Neurofeedback Using Real-Time Near-Infrared Spectroscopy Enhances Motor Imagery Related Cortical Activation

Accumulating evidence indicates that motor imagery and motor execution share common neural networks. Accordingly, mental practices in the form of motor imagery have been implemented in rehabilitation regimes of stroke patients with favorable results. Because direct monitoring of motor imagery is difficult, feedback of cortical activities related to motor imagery (neurofeedback) could help to enhance efficacy of mental practice with motor imagery. To determine the feasibility and efficacy of a real-time neurofeedback system mediated by near-infrared spectroscopy (NIRS), two separate experiments were performed. Experiment 1 was used in five subjects to evaluate whether real-time cortical oxygenated hemoglobin signal feedback during a motor execution task correlated with reference hemoglobin signals computed off-line. Results demonstrated that the NIRS-mediated neurofeedback system reliably detected oxygenated hemoglobin signal changes in real-time. In Experiment 2, 21 subjects performed motor imagery of finger movements with feedback from relevant cortical signals and irrelevant sham signals. Real neurofeedback induced significantly greater activation of the contralateral premotor cortex and greater self-assessment scores for kinesthetic motor imagery compared with sham feedback. These findings suggested the feasibility and potential effectiveness of a NIRS-mediated real-time neurofeedback system on performance of kinesthetic motor imagery. However, these results warrant further clinical trials to determine whether this system could enhance the effects of mental practice in stroke patients

Can time-resolved NIRS provide the sensitivity to detect brain activity during motor imagery consistently?

Previous functional magnetic resonance imaging (fMRI) studies have shown that a subgroup of patients diagnosed as being in a vegetative state are aware and able to communicate by performing a motor imagery task in response to commands. Due to the fMRI\u27s cost and accessibility, there is a need for exploring different imaging modalities that can be used at the bedside. A promising technique is functional near infrared spectroscopy (fNIRS) that has been successfully applied to measure brain oxygenation in humans. Due to the limited depth sensitivity of continuous-wave NIRS, time-resolved (TR) detection has been proposed as a way of enhancing the sensitivity to the brain, since late arriving photons have a higher probability of reaching the brain. The goal of this study was to assess the feasibility and sensitivity of TR fNIRS in detecting brain activity during motor imagery. Fifteen healthy subjects were recruited in this study, and the fNIRS results were validated using fMRI. The change in the statistical moments of the distribution of times of flight (number of photons, mean time of flight and variance) were calculated for each channel to determine the presence of brain activity. The results indicate up to an 86% agreement between fMRI and TR-fNIRS and the sensitivity ranging from 64 to 93% with the highest value determined for the mean time of flight. These promising results highlight the potential of TR-fNIRS as a portable brain computer interface for patients with disorder of consciousness

Testing the potential of a virtual reality neurorehabilitation system during performance of observation, imagery and imitation of motor actions recorded by wireless functional near-infrared spectroscopy (fNIRS)

Background Several neurorehabilitation strategies have been introduced over the last decade based on the so-called simulation hypothesis. This hypothesis states that a neural network located in primary and secondary motor areas is activated not only during overt motor execution, but also during observation or imagery of the same motor action. Based on this hypothesis, we investigated the combination of a virtual reality (VR) based neurorehabilitation system together with a wireless functional near infrared spectroscopy (fNIRS) instrument. This combination is particularly appealing from a rehabilitation perspective as it may allow minimally constrained monitoring during neurorehabilitative training. Methods fNIRS was applied over F3 of healthy subjects during task performance in a virtual reality (VR) environment: 1) 'unilateral' group (N = 15), contralateral recording during observation, motor imagery, observation & motor imagery, and imitation of a grasping task performed by a virtual limb (first-person perspective view) using the right hand; 2) 'bilateral' group (N = 8), bilateral recording during observation and imitation of the same task using the right and left hand alternately. Results In the unilateral group, significant within-condition oxy-hemoglobin concentration Δ[O2Hb] changes (mean ± SD μmol/l) were found for motor imagery (0.0868 ± 0.5201 μmol/l) and imitation (0.1715 ± 0.4567 μmol/l). In addition, the bilateral group showed a significant within-condition Δ[O2Hb] change for observation (0.0924 ± 0.3369 μmol/l) as well as between-conditions with lower Δ[O2Hb] amplitudes during observation compared to imitation, especially in the ipsilateral hemisphere (p < 0.001). Further, in the bilateral group, imitation using the non-dominant (left) hand resulted in larger Δ[O2Hb] changes in both the ipsi- and contralateral hemispheres as compared to using the dominant (right) hand. Conclusions This study shows that our combined VR-fNIRS based neurorehabilitation system can activate the action-observation system as described by the simulation hypothesis during performance of observation, motor imagery and imitation of hand actions elicited by a VR environment. Further, in accordance with previous studies, the findings of this study revealed that both inter-subject variability and handedness need to be taken into account when recording in untrained subjects. These findings are of relevance for demonstrating the potential of the VR-fNIRS instrument in neurofeedback applications

VALIDATION OF A MODEL OF SENSORIMOTOR INTEGRATION WITH CLINICAL BENEFITS

Healthy sensorimotor integration – or how our touch influences our movements – is critical to efficiently interact with our environment. Yet, many aspects of this process are still poorly understood. Importantly, several movement disorders are often considered as originating from purely motor impairments, while a sensory origin could also lead to a similar set of symptoms. To alleviate these issues, we hereby propose a novel biologically-based model of the sensorimotor loop, known as the SMILE model. After describing both the functional, and the corresponding neuroanatomical versions of the SMILE, we tested several aspects of its motor component through functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS). Both experimental studies resulted in coherent outcomes with respect to the SMILE predictions, but they also provided novel scientific outcomes about such broad topics as the sub-phases of motor imagery, the neural processing of bodily representations, or the extend of the role of the extrastriate body area. In the final sections of this manuscript, we describe some potential clinical application of the SMILE. The first one presents the identification of plausible neuroanatomical origins for focal hand dystonia, a yet poorly understood sensorimotor disorder. The last chapter then covers possible improvements on brain-machine interfaces, driven by a better understanding of the sensorimotor system. -- La façon dont votre sens du toucher et vos mouvements interagissent est connue sous le nom d’intégration sensorimotrice. Ce procédé est essentiel pour une interaction normale avec tout ce qui nous entoure. Cependant, plusieurs aspects de ce processus sont encore méconnus. Plus important encore, l’origine de certaines déficiences motrices encore trop peu comprises sont parfois considérées comme purement motrice, alors qu’une origine sensorielle pourrait mener à un même ensemble de symptômes. Afin d’améliorer cette situation, nous proposons ici un nouveau modèle d’intégration sensorimotrice, dénommé « SMILE », basé sur les connaissances de neurobiologie actuelles. Dans ce manuscrit, nous commençons par décrire les caractéristiques fonctionnelles et neuroanatomiques du SMILE. Plusieurs expériences sont ensuite effectuées, via l’imagerie par résonance magnétique fonctionnelle (IRMf), et la stimulation magnétique transcranienne (SMT), afin de tester différents aspects de la composante motrice du SMILE. Si les résultats de ces expériences corroborent les prédictions du SMILE, elles ont aussi mis en évidences d’autres résultats scientifiques intéressants et novateurs, dans des domaines aussi divers que les sous-phases de l’imagination motrice, les processus cérébraux liés aux représentations corporelles, ou encore l’extension du rôle de l’extrastriate body area. Dans les dernières parties de ce manuscrit, nous dévoilons quelques applications cliniques potentielles de notre modèle. Nous utilisons le SMILE afin de proposer deux origines cérébrales plausibles de la dystonie focale de la main. Le dernier chapitre présente comment certaines technologies existantes, telles que les interfaces cerveaux-machines, pourraient bénéficier d’une meilleure compréhension du système sensorimoteur

Towards simultaneous electroencephalography and functional near-infrared spectroscopy for improving diagnostic accuracy in prolonged disorders of consciousness: a healthy cohort study

Qualitative clinical assessments of the recovery of awareness after severe brain injury require an assessor to differentiate purposeful behaviour from spontaneous behaviour. As many such behaviours are minimal and inconsistent, behavioural assessments are susceptible to diagnostic errors. Advanced neuroimaging tools such as functional magnetic resonance imaging and electroencephalography (EEG) can bypass behavioural responsiveness and reveal evidence of covert awareness and cognition within the brains of some patients, thus providing a means for more accurate diagnoses, more accurate prognoses, and, in some instances, facilitated communication. As each individual neuroimaging method has its own advantages and disadvantages (e.g., signal resolution, accessibility, etc.), this thesis studies on healthy individuals a burgeoning technique of non-invasive electrical and optical neuroimaging—simultaneous EEG and functional near-infrared spectroscopy (fNIRS)—that can be applied at the bedside. Measuring reliable covert behaviours is correlated with participant engagement, instrumental sensitivity and the accurate localisation of responses, aspects which are further addressed over three studies. Experiment 1 quantifies the typical EEG changes in response to covert commands in the absence and presence of an object. This is investigated to determine whether a goal-directed task can yield greater EEG control accuracy over simple monotonous imagined single-joint actions. Experiment 2 characterises frequency domain NIRS changes in response to overt and covert hand movements. A method for reconstructing haemodynamics using the less frequently investigated phase parameter is outlined and the impact of noise contaminated NIRS measurements are discussed. Furthermore, classification performances between frequency-domain and continuous-wave-like signals are compared. Experiment 3 lastly applies these techniques to determine the potential of simultaneous EEG-fNIRS classification. Here a sparse channel montage that would ultimately favour clinical utility is used to demonstrate whether such a hybrid method containing rich spatial and temporal information can improve the classification of covert responses in comparison to unimodal classification of signals. The findings and discussions presented within this thesis identify a direction for future research in order to more accurately translate the brain state of patients with a prolonged disorder of consciousness

Detecting Command-Driven Brain Activity in Patients with Disorders of Consciousness Using TR-fNIRS

Vegetative state (VS) is a disorder of consciousness often referred to as “wakefulness without awareness”. Patients in this condition experience normal sleep-wake cycles, but lack all awareness of themselves and their surroundings. Clinically, assessing consciousness relies on behavioural tests to determine a patient’s ability to follow commands. This subjective approach often leads to a high rate of misdiagnosis (~40%) where patients who retain residual awareness are misdiagnosed as being in a VS. Recently, functional neuroimaging techniques such as functional magnetic resonance imaging (fMRI), has allowed researchers to use command-driven brain activity to infer consciousness. Although promising, the cost and accessibility of fMRI hinder its use for frequent examinations. Functional near-infrared spectroscopy (fNIRS) is an emerging optical technology that is a promising alternative to fMRI. The technology is safe, portable and inexpensive allowing for true bedside assessment of brain function. This thesis focuses on using time-resolved (TR) fNIRS, a variant of fNIRS with enhanced sensitivity to the brain, to detect brain function in healthy controls and patients with disorders of consciousness (DOC). Motor imagery (MI) was used to assess command-driven brain activity since this task has been extensively validated with fMRI. The feasibility of TR-fNIRS to detect MI activity was first assessed on healthy controls and fMRI was used for validation. The results revealed excellent agreement between the two techniques with an overall sensitivity of 93% in comparison to fMRI. Following these promising results, TR-fNIRS was used for rudimentary mental communication by using MI as affirmation to questions. Testing this approach on healthy controls revealed an overall accuracy of 76%. More interestingly, the same approach was used to communicate with a locked-in patient under intensive care. The patient had residual eye movement, which provided a unique opportunity to confirm the fNIRS results. The TR-fNIRS results were in full agreement with the eye responses, demonstrating for the first time the ability of fNIRS to communicate with a patient without prior training. Finally, this approach was used to assess awareness in DOC patients, revealing residual brain function in two patients who had also previously shown significant MI activity with fMRI

A handy project : owning, perceiving, and experiencing hands

The purpose of this thesis is to explore the mental representation of hands in the context of owning, perceiving, and experiencing hands. The theoretical knowledge of the thesis is discussed in the first chapter, considering the wider concept of body representation. The second chapter reports the data from a study exploring the relationship between the sense of ownership of hands and motor control. The kinematic features of participants’ hands' movements were recorded using a motion analysis capture system and the associated brain activity was recorded using a near-infrared-spectroscopy device. Thirty-two healthy individuals participated in the study. The data show that the embodiment of a rubber hand through touch without vision does not influence the planning and execution of grasping actions (kinematic and brain imaging data). The third chapter presents a study exploring the influence of disgust on the mental representation of hands and feet in action, or motor imagery (MI). Thirty-six healthy individuals were enrolled (different participants from the study in chapter two). The data show that disgust enhances performance on MI tasks. The fourth chapter further expands the knowledge of hands-related MI abilities by comparing hand-based and foot-based MI tasks on a more implicit and explicit level (i.e. action monitoring required to solve the task). Fifty-five healthy participants participated in the data collection (different participants from the study in chapter three). Data show how differences in the mental representation of hands and feet in action imagery are specific to the degree of monitoring required, occurring only when the task is implicit; in other words, when the degree of action monitoring decreases. In the fifth chapter, a comparison between the data obtained in MI tasks executed in laboratory-based and online-based settings is presented, as the pandemic led to the opportunity to explore this aspect. This comparison shows comparable results between settings. Finally, in the sixth chapter, a general discussion of the thesis is presented, reasoning on the limitations of the various experiments and their impact. With the current thesis, I further expand the knowledge on the mental representation of hands, also considering feet as opposite body districts to hands. More in detail, my findings highlight i) that the application of the somatic RHI does not influence motion planning and execution (i.e. maximum GA) (owning hands), ii) that disgust influences our ability to mentally rotate hands and feet (perceiving hands), iii) and that the mental representation of hands and feet in action presents differences specific to the degree of action monitoring involved in solving the task (experiencing hands). The mental representation of hands is dynamic and can be influenced differently by different factors

Effects of Changes in Colored Light on Brain and Calf Muscle Blood Concentration and Oxygenation

Color light therapy is a therapeutic method in complementary medicine. In color therapy, light of two contrasting colors is often applied in a sequential order. The aim of this study was to investigate possible physiological effects, i.e., changes in the blood volume and oxygenation in the brain and calf muscle of healthy subjects who were exposed to red and blue light in sequential order. The hypothesis was that if a subject is first exposed to blue and then red light, the effect of the red light will be enhanced due to the contrastingly different characteristics of the two colors. The same was expected for blue light, if first exposing a subject to red and then to blue light. Twelve healthy volunteers (six male, six female) were measured twice on two different days by near-infrared spectroscopy during exposure to colored light. Two sequences of colored light were applied in a controlled, randomized, crossover design: first blue, then red, and vice versa. For the brain and muscle, the results showed no significant differences in blood volume and oxygenation between the two sequences, and a high interindividual physiological variability. Thus, the hypothesis had to be rejected. Comparing these data to results from a previous study, where subjects were exposed to blue and red light without sequential color changes, shows that the results of the current study appear to be similar to those of red light exposure. This may indicate that the exposure to red light was preponderant and thus effects of blue light were outweighed. KEYWORDS: color, color light therapy, near-infrared spectroscopy, NIRS, physiology, brain, muscle, hemodynamics, oxygenation functional study INTRODUCTION Light is essential for humankind. Although man has become fairly independent of Nature&apos;s day-and-night cycle, man still relies on light. Light influences human beings in many ways, on the physical, emotional, or spiritual-mental level. Light affects various physiological processes in man Colored light is also used in complementary medicine; however, no uniform concept exists, and forms and applications are manifold. Since it would extend the scope of this study to report in much detail on the various forms of colored light therapy, only general information is given. Colored light therapy is either used as stand-alone or within complementary medicine systems, such as anthroposophic medicine. The application of colored light in complementary medicine mostly aims at improving patients&apos; vitality and emotional and spiritual-mental well-being. Color light therapy is performed by either irradiating patients with colored light (direct application) or by facilitating patients to perceive colored light; for example, by projecting colored light onto a screen (indirect application). Although different concepts exist, it is common that the choice of the colors depends on the therapeutic goal; so-called warm colors (yellow, orange, and red) are applied to induce activating effects and so-called cool colors (cyan, blue, and violet) are applied to induce calm and relaxation. In practice, either single colors or combinations of colors are employed. When a combination is used, light of different colors is usually sequentially applied: green followed by red, or blue followed by red. While color light therapy has been used for many years, knowledge about possible effects of colored light and, in particular, its indirect application on physiological parameters is yet scarce. Therefore, the aim of our study was to investigate, using noninvasive near-infrared spectrophotometry (NIRS), the possible effects of blue and red light on blood volume and tissue oxygenation in the brain and calf muscle in healthy subjects. We focused on blue and red light as they are the two main colors used in medical treatment and hold opposite features as mentioned above. In a previous study, we investigated the effects of red and blue light severally Since colored light is often applied in sequential order, the aim of this study was to investigate the effects of red and blue light in a sequential order and, in particular, during the color changes. The hypothesis was that if a subject is first exposed to blue and then to red light, the effect of the red light will be enhanced due to the contrastingly different characteristics of the two colors. The same was expected for first exposing a subject to red and then to blue light. MATERIAL AND METHODS Study Design The study had a controlled, randomized (by computer), crossover design. Participants Thirteen healthy volunteers (seven male, six female) were measured during exposure to colored light. One male subject had to be excluded since he fell asleep during the measurement. The remaining twelve Weinzirl et al.: Colored Light and Brain Oxygenation TheScientificWorldJOURNAL (2011) 11, 1216-1225 1218 subjects had a mean age of 30 years, with a range of 18 to 44 years, mean height of 174 (159 to 190) cm, and mean weight of 65 (52 to 88) kg. Written informed consent was obtained prior to each measurement from all subjects. Material and Methods Light sources were white light bulbs (60W, OSRAM, Germany) incorporated in two arrays of 12 light bulbs each. Blue light filters were mounted in front of one-half of the light bulbs and red light filters (both filters, Lee, Germany) in front of the other half Measurement Protocol All subjects were measured twice on different days to avoid carryover effects. On the days of measurement, the subjects were exposed to the sequence of blue followed by red light or vice versa in a randomized, crossover protocol. Each subject was seated in a comfortable chair with armrests placed at a 1.5-m distance from a white wall One NIRS sensor was attached to the left forehead over the frontal lobe and at a location between Fp1 and F7 according to the international 10/20 system The protocol was approved by the Ethical Committee of the Canton of Basel, where the measurements were carried out due to logistic reasons and was in accordance with the Declaration of Helsinki. Measured Parameters Relative concentration changes of oxyhemoglobin (O 2 Hb in µM), deoxyhemoglobin (HHb in µM), total hemoglobin (tHb in µM), redox state of cytochrome oxidase aa3 (Cyt in µM), absolute values of total hemoglobin concentration (THI in µM, also called tissue hemoglobin index by the manufacturer), and tissue oxygen saturation (StO 2 in %, also named tissue oxygenation index [TOI] by the manufacturer) were measured in the frontal lobe of the brain and in the calf muscle throughout the entire experiment. While O 2 Hb, HHb, tHb, and Cyt were calculated using the modified Lambert-Beer law[27], the calculation of THI and StO 2 was based on spatially resolved spectroscopy StO 2 represents the regional tissue oxygenation, and is mainly related to changes in the arterial oxygen saturation and blood flow, and only weakly to changes in mean arterial blood pressure and cerebral blood volume Data Analysis The concentrations of O 2 Hb, HHb, tHb, Cyt, THI, and StO 2 were calculated by the software provided by the manufacturer (Hamamatsu Photonics, Hamamatsu, Japan). Data were manually screened for movement artifacts, which were removed. The first 3 min of the measurements were discarded because they may have contained initial transitions. The remaining 5 min of the baseline measurements were also tested for transition effects and since none were found, these 5 min constituted the initial baseline. Each measurement was divided into the following periods (5-min duration each): initial baseline, exposure to the first color, exposure to the second color, and three consecutive periods of recovery phase. For each of the periods, a median was calculated for each parameter and the values of the initial baseline were subtracted from the values of the other periods. Weinzirl et al.: Colored Light and Brain Oxygenation TheScientificWorldJOURNAL (2011) 11, 1216-1225 1220 Temporal changes: Using a paired t-test, the last 5-min period of the initial baseline was compared to the first and second period of the colored light exposure and to the three periods of recovery for each sequence (blue/red and red/blue) separately. In addition, the difference between the red and blue exposure for each sequence was analyzed by a t-test. Comparison of the two color sequences: Using a paired t-test, the values for the two sequences (blue/red and red/blue) were compared. Other parameters: By a linear mixed effects (LME) model (R statistical software), the influence of physiological parameters, such as age, weight, and height, on the measured parameters was tested. RESULTS Changes in Hemodynamics and Tissue Oxygenation in the Brain Temporal changes: The changes in the different parameters in the brain during and after exposure to blue/red and red/blue light are shown in Comparison of the two color sequences: Although the O 2 Hb and tHb traces appear different between the two sequences in Changes in Hemodynamics and Tissue Oxygenation Saturation of the Calf Muscle Temporal changes: In the calf muscle, O 2 Hb, tHb, THI, and, to a lesser extent, HHb concentration increased significantly during and after exposure for both sequences of blue/red and red/blue light DISCUSSION Changes in the Brain Although the O 2 Hb and tHb traces appear different between the two color sequences in To interpret the observed changes, they are best compared to the previous experiments, which focused on exposure to light of single colors without sequential color changes In the current study, there were no significant changes in any of the parameters (except Cyt) during and after the exposure, independent of the sequence (blue/red or red/blue). Thus, these changes are comparable to the changes in the previous study during red light exposure and different from the ones during blue light exposure. This could be interpreted as a preponderance of the effects excited by the red light over the effect of the blue light. This may be due to an outweighing effect of the red light or a too short exposure time (5 min) for the blue light to induce effects. Additionally, subjects were aware that after the blue light, the red light would appear. It is known from studies on the motor cortex that anticipating The significant decrease in the redox state of Cyt (red/blue sequence only) may be interpreted as a decrease in oxygenation, oxygen consumption, or blood flow. Despite its significance, the change was very small. It is noteworthy that tHb and THI seem to move in opposite directions even though the differences are not significant. This may indicate that the superficial tissue and the brain react in a differing way to the exposure to colored light. Consequently, our hypothesis that the contrast between the two colors will enhance the effect of one of the colors is rejected. Nonetheless, the results indicate a predominating effect of the red light. Weinzirl et al.: Colored Light and Brain Oxygenation TheScientificWorldJOURNAL (2011) 11, 1216-1225 1223 Changes in the Calf Muscle Again, for an easier understanding, we first summarize the findings of the previous publication In the current study, the tHb, O 2 Hb, and THI increased highly significantly for both sequences (blue/red and red/blue). Similar to the previous study, this can be explained by an accumulation of venous blood due to the sedentary position of the subjects during the measurement. The hypothesis of venous pooling is also supported by the slightly, although not significantly, decreased StO 2 . The results of the current study are similar to the exposure to solely red light in the previous study, while the significant increase in StO 2 during exposure to solely blue light is absent. Again this may be due to an outweighing effect of the red light or a too short exposure time (5 min) for the blue light to induce an effect. In summary, it appears that the effects excited by the red light exposure are dominant and outweigh the effects of the blue light. As for the brain, our hypothesis that the contrast between the two colors will enhance the effect of one of the colors is rejected. Nonetheless, the results suggest a preponderant effect of the red light. General Considerations, Limitations, and Outlook The statistical significance of p = 0.05 means per definition that one out of 20 tests will lead to statistical significance by pure chance, which holds true for any study with this significance level. Thus, if, as in this study, several statistical tests are carried out, it has to be considered that in 5% of the tests, significances may be obtained just by chance. The LME model (R statistical software) already takes into account multiple testing and therefore corrects for it. For the paired t-test, five tests were carried per parameter. As usual for exploratory studies, we did not correct for multiple testing. For example, for the time evolution, a Bonferroni correction could be applied, which means that the significance level should be set at p = 0.01 instead of p = 0.05. In this study, a correction for multiple testing has no relevant effect on the interpretation of the results because few, but mostly high, significances were found NIRS was used because it is completely noninvasive, does not use ionizing radiation or tracers, is compatible with other methods since it does not interfere electromagnetically (e.g., MRI, EEG) It would be worthwhile to include different aspects of exposure to colored light in future studies, e.g., different colors, intensities, durations, as well as other measurement locations and postures

Issues in the processing and analysis of functional NIRS imaging and a contrast with fMRI findings in a study of sensorimotor deactivation and connectivity

Includes abstract.~Includes bibliographical references.The first part of this thesis examines issues in the processing and analysis of continuous wave functional linear infrared spectroscopy (fNIRS) of the brain usung the DYNOT system. In the second part, the same sensorimotor experiment is carried out using functional magnetic resonance imaging (fMRI) and near infrared spectroscopy in eleven of the same subjects, to establish whether similar results can be obtained at the group level with each modality. Various techniques for motion artefact removal in fNIRS are compared. Imaging channels with negligible distance between source and detector are used to detect subject motion, and in data sets containing deliberate motion artefacts, independent component analysis and multiple-channel regression are found to improve the signal-to-noise ratio