Functional near-infrared spectroscopy in non-invasive neuromodulation

Non-invasive cerebral neuromodulation technologies are essential for the reorganization of cerebral neural networks,which have been widely applied in the field of central neurological diseases,such as stroke,Parkinson’s disease,and mental disorders.Although significant advances have been made in neuromodulation technologies,the identification of optimal neurostimulation paramete rs including the co rtical target,duration,and inhibition or excitation pattern is still limited due to the lack of guidance for neural circuits.Moreove r,the neural mechanism unde rlying neuromodulation for improved behavioral performance remains poorly understood.Recently,advancements in neuroimaging have provided insight into neuromodulation techniques.Functional near-infrared spectroscopy,as a novel non-invasive optical brain imaging method,can detect brain activity by measuring cerebral hemodynamics with the advantages of portability,high motion tole rance,and anti-electromagnetic interference.Coupling functional near-infra red spectroscopy with neuromodulation technologies offe rs an opportunity to monitor the cortical response,provide realtime feedbac k,and establish a closed-loop strategy integrating evaluation,feedbac k,and intervention for neurostimulation,which provides a theoretical basis for development of individualized precise neuro rehabilitation.We aimed to summarize the advantages of functional near-infra red spectroscopy and provide an ove rview of the current research on functional near-infrared spectroscopy in transcranial magnetic stimulation,transcranial electrical stimulation,neurofeedback,and braincomputer interfaces.Furthermore,the future perspectives and directions for the application of functional near-infrared spectroscopy in neuromodulation are summarized.In conclusion,functional near-infrared spectroscopy combined with neuromodulation may promote the optimization of central pellral reorganization to achieve better functional recovery form central nervous system diseases.

Cortical activity in patients with high-functioning ischemic stroke during the Purdue Pegboard Test:insights into bimanual coordinated fine motor skills with functional near-infrared spectroscopy

After stroke,even high-functioning individuals may experience compromised bimanual coordination and fine motor dexterity,leading to reduced functional independence.Bilateral arm training has been proposed as a promising intervention to address these deficits.However,the neural basis of the impairment of functional fine motor skills and their relationship to bimanual coordination performance in stroke patients remains unclear,limiting the development of more targeted interventions.To address this gap,our study employed functional near-infrared spectroscopy to investigate cortical responses in patients after stroke as they perform functional tasks that engage fine motor control and coordination.Twenty-four high-functioning patients with ischemic stroke(7 women,17 men;mean age 64.75±10.84 years)participated in this cross-sectional observational study and completed four subtasks from the Purdue Pegboard Test,which measures unimanual and bimanual finger and hand dexterity.We found significant bilateral activation of the sensorimotor cortices during all Purdue Pegboard Test subtasks,with bimanual tasks inducing higher cortical activation than the assembly subtask.Importantly,patients with better bimanual coordination exhibited lower cortical activation during the other three Purdue Pegboard Test subtasks.Notably,the observed neural response patterns varied depending on the specific subtask.In the unaffected hand task,the differences were primarily observed in the ipsilesional hemisphere.In contrast,the bilateral sensorimotor cortices and the contralesional hemisphere played a more prominent role in the bimanual task and assembly task,respectively.While significant correlations were found between cortical activation and unimanual tasks,no significant correlations were observed with bimanual tasks.This study provides insights into the neural basis of bimanual coordination and fine motor skills in high-functioning patients after stroke,highlighting task-dependent neural responses.The findings also suggest that patients who exhibit better bimanual performance demonstrate more efficient cortical activation.Therefore,incorporating bilateral arm training in post-stroke rehabilitation is important for better outcomes.The combination of functional near-infrared spectroscopy with functional motor paradigms is valuable for assessing skills and developing targeted interventions in stroke rehabilitation.

Synchronous measurements of prefrontal activity and pulse rate variability during online video game playing with functional near-infrared spectroscopy

Interactions between the central nervous system(CNS)and autonomic nervous system(ANS)play a crucial role in modulating perception,cognition,and emotion production.Previous studies on CNS–ANS interactions,or heart–brain coupling,have often used heart rate variability(HRV)metrics derived from electrocardiography(ECG)recordings as empirical measurements of sympathetic and parasympathetic activities.Functional near-infrared spectroscopy(fNIRS)is a functional brain imaging modality that is increasingly used in brain and cognition studies.The fNIRS signals contain frequency bands representing both neural activity oscillations and heartbeat rhythms.Therefore,fNIRS data acquired in neuroimaging studies can potentially provide a single-modality approach to measure task-induced responses in the brain and ANS synchronously,allowing analysis of CNS–ANS interactions.In this proof-of-concept study,fNIRS was used to record hemodynamic changes from the foreheads of 20 university students as they each played a round of multiplayer online battle arena(MOBA)game.From the fNIRS recordings,neural and heartbeat frequency bands were extracted to assess prefrontal activities and shortterm pulse rate variability(PRV),an approximation for short-term HRV,respectively.Under the experimental conditions used,fNIRS-derived PRV metrics showed good correlations with ECG-derived HRV golden standards,in terms of absolute measurements and video game playing(VGP)-related changes.It was also observed that,similar to previous studies on physical activity and exercise,the PRV metrics closely related to parasympathetic activities recovered slower than the PRV indicators of sympathetic activities after VGP.It is concluded that it is feasible to use fNIRS to monitor concurrent brain and ANS activations during online VGP,facilitating the understanding of VGP-related heart–brain coupling.

Correlation between LIFG and Autonomic Activation during Stressful Tasks:A Functional Near-infrared Spectroscopy (fNIRS) Study

It remains unclear whether language tasks in one＇s first （L1） or second （L2） language can cause stress responses and whether frontal, autonomic and behavioral responses to stressful tasks are correlated. In this study, we studied 22 Chinese subjects whose L2 was English and measured the cerebral blood oxygenation in their frontal lobe by using functional near-infrared spectroscopy （fNIRS） as par- ticipants engaged in a mental arithmetic task （MAT） and verbal fluency tasks （VFTs） in L1 （Chinese） and L2 （English）. To examine the activated cortical areas, we estimated the channel location based on Montreal Neurological Institute （MNI） standard brain space by using a-probabilistic estimation method. We evaluated heart rate （HR） changes to analyze autonomic nervous system （ANS） functioning. We found that the MAT and VFTs induced greater increases in HR than did the control （Ctrl） task. Further- more, subjects developed greater increases in HR in the MAT and VFTt~ than they did in the VFTL1. Compared with the Ctrl task, the MAT and both VFTLland VFTL2 produced robust and widespread bi- lateral activation of the frontal cortex. Interestingly, partial correlation analysis indicated that the activity in the left inferior frontal gyrus （LIFG） [Brodmarm＇s area （BA） 47] was consistently correlated with the increases in HR across the three tasks （MAT, VFTL2, and VFTL1）, after controlling for the performance data. The present results suggested that a VFT in L2 may be more stressful than in L1. The LIFG may affect the activation of the sympathetic system induced by stressful tasks, includin~ MATs and VFTs.

Comparison of brain functions between healthy participants and methamphetamine users with various addiction histories:Data analysis based on EEG and fNIRS

The electroencephalogram(EEG)rhythm and functional near-infrared spectroscopy(fNIRS)activation levels have not been compared between a healthy control group(HCG)and methamphetamine user group(MUG)with different addiction histories.This study used 64-electrode EEG and fNIRS to conduct an experiment that analyzed the resting and craving states.The EEG and fNIRS data of 56 participants were collected,including 14 healthy participants,14 methamphetamine users with an addiction history of 0.5–5 years,14 users with an addiction history of 5–10 years,and 14 users with an addiction history of 10–15 years.Isolated effective coherence(iCoh)within the brain network was used to process the EEG data.Statistical analysis was performed to compare differences in iCoh among the delta,theta,alpha,beta,and gamma bands and explore oxyhemoglobin activation levels in the ventrolateral prefrontal cortex,dorsolateral prefrontal cortex,orbitofrontal cortex,and frontopolar prefrontal cortex(FPC)of the control group.Finally,the Kmeans,Gaussian mixed model(GMM),linear discriminant analysis(LDA),support vector machine(SVM),Bayes,and convolutional neural networks(CNN)algorithms were used to classify methamphetamine users based on drug and neutral images.A 3-class accuracy was achieved.Changes in EEG and fNIRS activation levels of HCG and MUG with varied addiction histories were demonstrated.

DISCRIMINATION OF MENTAL WORKLOAD LEVELS IN HUMAN SUBJECTS WITH FUNCTIONAL NEAR-INFRARED SPECTROSCOPY

We have applied functional near-infrared spectroscopy(fNIRS)to the human forehead to distinguish different levels of mental workload on the basis of hemodynamic changes occurring in the prefrontal cortex.We report data on 3 subjects from a protocol involving 3 mental workload levels based on to working memory tasks.To quantify the potential of fNIRS for mental workload discrimination,we have applied a 3-nearest neighbor classification algorithm based on the amplitude of oxyhemoglobin(HbO2)and deoxyhemoglobin(HbR)concentration changes associated with the working memory tasks.We have found classification success rates in the range of 44%-72%,which are significantly higher than the corresponding chance level(for random data)of 19.1%.This work shows the potential of fNIRS for mental workload classification,especially when more parameters(rather than just the amplitude of concentration changes used here)and more sophisticated classification algorithms(rather than the simple 3-nearest neighbor algorithm used here)are considered and optimized for this application.

ASSESSING WORKING MEMORY IN REAL-LIFE SITUATIONS WITH FUNCTIONAL NEAR-INFRARED SPECTROSCOPY

Working memory is one of the most important functions in our brain,which has been widely studied with unreal-life measured technologies.A functional near-infrared spectroscopy(fNIRS)instrument with a portable and low-cost design is developed,which is capable of providing hemodynamic measurement associated with brain function in real-life situations.Using this instrument,we performed working memory studies involved in Chinese words encoding,verbal,and spatial stem recognition,which are mainly studied with other technologies.Our results show that fNIRS can well assess working memory activities,in comparison with the reported results mainly using other methodologies.Furthermore,we find that hemodynamic change in the prefrontal cortex during all working memory tasks is highly associated with subjects’behavioral data.fNIRS is shown to be a promising alternative to the current methodologies for studying or assessing functional brain activities in natural condition.

DISCRIMINATIVE ANALYSIS OF FUNCTIONAL NEAR-INFRARED SPECTROSCOPY SIGNALS FOR DEVELOPMENT OF NEUROIMAGING BIOMARKERS OF ELDERLY DEPRESSION

Functional near-infrared spectroscopy(fNIRS)is a neuroimaging technology which is suitable for psychiatric patients.Several fNIRS studies have found abnormal brain activations during cognitive tasks in elderly depression.In this paper,we proposed a discriminative model of multivariate pattern classification based on fNIRS signals to distinguish elderly depressed patients from healthy controls.This model used the brain activation patterns during a verbal fluency task as features of classification.Then Pseudo-Fisher Linear Discriminant Analysis was performed on the feature space to generate discriminative model.Using leave-one-out(LOO)cross-validation,our results showed a correct classification rate of 88%.The discriminative model showed its ability to identify people with elderly depression and suggested that fNIRS may be an efficient clinical tool for diagnosis of depression.This study may provide the first step for the development of neuroimaging biomarkers based on fNIRS in psychiatric disorders.

Odorant discrimination using functional near-infrared spectroscopy of the main olfactory bulb in rats

We characterize the hemodynamic response changes in the main olfactory bulb(MOB)of anesthetized rats with near-infrared spectroscopy(NIRS)during the presentation of three different odorants:(i)plain air as a reference(Blank),(ii) 2-heptanone(HEP),and(iii)isopropylbenzene(Ib).Odorants generate different changes in the concentrations of oxyhemoglobin.Our results suggest that NIRS technology might be useful in discriminating various odorants in a non-invasive manner using animals with a superb olfactory system.

Right prefrontal cortex is activated for perceiving postural limits: a functional near-infrared spectroscopy study

The purpose of this study was to investigate neuronal mechanisms active during the percep-tion of forward postural limits in a standing po-sition and to specify fall-related brain activity using optical functional near-infrared spectros-copy. The study group included six right-handed, healthy female volunteers (range: 19, 20 years). The optical imaging device comprised 16 opto-des designed to provide 24-channel recording of changes in hemoglobin oxygenation. We meas-ured the changes of oxygenated hemoglobin levels in the frontal region when subjects per-ceived reachability in a standing position. Com- pared with those in other regions, the oxygen-ated hemoglobin levels in the right frontal region compatible with the right prefrontal cortex sig-nificantly increased. This result suggests that brain activities in the right prefrontal cortex are related to perception of reachability. Overesti-mation of postural limits has been reported as one of the risk factor for falling. This overesti-mation might be induced by dysfunction in the prefrontal cortex, resulting in a failure to inhibit a motor program that would have caused a loss of balance in reaching. Activation of the right prefrontal cortex may be a key factor for pre-venting accidental falls in the elderly and in pa-tients with neurological disorders.

Effect of head model on Monte Carlo modeling of spatial sensitivity distribution for functional near-infrared spectroscopy

Modeling Light propagation within human head to deduce spatial sensitivity distribution(SSD)is important for Near-infrared spectroscopy(NIRS)/imaging(NIRI)and diffuse correlation tomography.Lots of head models have been used on this issue,including layered head model,artificial simplified head model,MRI slices described head model,and visible human head model.Hereinto,visible Chinese human(VCH)head model is considered to be a most faithful presentation of anatomical structure,and has been highlighted to be employed in modeling light propagation.However,it is not practical for all researchers to use VCH head models and actually increasing number of people are using magnet resonance imaging(MRI)head models.Here,all the above head models were simulated and compared,and we focused on the effect of using di®erent head models on predictions of SSD.Our results were in line with the previous reports on the effect of cerebral cortex folding geometry.Moreover,the in fluence on SSD increases with thefidelity of head models.And surprisingly,the SSD percentages in scalp and gray matter(region of interest)in MRI head model were found to be 80%and 125%higher than in VCH head model.MRI head models induced nonignorable discrepancy in SSD estimation when compared with VCH head model.This study,as we believe,is the first to focus on comparison among full serials of head model on estimating SSD,and provided quantitative evidence for MRI head model users to calibrate their SSD estimation.

Functional near-infrared spectroscopy can detect low-frequency hemodynamic oscillations in the prefrontal cortex during steady-state visual evoked potentialinducing periodic facial expression stimuli presentation

Brain oscillations are vital to cognitive functions,while disrupted oscillatory activity is linked to various brain disorders.Although high-frequency neural oscillations(>1 Hz)have been extensively studied in cognition,the neural mechanisms underlying low-frequency hemodynamic oscillations(LFHO)<1 Hz have not yet been fully explored.One way to examine oscillatory neural dynamics is to use a facial expression(FE)paradigm to induce steady-state visual evoked potentials(SSVEPs),which has been used in electroencephalography studies of high-frequency brain oscillation activity.In this study,LFHO during SSVEP-inducing periodic flickering stimuli presentation were inspected using functional near-infrared spectroscopy(fNIRS),in which hemodynamic responses in the prefrontal cortex were recorded while participants were passively viewing dynamic FEs flickering at 0.2 Hz.The fast Fourier analysis results demonstrated that the power exhibited monochronic peaks at 0.2 Hz across all channels,indicating that the periodic events successfully elicited LFHO in the prefrontal cortex.More importantly,measurement of LFHO can effectively distinguish the brain activation difference between different cognitive conditions,with happy FE presentation showing greater LFHO power than neutral FE presentation.These results demonstrate that stimuli flashing at a given frequency can induce LFHO in the prefrontal cortex,which provides new insights into the cognitive mechanisms involved in slow oscillation.

基于线性映射场的fNIRS信号特征提取与分析

大脑功能性激活的相关研究普遍存在特征提取依赖人工经验、深层次生理学信息难以挖掘两大问题。针对这两个问题,该文通过引入变分模态分解(VMD)技术,提出自适应VMD算法。该算法考虑了脑血氧信号在不同频段下的生理意义,降低了传统VMD对超参数选取的依赖。实验结果表明自适应VMD算法能够精确地提取出功能性近红外光谱(fNIRS)中富有生理学意义的有效模态分量,进而提升数据预处理效果。在此基础上,基于将时间序列映射成图像并使用深度卷积神经网络进行特征学习的思路,提出线性映射场(LMF)。基于LMF,该文以较低的运算量将fNIRS序列映射成2维图像,辅以深度卷积神经网络,实现了fNIRS生理信号深层次特征的提取。实验结果证明了所提出LMF的优势。最后,该文对提出方法的有效性进行了讨论与分析,说明了不同于循环神经网络仅能“顺序”地感知时间序列,卷积神经网络对时间序列的“跳跃”感知是其取得优异效果的关键。

Motor network reorganization in stroke patients with dyskinesias during a shoulder-touching task:A fNIRS study

Hemiplegia after stroke has become a major cause of the world's high disabilities,and it is vital to enhance our understanding of post-stroke neuroplasticity to develop e±cient rehabilitation programs.This study aimed to explore the brain activation and network reorganization of the motor cortex(MC)with functional near-infrared spectroscopy(fNIRS).The MC hemodynamic signals were gained from 22 stroke patients and 14 healthy subjects during a shoulder-touching task with the right hand.The MC activation pattern and network attributes analyzed with the graph theory were compared between the two groups.The results revealed that healthy controls presented dominant activation in the left MC while stroke patients exhibited dominant activation in the bilateral hemispheres MC.The MC networks for the two groups had small-world properties.Compared with healthy controls,patients had higher transitivity and lower global e±ciency(GE),mean connectivity,and long connections(LCs)in the left MC.In addition,both MC activation and network attributes were correlated with patient's upper limb motor function.The results showed the stronger compensation of the unaffected motor area,the better recovery of the upper limb motor function for patients.Moreover,the MC network possessed high clustering and relatively sparse inter-regional connections during recovery for patients.Our results promote the understanding of MC reorganization during recovery and indicate that MC activation and network could provide clinical assessment signi¯cance in stroke patients.Given the advantages of fNIRS,it shows great application potential in the assessment and rehabilitation of motor function after stroke.

Near-infrared spectroscopy as a promising tool in stroke:Current applications and future perspectives

Stroke is caused by an acute focal disruption of the vasculature in the central nervous system.Neurological-related functional deficits are the most devastating consequences for stroke survi-vors.Neural signals from stroke patients can reflect the functional statuses of patients and provide insights into the neuronal recovery mechanism for functioning,which could be used as the basis for designing optimal treatment strategies.Near-infrared spectroscopy(NIRS)is a low-cost,noninvasive,easily operated neuroimage method and it is compatible with various rehabilitative programs.These advantages make NIRS an excellent candidate in research for stroke recovery.Here,we focused on the brain functions and recovery for stroke patients at stable status,conducted a systematic literature review about NIRS applications in stroke since 2000 and identified a total of 72 references through ScienceDirect and PubMed database retrieval.The NIRS studies in stroke include resting-state function and its recovery,motor function and itsrecovery,motor and cognition interference,cognitive function and its recovery,language function and its recovery,emotional function and its recovery and other applications.Based on the results of the quality assessment,we identified some study gaps from the previous research and provided suggestions for some methodological improvement in the future.The trend of NIRS gives a boost to its application in stroke,and the potential research directions for NIRS in stroke are pros-pected,including multi-center clinical research,treatment efficacy prediction research and brain-muscle coupling research.Finally,limitations of NIRS are discussed.

The Effects of Task Order Administration on Test Scores from the Trail Making Test: Near-Infrared Spectroscopy Investigations

This research examines the effects of task administration on Trail Making Test performance. The TMT consists of two parts, TMT Part A and TMT Part B. Generally, it has been believed that the order the two parts are completed does not influence test results;however, there is one previous study that has suggested that the order is indeed an influential factor on test scores. To measure frontal lobe function, the present study used near-infrared spectroscopy to measure changes in oxygenated hemoglobin (oxy-Hb) in 48 young, healthy Japanese subjects as they completed Parts A and B. We subtracted the change in oxy-Hb while completing Part A from that while completing Part B (B-A Oxy-Hb) for a comparison to facilitate an investigation of how, or if, the order in which the TMT is taken influences test success. We found that when Part A was completed first, there were only small changes in the B-A oxy-Hb, but when Part B was completed first, there were larger changes. This study indicates that the order the tests are completed in may influence outcomes, thus assessments using the TMT must follow a consistent task order.

A Preliminary Near-Infrared Spectroscopy Study in Adolescent and Adult Patients with Attention-Deficit/Hyperactivity Disorder Symptoms

Prefrontal dysfunction in patients with attention-deficit/hyperactivity disorder (AD/HD) has been repeatedly detected on a behavioral level, and various brain-imaging studies have elucidated the pathophysiology of AD/HD. Recent advances in near-infrared spectroscopy (NIRS) have enabled noninvasive investigations of brain function in various mental disorders, especially major depression, schizophrenia, and bipolar disorder. The objective of this preliminary study was to use NIRS to evaluate changes in frontal lobe blood flow in post childhood or adult patients with AD/HD symptoms. The subjects included five patients with a range of mental disorders and AD/HD symptoms, and a matched (age, sex, and dominant hand) control group of five healthy subjects. We compared the changes in cerebral blood flow during verbal fluency tasks between the two groups. The duration of the elevated oxygenated hemoglobin was notably shorter in the AD/HD group than that in the healthy control group. We suggest that the shorter elevation durations of oxygenated hemoglobin concentrations might be a biological indicator for post childhood or adult AD/HD or of impaired executive functioning.

脑功能成像的新方法——功能性近红外光谱技术(fNIRS)

功能性近红外光谱技术(functional near-infrared spectroscopy,fNIRS)利用血液的主要成分对600-900nm近红外光良好的散射性,从而获得大脑活动时氧合血红蛋白和脱氧血红蛋白的变化情况。目前该技术开始运用于自然情境下的高级认知、发展心理学、异常心理学等多个领域的研究。该技术具有造价较低、便携性好,无噪音、无创性和对实验过程中被试动作不会过份敏感等优点,但也存在空间分辨率不高和校正算法有待进一步完善等方面的不足。未来fNIRS的研究可以与fMRI等其他成像技术进行结合,开展婴幼儿和特殊人群的认知神经科学研究以及自然情境下大脑认知的神经机制研究。

基于fNIRS的运动执行与运动想象脑激活模式比较

使用《运动想象问卷-修订版》筛选出的30名被试(男女各半),采用功能性近红外光谱成像技术(fNIRS)监测被试在执行实际举哑铃(男生,4磅和8磅;女生,2磅和4磅)任务和想象举同等重量哑铃任务时,其大脑皮层氧合血红蛋白浓度的变化。结果发现:男女被试在运动执行与运动想象任务下都激活了主运动皮层;且运动执行的大脑激活水平高于运动想象。在执行实际运动任务时,运动强度显著影响大脑皮层血氧浓度的变化,表现出左半球偏侧化优势;在执行想象运动任务时,运动强度没有影响大脑皮层血氧浓度的变化,且无偏侧化现象。

基于功能近红外光谱技术(fNIRs)的帕金森病大鼠模型脑组织特性研究

利用功能近红外光谱技术(functionality near infrared spectroscopy,fNIRs)探索帕金森病(parkin-son′s disease,PD)大鼠模型的脑组织功能特性。通过小动物磁共振(magnetic resonance imaging,MRI)和电子计算机断层扫描(computed tomography,CT)对PD大鼠模型进行影像学研究,用fNIRs系统测试大鼠模型脑组织纹状体特征参数。实验结果表明,PD大鼠脑部没有明显的形态结构变化;优化散射系数(reducedscattering coefficient:μ′s)、脑血容量(cerebral blood volume:CBV)在PD大鼠的纹状体部与对照组间存在显著的差别;fNIRs测量参数(μ′s、CBV)与CT灌注(CTP)测定参数[CBF(cerebral blood flow),CBV]之间存在相关性。这些结果表明fNIRs可以作为PD研究的重要参考手段。