9 cm/s; P < 0.01) and the mean rCBF (10.2 +/- 4.2 ml.100 g-1.min-1; P < 0.01), whereas no significant changes of the mean CBFV and rCBF occurred in finger movement sequences or vibratory stimulation. During all stimulation sessions the mean CBFV changes increased rapidly and reached a first maximum 3.3 +/- 0.3 s after stimulation onset. Simultaneous measurements of relative mean CBFV changes in both MCAs revealed left-right differences during voluntary finger movement sequences (left MCA, 14.3 +/- 10.6%; right MCA, 0.9 +/- 11.6%; P < 0.001) corresponding to a higher mean rCBF change in the left MCA territory. In the two tasks involving finger movements there was an increase of the respiratory rates (4.3 +/- 3.8 breaths/min; P < 0.05) and the pulse rates (11.6 +/- 5.5 beats/min; P < 0.05), respectively. Our data demonstrate a correspondence of mean CBFV and rCBF changes evoked by sensorimotor activation in the human brain. Furthermore, cerebral hemodynamic changes related to motor activity are accompanied by cardiorespiratory effects.
Stimulus-related signal changes in functional MRI of human brain activation not only reflect associated adjustments of cerebral blood flow and oxygen consumption, but strongly depend on the MRI technique chosen and the actual experimental setting. A list of relevant parameters includes static field homogeneity of the magnet, MR pulse sequence and signal type, TE, TR, flip angle, gradient strengths, gradient waveforms, receiver bandwidth and voxel size. In principle, a local signal increase during functional activation may reflect a regional change in cerebral blood flow or deoxyhemoglobin concentration or both. This ambiguity was demonstrated using long TE FLASH MRI at high spatial resolution. Subsequently, experimental strategies were evaluated that either discriminate MRI effects in large vessels from those in the cortical microvasculature or separate changes in blood flow velocity from those in blood oxygenation. Examples comprise studies of the human visual and motor cortex.
In healthy human adults, cerebral concentrations of oxygenated hemoglobin ([HbO2]) and deoxygenated hemoglobin ([HbR]) were assessed during brain activation using near infrared spectroscopy (NIRS). Measurements were made either in the frontal cortex (n = 10) during performance of cognitive tasks or in the occipital cortex (n = 6) during visual stimulation (flash-light exposure, picture observation). The typical findings during brain activation were an increase in [HbO2] and a decrease in [HbR]. We demonstrate that these findings are not due to alterations in skin blood flow. NIRS is a simple bedside technique for the assessment of hemodynamic alterations accompanying brain activation.
Image processing strategies for functional magnetic resonance imaging (FMRI) data sets acquired using a gradient-recalled echo-planar imaging sequence are considered. The analysis is carried out using the mathematics of vector spaces. Data sets consisting of N sequential images of the same slice of brain tissue are analyzed in the time-domain and also, after Fourier transformation, in the frequency domain. A technique for thresholding is introduced that uses the shape of the response in a pixel compared with the shape of a reference waveform as the decision criterion. A method is presented to eliminate drifts in data that arise from subject movement. The methods are applied to experimental FMRI data from the motor-cortex and compared with more conventional image-subtraction methods. Several finger motion paradigms are considered in the context of the various image processing strategies. The most effective method for image processing involves thresholding by shape as characterized by the correlation coefficient of the data with respect to a reference waveform followed by formation of a cross-correlation image. Emphasis is placed not only on image formation, but also on the use of signal processing techniques to characterize the temporal response of the brain to the paradigm.
Functional activation maps of the human visual cortex were obtained at a spatial resolution almost two orders of magnitude better than achievable by positron emission tomography and within measuring times of a few seconds. Transient alterations in the concentration of paramagnetic deoxyhemoglobin were conveniently detected at 2.0-T with use of RF-spoiled FLASH MRI sequences employing gradient echo times of 6 to 60 ms and voxel sizes of 2.5 to 39 microliters.
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