Functional near-infrared spectroscopy in movement science: a systematic review on cortical activity in postural and walking tasks

Cerebral and muscle tissue oxygenation during exercise in healthy adults: A systematic review

BACKGROUND

Near-infrared spectroscopy (NIRS) technology has allowed for the measurement of cerebral and skeletal muscle oxygenation simultaneously during exercise. Since this technology has been growing and is now successfully used in laboratory and sports settings, this systematic review aimed to synthesize the evidence and enhance an integrative understanding of blood flow adjustments and oxygen (O2) changes (i.e., the balance between O2 delivery and O2 consumption) within the cerebral and muscle systems during exercise.

METHODS

A systematic review was conducted using PubMed, Embase, Scopus, and Web of Science databases to search for relevant studies that simultaneously investigated cerebral and muscle hemodynamic changes using the near-infrared spectroscopy system during exercise. This review considered manuscripts written in English and available before February 9, 2023. Each step of screening involved evaluation by 2 independent authors, with disagreements resolved by a third author. The Joanna Briggs Institute Critical Appraisal Checklist was used to assess the methodological quality of the studies.

RESULTS

Twenty studies were included, of which 80% had good methodological quality, and involved 290 young or middle-aged adults. Different types of exercises were used to assess cerebral and muscle hemodynamic changes, such as cycling (n = 11), treadmill (n = 1), knee extension (n = 5), isometric contraction of biceps brachii (n = 3), and duet swim routines (n = 1). The cerebral hemodynamics analysis was focused on the frontal cortex (n = 20), while in the muscle, the analysis involved vastus lateralis (n = 18), gastrocnemius (n = 3), biceps brachii (n = 5), deltoid (n = 1), and intercostal muscle (n = 1). Overall, muscle deoxygenation increases during exercise, reaching a plateau in voluntary exhaustion, while in the brain, oxyhemoglobin concentration increases with exercise intensity, reaching a plateau or declining at the exhaustion point.

CONCLUSION

Muscle and cerebral oxygenation respond differently to exercise, with muscle increasing O2 utilization and cerebral tissue increasing O2 delivery during exercise. However, at the exhaustion point, both muscle and cerebral oxygenation become compromised. This is characterized by a reduction in blood flow and a decrease in O2 extraction in the muscle, while in the brain, oxygenation reaches a plateau or decline, potentially resulting in motor failure during exercise.

Mobile neuroimaging: What we have learned about the neural control of human walking, with an emphasis on EEG-based research

Our understanding of the neural control of human walking has changed significantly over the last twenty years and mobile brain imaging methods have contributed substantially to current knowledge. High-density electroencephalography (EEG) has the advantages of being lightweight and mobile while providing temporal resolution of brain changes within a gait cycle. Advances in EEG hardware and processing methods have led to a proliferation of research on the neural control of locomotion in neurologically intact adults. We provide a narrative review of the advantages and disadvantages of different mobile brain imaging methods, then summarize findings from mobile EEG studies quantifying electrocortical activity during human walking. Contrary to historical views on the neural control of locomotion, recent studies highlight the widespread involvement of many areas, such as the anterior cingulate, posterior parietal, prefrontal, premotor, sensorimotor, supplementary motor, and occipital cortices, that show active fluctuations in electrical power during walking. The electrocortical activity changes with speed, stability, perturbations, and gait adaptation. We end with a discussion on the next steps in mobile EEG research.

A scoping review of functional near-infrared spectroscopy biomarkers in late-life depression: Depressive symptoms, cognitive functioning, and social functioning

Late-life depression is one of the most damaging mental illnesses, disrupting the normal lives of older people by causing chronic illness and cognitive impairment. Patients with late-life depression, accompanied by changes in appetite, insomnia, fatigue and guilt, are more likely to experience irritability, anxiety and somatic symptoms. It increases the risk of suicide and dementia and is a major challenge for the public health systems. The current clinical assessment, identification and effectiveness assessment of late-life depression are primarily based on history taking, mental status examination and scale scoring, which lack subjectivity and precision. Functional near-infrared spectroscopy is a rapidly developing optical imaging technology that objectively reflects the oxygenation of hemoglobin in different cerebral regions during different tasks and assesses the functional status of the cerebral cortex. This article presents a comprehensive review of the assessment of functional near-infrared spectroscopy technology in assessing depressive symptoms, social functioning, and cognitive functioning in patients with late-life depression. The use of functional near-infrared spectroscopy provides greater insight into the neurobiological mechanisms underlying depression and helps to assess these three aspects of functionality in depressed patients. In addition, the study discusses the limitations of previous research and explores potential advances in the field.

Cortical Mechanisms Underlying Effects of Repetitive Peripheral Magnetic Stimulation on Dynamic and Static Postural Control in Patients with Chronic Non-Specific Low Back Pain: A Double-Blind Randomized Clinical Trial

INTRODUCTION

Patients with chronic non-specific low back pain (CNLBP) often experience impaired postural control, contributing to pain recurrence. Although repetitive peripheral magnetic stimulation (rPMS) combined with core muscle training (CMT) could improve postural control, its neural mechanism remains unclear. This study aims to investigate the postural control-related cortical mechanism of the effect of rPMS on patients with CNLBP.

METHODS

This unicentric, prospective, randomized, double-blind, controlled trial was conducted in a public hospital from May to December 2023. A total of 40 patients (27 females and 13 males, mean age 29.38 ± 7.72) with CNLBP were randomly assigned to either the rPMS group (real rPMS with CMT) or the sham-rPMS group (sham-rPMS with CMT) for 12 sessions over 4 weeks. The rPMS was applied to the lumbar paravertebral multifidus muscle on the painful side. Pain and disability were quantified using the visual analog scale (VAS) and Oswestry dysfunction index (ODI) pre- and post-intervention. Furthermore, the sway area and velocity of the center of pressure (COP) were measured using a force platform. The cortical activities in 6 regions of interest during 4 tasks (standing with eyes open/closed on a stable/unstable plane) were recorded by functional near-infrared spectroscopy (fNIRS) pre- and post-intervention. The repeated measure ANOVA was applied for statistical analysis. Spearman's correlation was used to determine the relationships between variables.

RESULTS

After the intervention, the rPMS group showed decreased pain intensity (p = 0.001) and sway area (unstable eyes-closed task) (p = 0.046) compared to the sham-rPMS group. Additionally, the rPMS group exhibited increased activation in left primary motor cortex (M1) (p = 0.042) and reduced in left supplementary motor area (SMA) (p = 0.045), whereas the sham-rPMS group showed no significant changes. The increased activation of left M1 was negatively correlated to the reduction of pain intensity (r = - 0.537, p = 0.018) and sway area (r = - 0.500, p = 0.029) under the static balancing task. Furthermore, there was a positive correlation between sway velocity and VAS (r = 0.451, p = 0.046) post-rPMS intervention.

CONCLUSION

Repetitive peripheral magnetic stimulation combined with core muscle training demonstrated better analgesic effects and postural control improvements, compared to sham-stimulation. This may be attributed to the increased activation of the left primary motor cortex.

CLINICAL TRIAL REGISTRATION

The trial was registered on ClinicalTrials.gov (ChiCTR2300070943).

Flexible-circuit-based 3-D aware modular optical brain imaging system for high-density measurements in natural settings

Significance

Functional near-infrared spectroscopy (fNIRS) presents an opportunity to study human brains in everyday activities and environments. However, achieving robust measurements under such dynamic condition remains a significant challenge.

Aim

The modular optical brain imaging (MOBI) system is designed to enhance optode-to-scalp coupling and provide real-time probe 3-D shape estimation to improve the use of fNIRS in everyday conditions.

Approach

The MOBI system utilizes a bendable and lightweight modular circuit-board design to enhance probe conformity to head surfaces and comfort for long-term wearability. Combined with automatic module connection recognition, the built-in orientation sensors on each module can be used to estimate optode 3-D positions in real-time to enable advanced tomographic data analysis and motion tracking.

Results

Optical characterization of the MOBI detector reports a noise equivalence power (NEP) of 8.9 and 7.3 pW / H z at 735 nm and 850 nm, respectively, with a dynamic range of 88 dB. The 3-D optode shape acquisition yields an average error of 4.2 mm across 25 optodes in a phantom test compared to positions acquired from a digitizer. Results for initial in vivo validations, including a cuff occlusion and a finger-tapping test, are also provided.

Conclusions

To the best of our knowledge, the MOBI system is the first modular fNIRS system featuring fully flexible circuit boards. The self-organizing module sensor network and automatic 3-D optode position acquisition, combined with lightweight modules (18 g/module) and ergonomic designs, would greatly aid emerging explorations of brain function in naturalistic settings.

Postural Control and Muscle Activity during Dual-Task in Young Adults

In everyday life, we recurrently perform two tasks simultaneously, which is called dual-tasking. A common dual task is smartphone use while standing or walking. According to previous studies, this task can compromise postural stability. However, few studies have analyzed lower limb muscle activity during dual-tasking using smartphones. This study aimed to assess the postural sway and muscle activity during dual-tasking in young adults. Thirty-six healthy young adults (23.08 ± 3.92 years) participated in this study. They performed a single task (ST: keeping a quiet standing posture) and a dual task (DT: keeping the ST while simultaneously performing a cognitive task on their smartphone). Postural sway was assessed through the center of pressure (CoP) analysis using a force platform: total CoP displacement, CoP displacement in the anterior-posterior and medial-lateral directions, mean total velocity of the CoP, mean velocity of the CoP in the anterior-posterior and medial-lateral directions, and 95% confidence ellipse sway area. A surface electromyography system recorded the muscle activity of the lumbar spinal erector and five muscles of the lower limb (bilaterally). The results showed an increase in postural sway from the ST to the DT in all CoP variables (p < 0.05), and muscle activity in most muscles analyzed decreased from the ST to the DT (p < 0.05). In conclusion, our results reflect a decentralization of attention from motor performance once postural sway increased and muscle activity decreased in dual-task conditions.

Prefrontal cortical activity during uneven terrain walking in younger and older adults

Introduction

Walking in complex environments increases the cognitive demand of locomotor control; however, our understanding of the neural mechanisms contributing to walking on uneven terrain is limited. We used a novel method for altering terrain unevenness on a treadmill to investigate the association between terrain unevenness and cortical activity in the prefrontal cortex, a region known to be involved in various cognitive functions.

Methods

Prefrontal cortical activity was measured with functional near infrared spectroscopy while participants walked on a novel custom-made terrain treadmill surface across four different terrains: flat, low, medium, and high levels of unevenness. The assessments were conducted in younger adults, older adults with better mobility function and older adults with worse mobility function. Mobility function was assessed using the Short Physical Performance Battery. The primary hypothesis was that increasing the unevenness of the terrain would result in greater prefrontal cortical activation in all groups. Secondary hypotheses were that heightened prefrontal cortical activation would be observed in the older groups relative to the younger group, and that prefrontal cortical activation would plateau at higher levels of terrain unevenness for the older adults with worse mobility function, as predicted by the Compensation Related Utilization of Neural Circuits Hypothesis.

Results

The results revealed a significant main effect of terrain, indicating a significant increase in prefrontal cortical activation with increasing terrain unevenness during walking in all groups. A significant main effect of group revealed that prefrontal cortical activation was higher in older adults with better mobility function compared to younger adults and older adults with worse mobility function in all pooled terrains, but there was no significant difference in prefrontal cortical activation between older adults with worse mobility function and younger adults. Contrary to our hypothesis, the older group with better mobility function displayed a sustained increase in activation but the other groups did not, suggestive of neural compensation. Additional findings were that task-related increases in prefrontal cortical activation during walking were lateralized to the right hemisphere in older adults with better mobility function but were bilateral in older adults with worse mobility function and younger adults.

Discussion

These findings support that compared to walking on a flat surface, walking on uneven terrain surfaces increases demand on cognitive control resources as measured by prefrontal cortical activation.

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.

Patients with chronic ankle instability exhibit increased sensorimotor cortex activation and correlation with poorer lateral balance control ability during single-leg stance: a FNIRS study

Introduction

Chronic Ankle Instability (CAI) is a musculoskeletal condition that evolves from acute ankle sprains, and its underlying mechanisms have yet to reach a consensus. Mounting evidence suggests that neuroplastic changes in the brain following ankle injuries play a pivotal role in the development of CAI. Balance deficits are a significant risk factor associated with CAI, yet there is a scarcity of evidence regarding the sensorimotor cortical plasticity related to balance control in affected individuals. This study aims to evaluate the differences in cortical activity and balance abilities between patients with CAI and uninjured individuals during a single-leg stance, as well as the correlation between these factors, in order to elucidate the neurophysiological alterations in balance control among patients with CAI.

Methods

The study enrolled 24 patients with CAI and 24 uninjured participants. During single-leg stance, cortical activity was measured using a functional near-infrared spectroscopy (fNIRS) system, which included assessments of the pre-motor cortex (PMC), supplementary motor area (SMA), primary motor cortex (M1), and primary somatosensory cortex (S1). Concurrently, balance parameters were tested utilizing a three-dimensional force platform.

Results

Independent sample t-tests revealed that, compared with the uninjured individuals, the patients with CAI exhibited a significant increase in the changes of oxyhemoglobin concentration (ΔHbO) during single-leg stance within the left S1 at Channel 5 (t = 2.101, p = 0.041, Cohen's d = 0.607), left M1 at Channel 6 (t = 2.363, p = 0.022, Cohen's d = 0.682), right M1 at Channel 15 (t = 2.273, p = 0.029, Cohen's d = 0.656), and right PMC/SMA at Channel 11 (t = 2.467, p = 0.018, Cohen's d = 0.712). Additionally, the center of pressure root mean square (COP-RMS) in the mediolateral (ML) direction was significantly greater (t = 2.630, p = 0.012, Cohen's d = 0.759) in the patients with CAI. Furthermore, a moderate positive correlation was found between ML direction COP-RMS and ΔHbO2 in the M1 (r = 0.436; p = 0.033) and PMC/SMA (r = 0.488, p = 0.016), as well as between anteroposterior (AP) direction COP-RMS and ΔHbO in the M1 (r = 0.483, p = 0.017).

Conclusion

Patients with CAI demonstrate increased cortical activation in the bilateral M1, ipsilateral PMC/SMA, and contralateral S1. This suggests that patients with CAI may require additional brain resources to maintain balance during single-leg stance, representing a compensatory mechanism to uphold task performance amidst diminished lateral balance ability in the ankle joint.

Aerobic exercise on the treadmill combined with transcranial direct current stimulation on the gait of people with Parkinson's disease: A protocol for a randomized clinical trial

Gait impairments negatively affect the quality of life of people with Parkinson's disease (PwPD). Aerobic exercise (AE) is an alternative to alleviate these impairments and its combination with transcranial direct current stimulation (tDCS) has demonstrated synergistic effects. However, the effect of multitarget tDCS application (i.e., motor, and prefrontal cortices simultaneously) combined with physical exercise on gait impairments is still little known. Thus, the proposed randomized clinical trial will verify the acute effects of AE combined with tDCS applied on motor and prefrontal cortices separately and simultaneously on gait (spatial-temporal and cortical activity parameters) in PwPD. Twenty-four PwPD in Hoehn & Yahr stages I-III will be recruited for this crossover study. PwPD will practice AE on treadmill simultaneously with the application of anodal tDCS during four intervention sessions on different days (∼ one week of interval). Active tDCS will be applied to the primary motor cortex, prefrontal cortex, and both areas simultaneously (multitarget), with an intensity of 2 mA for 20 min. For sham, the stimulation will remain at 2 mA for 10 s. The AE will last a total of 30 min, consisting of warm-up, main part (20 min with application of tDCS), and recovery. Exercise intensity will be controlled by heart rate. Spatial-temporal and cortical activity parameters will be acquired before and after each session during overground walking, walking with obstacle avoidance, and walking with a cognitive dual task at self-preferred velocity. An accelerometer will be positioned on the fifth lumbar vertebra to obtain the spatial-temporal parameters (i.e., step length, duration, velocity, and swing phase duration). Prefrontal cortex activity will be recorded from a portable functional near-infrared spectroscopy system and oxygenated and deoxygenated hemoglobin concentrations will be analyzed. Two-way ANOVAs with repeated measures for stimulation and moment will be performed. The findings of the study may contribute to improving gait in PwPD. Trial registration: Brazilian Clinical Trials Registry (RBR-738zkp7).

Physical training improves inhibitory control in children aged 7-12 years: An fNIRS study

Physical exercise plays a crucial role in the development of cognition and brain functions in children. Inhibitory control is an advanced cognition that affects children's life and learning. In the current study, the relationship between physical training and inhibitory control was explored. In total, 80 children were randomly but equally assigned to the experimental and control groups. The experimental group underwent physical training (volleyball) for 60 min, thrice a week for 12 weeks. In contrast, the control group did not undergo any training and continued with their daily routines. The flanker task and functional near-infrared spectroscopy (fNIRS) were employed to investigate the effects of 12-week physical training on inhibitory control and changes in the oxy-Hb concentration in the prefrontal cortex (PFC) during the task. The behavioral results revealed that the experimental group performed better on the flanker task (e.g., shorter response time [F(1,74) = 18.420, p < 0.001, ηp2 = 0.199] and higher accuracy [F(1,74) = 15.00, p < 0.001, ηp2 = 0.169] than the control group. The oxy-Hb concentration in the right dorsolateral PFC (R-DLPFC) was higher and the activation level of this region was higher during the flanker task [F(1,74) = 6.216, p < 0.05, ηp2 = 0.077]. Moreover, the McNemar test revealed improved cognitive performance in response time or accuracy and R-DLPFC activation induced by physical exercise coincided significantly (χ2 = 5.49, p < 0.05; χ2 = 6.081, p < 0.05). These findings suggest that the R-DLPFC is likely the neural substrate for improved cognitive performance elicited by 12-week physical training.

Exercise promotes brain health: a systematic review of fNIRS studies

Exercise can induce brain plasticity. Functional near-infrared spectroscopy (fNIRS) is a functional neuroimaging technique that exploits cerebral hemodynamics and has been widely used in the field of sports psychology to reveal the neural mechanisms underlying the effects of exercise. However, most existing fNIRS studies are cross-sectional and do not include exercise interventions. In addition, attributed to differences in experimental designs, the causal relationship between exercise and brain functions remains elusive. Hence, this systematic review aimed to determine the effects of exercise interventions on alterations in brain functional activity in healthy individuals using fNIRS and to determine the applicability of fNIRS in the research design of the effects of various exercise interventions on brain function. Scopus, Web of Science, PubMed, CNKI, Wanfang, and Weipu databases were searched for studies published up to June 15, 2021. This study was performed in accordance with the PRISMA guidelines. Two investigators independently selected articles and extracted relevant information. Disagreements were resolved by discussion with another author. Quality was assessed using the Cochrane risk-of-bias method. Data were pooled using random-effects models. A total of 29 studies were included in the analysis. Our results indicated that exercise interventions alter oxygenated hemoglobin levels in the prefrontal cortex and motor cortex, which are associated with improvements in higher cognitive functions (e.g., inhibitory control and working memory). The frontal cortex and motor cortex may be key regions for exercise-induced promotion of brain health. Future research is warranted on fluctuations in cerebral blood flow during exercise to elucidate the neural mechanism underlying the effects of exercise. Moreover, given that fNIRS is insensitive to motion, this technique is ideally suited for research during exercise interventions. Important factors include the study design, fNIRS device parameters, and exercise protocol. The examination of cerebral blood flow during exercise intervention is a future research direction that has the potential to identify cortical hemodynamic changes and elucidate the relationship between exercise and cognition. Future studies can combine multiple study designs to measure blood flow prior to and after exercise and during exercise in a more in-depth and comprehensive manner.

Investigating cortical activity during cybersickness by fNIRS

This study investigated brain responses during cybersickness in healthy adults using functional near-infrared spectroscopy (fNIRS). Thirty participants wore a head-mounted display and observed a virtual roller coaster scene that induced cybersickness. Cortical activation during the virtual roller coaster task was measured using fNIRS. Cybersickness symptoms were evaluated using a Simulator Sickness Questionnaire (SSQ) administered after the virtual rollercoaster. Pearson correlations were performed for cybersickness symptoms and the beta coefficients of hemodynamic responses. The group analysis of oxyhemoglobin (HbO) and total hemoglobin (HbT) levels revealed deactivation in the bilateral angular gyrus during cybersickness. In the Pearson correlation analyses, the HbO and HbT beta coefficients in the bilateral angular gyrus had a significant positive correlation with the total SSQ and disorientation. These results indicated that the angular gyrus was associated with cybersickness. These findings suggest that the hemodynamic response in the angular gyrus could be a biomarker for evaluating cybersickness symptoms.

Parkinson's disease patients show delayed hemodynamic changes in primary motor cortex in fine motor tasks and decreased resting-state interhemispheric functional connectivity: a functional near-infrared spectroscopy study

Significance

People with Parkinson's disease (PD) experience changes in fine motor skills, which is viewed as one of the hallmark signs of this disease. Due to its non-invasive nature and portability, functional near-infrared spectroscopy (fNIRS) is a promising tool for assessing changes related to fine motor skills.

Aim

We aim to compare activation patterns in the primary motor cortex using fNIRS, comparing volunteers with PD and sex- and age-matched control participants during a fine motor task and walking. Moreover, inter and intrahemispheric functional connectivity (FC) was investigated during the resting state.

Approach

We used fNIRS to measure the hemodynamic changes in the primary motor cortex elicited by a finger-tapping task in 20 PD patients and 20 controls matched for age, sex, education, and body mass index. In addition, a two-minute walking task was carried out. Resting-state FC was also assessed.

Results

Patients with PD showed delayed hypoactivation in the motor cortex during the fine motor task with the dominant hand and delayed hyperactivation with the non-dominant hand. The findings also revealed significant correlations among various measures of hemodynamic activity in the motor cortex using fNIRS and different cognitive and clinical variables. There were no significant differences between patients with PD and controls during the walking task. However, there were significant differences in interhemispheric connectivity between PD patients and control participants, with a statistically significant decrease in PD patients compared with control participants.

Conclusions

Decreased interhemispheric FC and delayed activity in the primary motor cortex elicited by a fine motor task may one day serve as one of the many potential neuroimaging biomarkers for diagnosing PD.

Prefrontal cortex activation while walking did not change but gait speed improved after a randomized physical therapy intervention

BACKGROUND

Higher prefrontal cortex (PFC) activation while walking may indicate reduced gait automaticity.

AIM

We examine whether PFC activation during walking improves after training in older adults at risk for mobility disability.

METHODS

Forty-two adults aged ≥ 65 participated in a randomized clinical trial (NCT026637780) of a 12-week timing and coordination physical therapy intervention to improve walking (n = 20 intervention, n = 22 active control). PFC activation was measured by functional near-infrared spectroscopy (fNIRS) during four walking tasks over 15 m, each repeated 4 times: even surface walking, uneven surface walking, even dual-task, uneven dual-task; dual-task was reciting every other letter of the alphabet while walking. Gait speed and rate of correct letter generation were recorded. Linear mixed models tested between arm differences in change of fNIRS, gait speed, and letter generation from baseline to follow-up (12-week, 24-week, and 36-week).

RESULTS

Intervention arms were similar in mean age (74.3 vs. 77.0) and baseline gait speed (0.96 vs. 0.93 m/s). Of 24 comparisons of between arm differences in the fNIRS signals, only two were significant which were not supported by differences at other follow-up times or on other tasks. Gait speed, particularly during dual-task conditions, and correct letter generation did improve post-intervention but improvements did not differ by arm.

DISCUSSION AND CONCLUSIONS

After training, PFC activation during walking generally did not improve and did not differ by intervention arm. Improvements in gait speed without increased PFC activation may point toward more efficient neural control of walking.

Retrieval of chromophore concentration changes in a digital human head model using analytical mean partial pathlengths of photons

Significance

Continuous-wave functional near-infrared spectroscopy has proved to be a valuable tool for assessing hemodynamic activity in the human brain in a non-invasively and inexpensive way. However, most of the current processing/analysis methods assume the head is a homogeneous medium, and hence do not appropriately correct for the signal coming from the scalp. This effect can be reduced by considering light propagation in a layered model of the human head, being the Monte Carlo (MC) simulations the gold standard to this end. However, this implies large computation times and demanding hardware capabilities.

Aim

In this work, we study the feasibility of replacing the homogeneous model and the MC simulations by means of analytical multilayered models, combining in this way, the speed and simplicity of implementation of the former with the robustness and accuracy of the latter.

Approach

Oxy- and deoxyhemoglobin (HbO and HbR, respectively) concentration changes were proposed in two different layers of a magnetic resonance imaging (MRI)-based meshed model of the human head, and then these changes were retrieved by means of (i) a typical homogeneous reconstruction and (ii) a theoretical layered reconstruction.

Results

Results suggest that the use of analytical models of light propagation in layered models outperforms the results obtained using traditional homogeneous reconstruction algorithms, providing much more accurate results for both, the extra- and the cerebral tissues. We also compare the analytical layered reconstruction with MC-based reconstructions, achieving similar degrees of accuracy, especially in the gray matter layer, but much faster (between 4 and 5 orders of magnitude).

Conclusions

We have successfully developed, implemented, and validated a method for retrieving chromophore concentration changes in the human brain, combining the simplicity and speed of the traditional homogeneous reconstruction algorithms with robustness and accuracy much more similar to those provided by MC simulations.

Novel attentional gait index reveals a cognitive ability-related decline in gait automaticity during dual-task walking

Introduction

Gait automaticity refers to the ability to walk with minimal recruitment of attentional networks typically mediated through the prefrontal cortex (PFC). Reduced gait automaticity (i.e., greater use of attentional resources during walking) is common with aging, contributing to an increased risk of falls and reduced quality of life. A common assessment of gait automaticity involves examining PFC activation using near-infrared spectroscopy (fNIRS) during dual-task (DT) paradigms, such as walking while performing a cognitive task. However, neither PFC activity nor task performance in isolation measures automaticity accurately. For example, greater PFC activation could be interpreted as worse gait automaticity when accompanied by poorer DT performance, but when accompanied by better DT performance, it could be seen as successful compensation. Thus, there is a need to incorporate behavioral performance and PFC measurements for a more comprehensive evaluation of gait automaticity. To address this need, we propose a novel attentional gait index as an analytical approach that combines changes in PFC activity with changes in DT performance to quantify automaticity, where a reduction in automaticity will be reflected as an increased need for attentional gait control (i.e., larger index).

Methods

The index was validated in 173 participants (≥65 y/o) who completed DTs with two levels of difficulty while PFC activation was recorded with fNIRS. The two DTs consisted of reciting every other letter of the alphabet while walking over either an even or uneven surface.

Results

As DT difficulty increases, more participants showed the anticipated increase in the attentional control of gait (i.e., less automaticity) as measured by the novel index compared to PFC activation. Furthermore, when comparing across individuals, lower cognitive function was related to higher attentional gait index, but not PFC activation or DT performance.

Conclusion

The proposed index better quantified the differences in attentional control of gait between tasks and individuals by providing a unified measure that includes both brain activation and performance. This new approach opens exciting possibilities to assess participant-specific deficits and compare rehabilitation outcomes from gait automaticity interventions.

Cortical activity and spatiotemporal parameters during gait termination and walking: A preliminary study

Gait termination requires an interaction between the biomechanical and neuromuscular systems to arrest forward momentum. Currently, the biomechanical characteristics of gait termination have been demonstrated; however, the neural mechanism of gait termination remains unclear. This study aimed to investigate cortical activity during gait termination using functional near-infrared spectroscopy (fNIRS). Thirteen healthy younger adults (mean age:24.0 ± 1.7) participated in this study. All participants performed three experimental sessions: planned gait termination (PGT), unplanned gait termination (UGT), and walking. Each experimental session comprised a block paradigm design (three cycles; 20 s resting, 45 s task). Cortical activity in the dorsolateral prefrontal cortex (DLPFC), supplementary motor area (SMA), and primary motor cortex (M1) and spatiotemporal parameters were measured. We compared the cortical activities and spatiotemporal parameters among PGT, UGT, and walking sessions. In addition, we performed Pearson correlations between hemodynamic responses and spatiotemporal parameters. The PGT was activated in the right DLPFC, whereas the UGT and walking were activated in the left SMA (p < 0.05). Comparing cortical activation between sessions, both the PGT and UGT showed significantly higher activation in the right DLPFC than during walking (p < 0.05). There were no significant differences in cortical activity between PGT and UGT (p > 0.05). In addition, the gait termination time revealed moderate positive correlation with hemodynamic responses in the right DLPFC (p < 0.05). Our results indicate that the right DLPFC is associated with gait termination, regardless of gait termination type. Our findings provide the potential implication that the hemodynamic response in the right DLPFC would be a biomarker to evaluate the ability of gait termination.

Prefrontal cortex hemodynamic activity during a test of lower extremity functional muscle strength in children with cerebral palsy: A functional near-infrared spectroscopy study

Children with cerebral palsy (CP) exhibit impaired motor control and significant muscle weakness due to a brain lesion. However, studies that assess the relationship between brain activity and performance on dynamic functional muscle strength assessments in CP are needed. The aim of this study was to determine the effect of a progressive lateral step-up test on prefrontal cortex (PFC) hemodynamic activity in children with CP. Fourteen ambulatory children with spastic CP (Gross Motor Function Classification System level I; 5-11 y) and 14 age- and sex-matched typically developing control children completed a progressive lateral step-up test at incremental step heights (0, 10, 15 and 20 cm) using their non-dominant lower limb. Hemodynamic activity in the PFC was assessed using non-invasive, portable functional neuroimaging (functional near-infrared spectroscopy). Children with CP completed fewer repetitions at each step height and exhibited lower PFC hemodynamic activity across step heights compared to controls. Lower PFC activation in CP was maintained after statistically controlling for the number of repetitions completed at each step height. PFC hemodynamic activity was not associated with LSUT task performance in children with CP, but a positive relationship was observed in controls at the most challenging 20 cm step height. The results suggest there is an altered PFC recruitment pattern in children with CP during a highly dynamic test of functional strength. Further studies are needed to explore the mechanisms underlying the suppressed PFC activation observed in children with CP compared to typically developing children.

Quantification of dynamic cerebral autoregulation: welcome to the jungle!

PURPOSE

Patients with dysautonomia often experience symptoms such as dizziness, syncope, blurred vision and brain fog. Dynamic cerebral autoregulation, or the ability of the cerebrovasculature to react to transient changes in arterial blood pressure, could be associated with these symptoms.

METHODS

In this narrative review, we go beyond the classical view of cerebral autoregulation to discuss dynamic cerebral autoregulation, focusing on recent advances pitfalls and future directions.

RESULTS

Following some historical background, this narrative review provides a brief overview of the concept of cerebral autoregulation, with a focus on the quantification of dynamic cerebral autoregulation. We then discuss the main protocols and analytical approaches to assess dynamic cerebral autoregulation, including recent advances and important issues which need to be tackled.

CONCLUSION

The researcher or clinician new to this field needs an adequate comprehension of the toolbox they have to adequately assess, and interpret, the complex relationship between arterial blood pressure and cerebral blood flow in healthy individuals and clinical populations, including patients with autonomic disorders.

What happens in the prefrontal cortex? Cognitive processing of novel and familiar stimuli in soccer: An exploratory fNIRS study

The importance of both general and sport-specific perceptual-cognitive abilities in soccer players has been investigated in several studies. Although these perceptual-cognitive skills could contribute significantly to soccer players' expertise, the underlying cortical mechanisms have not been clarified yet. Examining activity changes in the prefrontal cortex under different cognitive demands may help to better understand the underlying mechanisms of sports expertise. The aim of this study was to analyse the prefrontal activity of soccer experts during general and sport-specific cognitive tasks. For this purpose, 39 semi-professional soccer players performed four perceptual-cognitive tests, two of which assessed general cognition, the other two assessed sport-specific cognition. Since soccer is a movement-intensive sport, two tests were performed in motion. While performing cognitive tests, prefrontal activity was recorded using functional near-infrared spectroscopy (fNIRS) (NIRSport, NIRx Medical Technologies, USA). Differences of prefrontal activity in general and sport-specific cognitive tasks were analysed using paired t-tests. The results showed significant increases in prefrontal activity during general cognitive tests (novel stimuli) compared to sport-specific tests (familiar stimuli). The comparatively lower prefrontal activity change during sport-specific cognition might be due to learned automatisms of experts in this field. These results seem in line with previous findings on novel and automated cognition, "repetition suppression theory" and "neural efficiency theory". Furthermore, the different cortical processes could be caused by altered prefrontal structures of experts and might represent a decisive factor for expertise in team sports. However, further research is needed to clarify the prefrontal involvement on expertise in general and sport-specific cognition.

Neural correlates of weight-shift training in older adults: a randomized controlled study

Mediolateral weight-shifting is an important aspect of postural control. As it is currently unknown whether a short training session of mediolateral weight-shifting in a virtual reality (VR) environment can improve weight-shifting, we investigated this question and also probed the impact of practice on brain activity. Forty healthy older adults were randomly allocated to a training (EXP, n = 20, age = 70.80 (65-77), 9 females) or a control group (CTR, n = 20, age = 71.65 (65-82), 10 females). The EXP performed a 25-min weight-shift training in a VR-game, whereas the CTR rested for the same period. Weight-shifting speed in both single- (ST) and dual-task (DT) conditions was determined before, directly after, and 24 h after intervention. Functional Near-Infrared Spectroscopy (fNIRS) assessed the oxygenated hemoglobin (HbO2) levels in five cortical regions of interest. Weight-shifting in both ST and DT conditions improved in EXP but not in CTR, and these gains were retained after 24 h. Effects transferred to wider limits of stability post-training in EXP versus CTR. HbO2 levels in the left supplementary motor area were significantly increased directly after training in EXP during ST (change < SEM), and in the left somatosensory cortex during DT (change > SEM). We interpret these changes in the motor coordination and sensorimotor integration areas of the cortex as possibly learning-related.

Effects of Training with a Powered Exoskeleton on Cortical Activity Modulation in Hemiparetic Chronic Stroke Patients: A Randomized Controlled Pilot Trial

OBJECTIVES

To investigate the effects of exoskeleton-assisted gait training in stroke patients.

DESIGN

Prospective randomized controlled trial.

SETTING

Rehabilitation department in a single tertiary hospital.

PARTICIPANTS

Thirty (N=30) chronic stroke patients with Functional Ambulatory Category scale (FAC) between 2 and 4.

INTERVENTION

Patients were randomly assigned to 1 of 2 groups: training with Healbot G, a wearable powered exoskeleton (Healbot G group; n=15), or treadmill training (control group; n=15). All participants received 30 minutes of training, 10 times per week, for 4 weeks.

OUTCOME MEASUREMENTS

The primary outcome was oxyhemoglobin level changes, representing cortical activity in both motor cortices using functional near-infrared spectroscopy. The secondary outcomes included FAC, Berg Balance Scale, Motricity Index for the lower extremities (MI-Lower), 10-meter walk test, and gait symmetry ratio (spatial step and temporal symmetry ratio).

RESULTS

Compared to the control group, during the entire training session, the pre-training and post-training mean cortical activity, and the amount of increment between pre- and post-training were significantly higher in the Healbot G group (∆mean ± SD; pre-training, 0.245±0.119, post-training, 0.697±0.429, between pre- and post-training, 0.471±0.401μmol, P<.001). There was no significant difference in cortical activity between affected- and unaffected hemispheres after Healbot G training. FAC (∆mean ± SD; 0.35 ± 0.50, P=.012), MI-Lower (∆mean ± SD; 7.01 ± 0.14, P=.001), and spatial step gait symmetry ratio (∆mean ± SD; -0.32 ± 0.25, P=.049) were improved significantly in the Healbot G group.

CONCLUSION

Exoskeleton-assisted gait training induces cortical modulation effect in both motor cortices, a balanced cortical activation pattern with improvements in spatial step symmetry ratio, walking ability, and voluntary strength.

[Motoric cognitive risk syndrome-Setting the course for dementia prevention?]

BACKGROUND

The predicted increase in adults with dementia will pose a major challenge for the German healthcare system. To mitigate this challenge, the early detection of adults with an increased risk of dementia is crucial. In this context, the concept of motoric cognitive risk (MCR) syndrome has been introduced into the English literature but is currently relatively unknown in German-speaking countries.

OBJECTIVE

What are the characteristics and diagnostic criteria of MCR? What is the impact of MCR on health-related parameters? What is the current state of evidence regarding the risk factors and prevention of the MCR?

MATERIAL AND METHODS

We reviewed the English language literature concerning MCR, the associated risk factors, and protective factors, similarities or differences with the concept of mild cognitive impairment (MCI), and its influence on the central nervous system.

RESULTS

The MCR syndrome is characterized by subjective cognitive impairment and a slower gait speed. Compared to healthy adults, adults with the MCR have a higher risk of dementia, falls, and mortality. Modifiable risk factors provide a starting point for specific multimodal lifestyle-related preventive interventions.

CONCLUSION

As MCR can be easily diagnosed in practical settings, it could become an important concept for the early detection of adults with an increased risk of dementia in German-speaking countries, although further research is necessary to empirically confirm this assumption.

Toward a Multi-Modal Brain-Body Assessment in Parkinson's Disease: A Systematic Review in fNIRS

Parkinson's disease (PD) causes impairments in cortical structures leading to motor and cognitive symptoms. While common disease management and treatment strategies mainly depend on the subjective assessment of clinical scales and patients' diaries, research in recent years has focused on advances in automatic and objective tools to help with diagnosing PD and determining its severity. Due to the link between brain structure deficits and physical symptoms in PD, objective brain activity and body motion assessment of patients have been studied in the literature. This study aimed to explore the relationship between brain activity and body motion measures of people with PD to look at the feasibility of diagnosis or assessment of PD using these measures. In this study, we summarised the findings of 24 selected papers from the complete literature review using the Scopus database. Selected studies used both brain activity recording using functional near-infrared spectroscopy (fNIRS) and motion assessment using sensors for people with PD in their experiments. Results include 1) the most common study protocol is a combination of single tasks. 2) Prefrontal cortex is mostly studied region of interest in the literature. 3) Oxygenated haemoglobin (HbO 2) concentration is the predominant metric utilised in fNIRS, compared to deoxygenated haemoglobin (HHb). 4) Motion assessment in people with PD is mostly done with inertial measurement units (IMUs) and electronic walkway. 5) The relationship between brain activity and body motion measures is an important factor that has been neglected in the literature.

Correlation Between Executive Function and Walk While Crossing Over an Obstacle Under Different Gait Phases

Background and Purpose

Dual walking task such as crossing over an obstacle may serve as an excellent tool for predicting early cognitive decline. Thus, this study aimed to investigate correlation between walking while crossing over an obstacle and executive functions under different gait phases to validate the use of walking with an obstacle for predicting early cognitive decline.

Methods

A cross-sectional study was conducted on 48 elderly individuals from 2 day-care centers and 3 welfare-centers in Seoul and Gyeonggi, Korea. Executive function tests (Trail Making Test, Stroop test) and dual walking tests (gait speed, cadence, stance time, gait cycle time) were performed and compared using partial correlation analysis.

Results

There were significant correlations between executive function and most of the gait variables (stance time, cadence, and gait cycle time) (p<0.05) when crossing over an obstacle while walking. Especially, stance time exhibited significant correlations with most executive functions (p<0.05).

Conclusions

When evaluating executive function during walking with an obstacle, post-obstacle-crossing phase and stance time need to be observed.

The different contributions of the eight prefrontal cortex subregions to reactive responses after unpredictable slip perturbations and vibrotactile cueing

Introduction

Recent advancements in functional near-infrared spectroscopy technology have offered a portable, wireless, wearable solution to measure the activity of the prefrontal cortex (PFC) in the human neuroscience field. This study is the first to validate the different contributions made by the PFC's eight subregions in healthy young adults to the reactive recovery responses following treadmill-induced unpredictable slip perturbations and vibrotactile cueing (i.e., precues).

Methods

Our fall-inducing technology platform equipped with a split-belt treadmill provided unpredictable slip perturbations to healthy young adults while walking at their self-selected walking speed. A portable, wireless, wearable, and multi-channel (48 channels) functional near-infrared spectroscopy system evaluated the activity of PFC's eight subregions [i.e., right and left dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), frontopolar prefrontal cortex (FPFC), and orbitofrontal cortex (OFC)] as quantified by oxyhemoglobin and deoxyhemoglobin concentrations. A motion capture system and two force plates beneath the split-belt treadmill were used to quantify participants' kinematic and kinetic behavior. All participants completed 6 trials: 2 consecutive trials without vibrotactile cueing and with a slip perturbation (control trials); 3 trials with vibrotactile cueing [2 trials with the slip perturbation (cueing trial) and 1 trial without the slip perturbation (catch trial)], and 1 trial without vibrotactile cueing and with a slip perturbation (post-control trial). The PFC subregions' activity and kinematic behavior were assessed during the three periods (i.e., standing, walking, and recovery periods).

Results

Compared to the walkers' standing and walking periods, recovery periods showed significantly higher and lower levels of oxyhemoglobin and deoxyhemoglobin concentrations, respectively, in the right and left DLPFC, VLPFC, and FPFC, regardless of the presence of vibrotactile cueing. However, there was no significant difference in the right and left OFC between the three periods. Kinematic analyses confirmed that vibrotactile cueing significantly improved reactive recovery responses without requiring more involvement by the PFC subregions, which suggests that the sum of attentional resources is similar in cued and non-cued motor responses.

Discussion

The results could inform the design of wearable technologies that alert their users to the risks of falling and assist with the development of new gait perturbation paradigms that prompt reactive responses.

Deep Learning Based Walking Tasks Classification in Older Adults Using fNIRS

Decline in gait features is common in older adults and an indicator of increased risk of disability, morbidity, and mortality. Under dual task walking (DTW) conditions, further degradation in the performance of both the gait and the secondary cognitive task were found in older adults which were significantly correlated to falls history. Cortical control of gait, specifically in the pre-frontal cortex (PFC) as measured by functional near infrared spectroscopy (fNIRS), during DTW in older adults has recently been studied. However, the automatic classification of differences in cognitive activations under single and dual task gait conditions has not been extensively studied yet. In this paper, by considering single task walking (STW) as a lower attentional walking state and DTW as a higher attentional walking state, we aimed to formulate this as an automatic detection of low and high attentional walking states and leverage deep learning methods to perform their classification. We conduct analysis on the data samples which reveals the characteristics on the difference between HbO2 and Hb values that are subsequently used as additional features. We perform feature engineering to formulate the fNIRS features as a 3-channel image and apply various image processing techniques for data augmentation to enhance the performance of deep learning models. Experimental results show that pre-trained deep learning models that are fine-tuned using the collected fNIRS dataset together with gender and cognitive status information can achieve around 81% classification accuracy which is about 10% higher than the traditional machine learning algorithms. We present additional sensitivity metrics such as confusion matrix, precision and F1 score, as well as accuracy on two-way classification between condition pairings. We further performed an extensive ablation study to evaluate factors such as the voxel locations, channels of input images, zero-paddings and pre-training of deep learning model on their contribution or impact to the classification task. Results showed that using pre-trained model, all the voxel locations, and HbO2 - Hb as the third channel of the input image can achieve the best classification accuracy.

Novel automaticity index reveals a cognitive ability-related decline in gait automaticity during dual-task walking

Gait automaticity refers to the ability to walk with minimal recruitment of attentional networks typically mediated through the prefrontal cortex (PFC). Reduced gait automaticity is common with aging, contributing to an increased risk of falls and reduced quality of life. A common assessment of gait automaticity involves examining PFC activation using near-infrared spectroscopy (fNIRS) during dual-task (DT) paradigms, such as walking while performing a cognitive task. However, neither PFC activity nor task performance in isolation measures automaticity accurately. For example, greater PFC activation could be interpreted as worse gait automaticity when accompanied by poorer DT performance, but when accompanied by better DT performance, it could be seen as successful compensation. Thus, there is a need to incorporate behavioral performance and PFC measurements for a more comprehensive evaluation of gait automaticity. To address this need, we propose a novel automaticity index as an analytical approach that combines changes in PFC activity with changes in DT performance to quantify gait automaticity. We validated the index in 173 participants (≥65 y/o) who completed DTs with two levels of difficulty while PFC activation was recorded with fNIRS. The two DTs consisted of reciting every other letter of the alphabet while walking over either an even or uneven surface. We found that as DT difficulty increases, more participants showed the anticipated decrease in automaticity as measured by the novel index compared to PFC activation. Furthermore, when comparing across individuals, lower cognitive function related to worse automaticity index, but not PFC activation or DT performance. In sum, the proposed index better quantified the differences in automaticity between tasks and individuals by providing a unified measure of gait automaticity that includes both brain activation and performance. This new approach opens exciting possibilities to assess participant-specific deficits and compare rehabilitation outcomes from gait automaticity interventions.

Transcranial direct current stimulation suggests not improving postural control during adapted tandem position in people with Parkinson's disease: A pilot study

BACKGROUND

Balance impairments in people with Parkinson's disease (PD) demonstrated mainly in challenging postural tasks, such as increased body oscillation may be attributed to the deficits in the brain structures functionality involved in postural control (e.g., motor cortex, midbrain, and brainstem). Although promising results, the effect of transcranial direct current stimulation (tDCS) on postural control in people with PD is unclear, especially in objective measures such as the center of pressure (CoP) parameters. Thus, we analyzed the effects of a single session of tDCS on the CoP parameters during the adapted tandem position in people with PD.

METHODS

Nineteen people with PD participated in this crossover, randomized, and double-blind study. Anodal tDCS was applied over the primary motor cortex in two conditions of stimulation (2 mA/active and sham) on two different days for 20 min immediately before the postural control evaluation. Participants remained standing in an adapted tandem position for the postural control assessment for 30 s (three trials). CoP parameters were acquired by a force plate.

RESULTS

No significant differences were demonstrated between stimulation conditions (p-value range = 0.15-0.89).

CONCLUSIONS

Our results suggested that a single session of tDCS with 2 mA does not improve the postural control of people with PD during adapted tandem.

Effect of automaticity induced by treadmill walking on prefrontal cortex activation and dual-task performance in older adults

As individuals age, they may experience a decline in gait automaticity, which requires increased attentional resources for the control of gait. This age-related decline in gait automaticity has been shown to contribute to higher prefrontal cortex (PFC) activation and lower dual-task performance during dual-task walking in older adults. This study is to investigate the effect of treadmill walking on PFC activation and dual-task performance in older adults. A total of 20 older adults (mean age, 64.35 ± 2.74 years) and 20 younger adults (mean age, 30.00 ± 3.15 years) performed single- and dual-task walking in overground and treadmill conditions. A wearable functional near-infrared spectroscopy and gait analyzer were used to analyze PFC activation and dual-task performance, respectively. To determine the dual-task (gait and cognitive) performance, the dual-task cost (DTC) was calculated using the following formula: (single-task - dual-task)/single-task × 100. In both groups, dual-task treadmill walking led to reduced PFC activation and reduced DTC compared to dual-task overground walking. Furthermore, despite a higher DTC in gait variability, correct response, total response, response index and a higher error score in older adults than in younger adults during overground walking, there was no difference in treadmill walking. The difference in PFC activation between single- and dual-tasks was also observed only in overground walking. Performing dual-task walking on a treadmill compared to overground walking results in different levels of dual-task performance and PFC activity. Specifically, older adults are able to maintain similar levels of dual-task performance as younger adults while walking on a treadmill, with reduced PFC activation due to the automaticity induced by the treadmill. Therefore, older adults who exhibit low dual-task performance during overground walking may be able to improve their performance while walking on a treadmill with fewer attentional resources.

Faster Walking Speeds Require Greater Activity from the Primary Motor Cortex in Older Adults Compared to Younger Adults

Gait speed declines with age and slower walking speeds are associated with poor health outcomes. Understanding why we do not walk faster as we age, despite being able to, has implications for rehabilitation. Changes in regional oxygenated haemoglobin (HbO2) across the frontal lobe were monitored using functional near infrared spectroscopy in 17 young and 18 older adults while they walked on a treadmill for 5 min, alternating between 30 s of walking at a preferred and fast (120% preferred) speed. Gait was quantified using a triaxial accelerometer (lower back). Differences between task (preferred/fast) and group (young/old) and associations between regional HbO2 and gait were evaluated. Paired tests indicated increased HbO2 in the supplementary motor area (right) and primary motor cortex (left and right) in older adults when walking fast (p < 0.006). HbO2 did not significantly change in the young when walking fast, despite both groups modulating gait. When evaluating the effect of age (linear mixed effects model), greater increases in HbO2 were observed for older adults when walking fast (prefrontal cortex, premotor cortex, supplementary motor area and primary motor cortex) compared to young adults. In older adults, increased step length and reduced step length variability were associated with larger increases in HbO2 across multiple regions when walking fast. Walking fast required increased activation of motor regions in older adults, which may serve as a therapeutic target for rehabilitation. Widespread increases in HbO2 across the frontal cortex highlight that walking fast represents a resource-intensive task as we age.

Cocoa flavanols protect cognitive function, cerebral oxygenation, and mental fatigue during severe hypoxia

We tested the hypothesis that ingestion of cocoa flavanols would improve cognition during acute hypoxia equivalent to 5,500 m altitude (partial pressure of end-tidal oxygen = 45 mmHg). Using placebo-controlled double-blind trials, 12 participants ingested 15 mg·kg-1 of cocoa flavanols 90 min before completing cognitive tasks during normoxia and either poikilocapnic or isocapnic hypoxia (partial pressure of end-tidal carbon dioxide uncontrolled or maintained at the baseline value, respectively). Cerebral oxygenation was measured using functional near-infrared spectroscopy. Overall cognition was impaired by poikilocapnic hypoxia (main effect of hypoxia, P = 0.008). Cocoa flavanols improved a measure of overall cognitive performance by 4% compared with placebo (effect of flavanols, P = 0.033) during hypoxia, indicating a change in performance from "low average" to "average." The hypoxia-induced decrease in cerebral oxygenation was two-fold greater with placebo than with cocoa flavanols (effect of flavanols, P = 0.005). Subjective fatigue was increased by 900% with placebo compared with flavanols during poikilocapnic hypoxia (effect of flavanols, P = 0.004). Overall cognition was impaired by isocapnic hypoxia (effect of hypoxia, P = 0.001) but was not improved by cocoa flavanols (mean improvement = 1%; effect of flavanols, P = 0.72). Reaction time was impaired by 8% with flavanols during normoxia and further impaired by 11% during isocapnic hypoxia (effect of flavanols, P = 0.01). Our findings are the first to show that flavanol-mediated improvements in cognition and mood during normoxia persist during severe oxygen deprivation, conferring a neuroprotective effect.NEW & NOTEWORTHY We show for the first time that cocoa flavanols exert a neuroprotective effect during severe hypoxia. Following acute cocoa flavanol ingestion, we observed improvements in cognition, cerebral oxygenation, and subjective fatigue during normoxia and severe poikilocapnic hypoxia. Cocoa flavanols did not improve cognition during severe isocapnic hypoxia, suggesting a possible interaction with carbon dioxide.

Deep learning-based framework for real-time upper limb motion intention classification using combined bio-signals

This research study proposes a unique framework that takes input from a surface electromyogram (sEMG) and functional near-infrared spectroscopy (fNIRS) bio-signals. These signals are trained using convolutional neural networks (CNN). The framework entails a real-time neuro-machine interface to decode the human intention of upper limb motions. The bio-signals from the two modalities are recorded for eight movements simultaneously for prosthetic arm functions focusing on trans-humeral amputees. The fNIRS signals are acquired from the human motor cortex, while sEMG is recorded from the human bicep muscles. The selected classification and command generation features are the peak, minimum, and mean ΔHbO and ΔHbR values within a 2-s moving window. In the case of sEMG, wavelength, peak, and mean were extracted with a 150-ms moving window. It was found that this scheme generates eight motions with an enhanced average accuracy of 94.5%. The obtained results validate the adopted research methodology and potential for future real-time neural-machine interfaces to control prosthetic arms.

Change in activity patterns in the prefrontal cortex in different phases during the dual-task walking in older adults

BACKGROUND

Studies using functional near-infrared spectroscopy (fNIRS) have shown that dual-task walking leads to greater prefrontal cortex (PFC) activation compared to the single-task walking task. However, evidence on age-related changes in PFC activity patterns is inconsistent. Therefore, this study aimed to explore the changes in the activation patterns of PFC subregions in different activation phases (early and late phases) during both single-task and dual-task walking in both older and younger adults.

METHODS

Overall, 20 older and 15 younger adults performed a walking task with and without a cognitive task. The activity of the PFC subregions in different phases (early and late phases) and task performance (gait and cognitive task) were evaluated using fNIRS and a gait analyzer.

RESULTS

The gait (slower speed and lower cadence) and cognitive performance (lower total response, correct response and accuracy rate, and higher error rate) of older adults was poorer during the dual task than that of younger adults. Right dorsolateral PFC activity in the early period in older adults was higher than that in younger adults, which declined precipitously during the late period. Conversely, the activity level of the right orbitofrontal cortex in the dual-task for older adults was lower than for younger adults.

CONCLUSIONS

These altered PFC subregion-specific activation patterns in older adults would indicate a decline in dual-task performance with aging.

Facilitating or disturbing? An investigation about the effects of auditory frequencies on prefrontal cortex activation and postural sway

Auditory stimulation activates brain areas associated with higher cognitive processes, like the prefrontal cortex (PFC), and plays a role in postural control regulation. However, the effects of specific frequency stimuli on upright posture maintenance and PFC activation patterns remain unknown. Therefore, the study aims at filling this gap. Twenty healthy adults performed static double- and single-leg stance tasks of 60s each under four auditory conditions: 500, 1000, 1500, and 2000 Hz, binaurally delivered through headphones, and in quiet condition. Functional near-infrared spectroscopy was used to measure PFC activation through changes in oxygenated hemoglobin concentration, while an inertial sensor (sealed at the L5 vertebra level) quantified postural sway parameters. Perceived discomfort and pleasantness were rated through a 0-100 visual analogue scale (VAS). Results showed that in both motor tasks, different PFC activation patterns were displayed at the different auditory frequencies and the postural performance worsened with auditory stimuli, compared to quiet conditions. VAS results showed that higher frequencies were considered more discomfortable than lower ones. Present data prove that specific sound frequencies play a significant role in cognitive resources recruitment and in the regulation of postural control. Furthermore, it supports the importance of exploring the relationship among tones, cortical activity, and posture, also considering possible applications with neurological populations and people with hearing dysfunctions.

A pilot study to explore the effect of udenafil on cerebral hemodynamics in older adults

OBJECTIVE

Phosphodiesterase-5 inhibitors (PDE5Is) enhance vasodilation. We investigated the effects of PDE5I on cerebral hemodynamics during cognitive tasks using functional near-infrared spectroscopy (fNIRS).

METHODS

This study used a crossover design. Twelve cognitively healthy men participants (mean age, 59 ± 3 years; range, 55-65 years) were recruited and randomly assigned to the experimental or control arm, then the experimental and control arm were exchanged after 1 week. Udenafil 100 mg was administered to participants in the experimental arm once daily for 3 days. We measured the fNIRS signal during the resting state and four cognitive tasks three times for each participant: at baseline, in the experimental arm, and in the control arm.

RESULTS

Behavioral data did not show a significant difference between the experimental and control arms. The fNIRS signal showed significant decreases in the experimental arm compared to the control arm during several cognitive tests: verbal fluency test (left dorsolateral prefrontal cortex, T = -3.02, p = 0.014; left frontopolar cortex, T = -4.37, p = 0.002; right dorsolateral prefrontal cortex, T = -2.59, p = 0.027), Korean-color word Stroop test (left orbitofrontal cortex, T = -3.61, p = 0.009), and social event memory test (left dorsolateral prefrontal cortex, T = -2.35, p = 0.043; left frontopolar cortex, T = -3.35, p = 0.01).

INTERPRETATION

Our results showed a paradoxical effect of udenafil on cerebral hemodynamics in older adults. This contradicts our hypothesis, but it suggests that fNIRS is sensitive to changes in cerebral hemodynamics in response to PDE5Is.

Associations between gait performance and pain intensity, psychosocial factors, executive functions as well as prefrontal cortex activity in chronic low back pain patients: A cross-sectional fNIRS study

Introduction

Activities of daily living, such as walking, are impaired in chronic low back pain (CLBP) patients compared to healthy individuals. Thereby, pain intensity, psychosocial factors, cognitive functioning and prefrontal cortex (PFC) activity during walking might be related to gait performance during single and dual task walking (STW, DTW). However, to the best of our knowledge, these associations have not yet been explored in a large sample of CLBP patients.

Method

Gait kinematics (inertial measurement units) and PFC activity (functional near-infrared spectroscopy) during STW and DTW were measured in 108 CLBP patients (79 females, 29 males). Additionally, pain intensity, kinesiophobia, pain coping strategies, depression and executive functioning were quantified and correlation coefficients were calculated to determine the associations between parameters.

Results

The gait parameters showed small correlations with acute pain intensity, pain coping strategies and depression. Stride length and velocity during STW and DTW were (slightly to moderately) positively correlated with executive function test performance. Specific small to moderate correlations were found between the gait parameters and dorsolateral PFC activity during STW and DTW.

Conclusion

Patients with higher acute pain intensity and better coping skills demonstrated slower and less variable gait, which might reflect a pain minimization strategy. Psychosocial factors seem to play no or only a minor role, while good executive functions might be a prerequisite for a better gait performance in CLBP patients. The specific associations between gait parameters and PFC activity during walking indicate that the availability and utilization of brain resources are crucial for a good gait performance.

Between-sessions test-retest reliability of prefrontal cortical activity during usual walking in patients with Parkinson's Disease: A fNIRS study

BACKGROUND

Examining between-sessions test-retest reliability of functional near-infrared spectroscopy (fNIRS) data is crucial to better interpret rehabilitation-related changes in the hemodynamic response.

RESEARCH QUESTION

This study investigated test-retest reliability of prefrontal activity during usual walking in 14 patients with Parkinson's Disease with a fixed retest intervals of five weeks.

METHODS

Fourteen patients performed usual walking in two sessions (T0 and T1). Relative changes in cortical activity (oxy and deoxyhemoglobin: ∆HbO₂ and ∆HbR, respectively) in the dorsolateral prefrontal cortex (DLPFC) using fNIRS system and gait performance were measured. Test-retest reliability of mean ∆HbO₂ for the total DLPFC and for each hemisphere were measured using paired t-test, intraclass correlation coefficient (ICC), and Bland-Altman plots with 95% agreement. Pearson correlations between cortical activity and gait performance were also performed.

RESULTS

Moderate reliability was found for ∆HbO₂ in the total DLPFC (mean difference of ∆HbO₂ between T1 and T0 = -0.005 µmol, p = 0.93; ICC average = 0.72). However, test-retest reliability of ∆HbO₂ was poorer when considering each hemisphere.

SIGNIFICANCE

Findings suggest that fNIRS may be used as a reliable tool for rehabilitation studies in patients with PD. Test-retest reliability of fNIRS data between 2 sessions during walking tasks should be interpreted respectively of gait performance.

Increased Cortical Activity in Novices Compared to Experts During Table Tennis: A Whole-Brain fNIRS Study Using Threshold-Free Cluster Enhancement Analysis

There is a growing interest to understand the neural underpinnings of high-level sports performance including expertise-related differences in sport-specific skills. Here, we aimed to investigate whether expertise level and task complexity modulate the cortical hemodynamics of table tennis players. 35 right-handed table tennis players (17 experts/18 novices) were recruited and performed two table tennis strokes (forehand and backhand) and a randomized combination of them. Cortical hemodynamics, as a proxy for cortical activity, were recorded using functional near-infrared spectroscopy, and the behavioral performance (i.e., target accuracy) was assessed via video recordings. Expertise- and task-related differences in cortical hemodynamics were analyzed using nonparametric threshold-free cluster enhancement. In all conditions, table tennis experts showed a higher target accuracy than novices. Furthermore, we observed expertise-related differences in widespread clusters compromising brain areas being associated with sensorimotor and multisensory integration. Novices exhibited, in general, higher activation in those areas as compared to experts. We also identified task-related differences in cortical activity including frontal, sensorimotor, and multisensory brain areas. The present findings provide empirical support for the neural efficiency hypothesis since table tennis experts as compared to novices utilized a lower amount of cortical resources to achieve superior behavioral performance. Furthermore, our findings suggest that the task complexity of different table tennis strokes is mirrored in distinct cortical activation patterns. Whether the latter findings can be useful to monitor or tailor sport-specific training interventions necessitates further investigations.

Left and Right Cortical Activity Arising from Preferred Walking Speed in Older Adults

Cortical activity and walking speed are known to decline with age and can lead to an increased risk of falls in the elderly. Despite age being a known contributor to this decline, individuals age at different rates. This study aimed to analyse left and right cortical activity changes in elderly adults regarding their walking speed. Cortical activation and gait data were obtained from 50 healthy older individuals. Participants were then grouped into a cluster based on their preferred walking speed (slow or fast). Analyses on the differences of cortical activation and gait parameters between groups were carried out. Within-subject analyses on left and right-hemispheric activation were also performed. Results showed that individuals with a slower preferred walking speed required a higher increase in cortical activity. Individuals in the fast cluster presented greater changes in cortical activation in the right hemisphere. This work demonstrates that categorizing older adults by age is not necessarily the most relevant method, and that cortical activity can be a good indicator of performance with respect to walking speed (linked to fall risk and frailty in the elderly). Future work may wish to explore how physical activity training influences cortical activation over time in the elderly.

fNIRS is sensitive to leg activity in the primary motor cortex after systemic artifact correction

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<0.001) and significant HbO increases of moderate effect size in the medial M1 channels during foot tapping (Cohen's d = 0.8, p<0.05). The cortical activity differences between automatic and non-automatic tasks were not significantly different. Importantly, leg movements produced large systemic fluctuations, which were adequately removed by the use of all available short channels.

DISCUSSION

Our results indicate that fNIRS is sensitive to leg activity in M1, though the sensitivity is lower than for finger activity and requires rigorous correction for systemic fluctuations. We furthermore highlight that systemic artifacts may result in an unreliable GLM analysis when short channels show signals that are similar to the expected hemodynamic responses.

Reconstruction of light absorption changes in the human head using analytically computed photon partial pathlengths in layered media

Functional near infrared spectroscopy has been used in recent decades to sense and quantify changes in hemoglobin concentrations in the human brain. This noninvasive technique can deliver useful information concerning brain cortex activation associated with different motor/cognitive tasks or external stimuli. This is usually accomplished by considering the human head as a homogeneous medium; however, this approach does not explicitly take into account the detailed layered structure of the head, and thus, extracerebral signals can mask those arising at the cortex level. This work improves this situation by considering layered models of the human head during reconstruction of the absorption changes in layered media. To this end, analytically calculated mean partial pathlengths of photons are used, which guarantees fast and simple implementation in real-time applications. Results obtained from synthetic data generated by Monte Carlo simulations in two- and four-layered turbid media suggest that a layered description of the human head greatly outperforms typical homogeneous reconstructions, with errors, in the first case, bounded up to ∼20% maximum, while in the second case, the error is usually larger than 75%. Experimental measurements on dynamic phantoms support this conclusion.

Muscular and Prefrontal Cortex Activity during Dual-Task Performing in Young Adults

Postural control depends on attentional resources besides automatic processes. The dual-task paradigm is a possible approach to analyzing the interference and performance between motor and/or cognitive tasks. Various studies showed that, when individuals simultaneously perform two tasks, the postural stability can decline during a dual-task compared with a single-task due to the attentional resources required performing the tasks. However, little is known about the cortical and muscular activity pattern during dual-task performance. Therefore, this study aims to analyze the muscular and prefrontal activity under dual-task performance in healthy young adults. Thirty-four healthy young adults (mean age ± SD = 22.74 ± 3.74 years) were recruited to perform a postural task (standing posture) and a dual-task (maintaining standing posture while performing a cognitive task). Lower-limb muscle activity was bilaterally collected from five muscles using surface electromyography (sEMG), and the co-contraction index (CCI) was also calculated for selected muscle pairings. The oxy- and deoxyhemoglobin concentrations (prefrontal cortex activity) were recorded using functional near-infrared spectroscopy (fNIRS). Data were compared between single- and dual-task performance. Prefrontal activity increased (p < 0.05), and muscle activity decreased in most analyzed muscles (p < 0.05), from the single-task to cognitive dual-task performing. The co-contraction index patterns changed from single- to dual-task conditions in most selected muscle pairs (p < 0.05). We conclude that the cognitive task negatively interfered with motor performance once the muscle activity decreased and the prefrontal cortex activity increased under a dual-task, suggesting that young adults prioritized cognitive task performance, and they allocated more attentional resources to the cognitive task over the motor performance. Understanding the neuromotor changes can help adopt a better clinical practice to prevent injuries. However, future studies are recommended to assess and monitor muscular and cortical activity during the dual-task performance to provide additional information about the cortical and muscular activity patterns in postural control while performing a dual-task.

Relationship between motor performance and cortical activity of older neurological disorder patients with dyskinesia using fNIRS: A systematic review

Background: Neurological disorders with dyskinesia would seriously affect older people’s daily activities, which is not only associated with the degeneration or injury of the musculoskeletal or the nervous system but also associated with complex linkage between them. This study aims to review the relationship between motor performance and cortical activity of typical older neurological disorder patients with dyskinesia during walking and balance tasks.

Methods: Scopus, PubMed, and Web of Science databases were searched. Articles that described gait or balance performance and cortical activity of older Parkinson’s disease (PD), multiple sclerosis, and stroke patients using functional near-infrared spectroscopy were screened by the reviewers. A total of 23 full-text articles were included for review, following an initial yield of 377 studies.

Results: Participants were mostly PD patients, the prefrontal cortex was the favorite region of interest, and walking was the most popular test motor task, interventional studies were four. Seven studies used statistical methods to interpret the relationship between motor performance and cortical activation. The motor performance and cortical activation were simultaneously affected under difficult walking and balance task conditions. The concurrent changes of motor performance and cortical activation in reviewed studies contained the same direction change and different direction change.

Conclusion: Most of the reviewed studies reported poor motor performance and increased cortical activation of PD, stroke and multiple sclerosis older patients. The external motor performance such as step speed were analyzed only. The design and results were not comprehensive and profound. More than 5 weeks walking training or physiotherapy can contribute to motor function promotion as well as cortices activation of PD and stroke patients. Thus, further study is needed for more statistical analysis on the relationship between motor performance and activation of the motor-related cortex. More different type and program sports training intervention studies are needed to perform.

Carbon dioxide protects simulated driving performance during severe hypoxia

PURPOSE

We sought to determine the effect of acute severe hypoxia, with and without concurrent manipulation of carbon dioxide (CO₂), on complex real-world psychomotor task performance.

METHODS

Twenty-one participants completed a 10-min simulated driving task while breathing room air (normoxia) or hypoxic air (P_ETO₂ = 45 mmHg) under poikilocapnic, isocapnic, and hypercapnic conditions (P_ETCO₂ = not manipulated, clamped at baseline, and clamped at baseline + 10 mmHg, respectively). Driving performance was assessed using a fixed-base motor vehicle simulator. Oxygenation in the frontal cortex was measured using functional near-infrared spectroscopy.

RESULTS

Speed limit exceedances were greater during the poikilocapnic than normoxic, hypercapnic, and isocapnic conditions (mean exceedances: 8, 4, 5, and 7, respectively; all p ≤ 0.05 vs poikilocapnic hypoxia). Vehicle speed was greater in the poikilocapnic than normoxic and hypercapnic conditions (mean difference: 0.35 km h^-1 and 0.67 km h^-1, respectively). All hypoxic conditions similarly decreased cerebral oxyhaemoglobin and increased deoxyhaemoglobin, compared to normoxic baseline, while total hemoglobin remained unchanged.

CONCLUSIONS

These findings demonstrate that supplemental CO₂ can confer a neuroprotective effect by offsetting impairments in complex psychomotor task performance evoked by severe poikilocapnic hypoxia; however, differences in performance are unlikely to be linked to measurable differences in cerebral oxygenation.

Inefficient frontal and parietal brain activation during dual-task walking in a virtual environment in older adults

Walking while performing an additional cognitive task (dual-task walking; DT walking) is a common yet highly demanding behavior in daily life. Previous neuroimaging studies have shown that performance declines from single- (ST) to DT conditions are accompanied by increased prefrontal cortex (PFC) activity. This increment is particularly pronounced in older adults and has been explained either by compensation, dedifferentiation, or ineffective task processing in fronto-parietal circuits. However, there is only limited evidence for the hypothesized fronto-parietal activity changes measured under real life conditions such as walking. In this study, we therefore assessed brain activity in PFC and parietal lobe (PL), to investigate whether higher PFC activation during DT walking in older adults is related to compensation, dedifferentiation, or neural inefficiency. Fifty-six healthy older adults (69.11 ± 4.19 years, 30 female) completed three tasks (treadmill walking at 1 m/s, Stroop task, Serial 3's task) under ST and DT conditions (Walking + Stroop, Walking + Serial 3's), and a baseline Standing task. Behavioral outcomes were step time variability (Walking), Balance Integration Score BIS (Stroop), and number of correct calculations S3_corr (Serial 3's). Brain activity was measured using functional near-infrared spectroscopy (fNIRS) over ventrolateral and dorsolateral PFC (vlPFC, dlPFC) and inferior and superior PL (iPL, sPL). Neurophysiological outcome measures were oxygenated (HbO₂) and deoxygenated hemoglobin (HbR). Linear mixed models with follow-up estimated marginal means contrasts were applied to investigate region-specific upregulations of brain activation from ST to DT conditions. Furthermore, the relationships of DT-specific activations across all brain regions was analyzed as well as the relationship between changes in brain activation and changes in behavioral performance from ST to DT. Data indicated the expected upregulation from ST to DT and that DT-related upregulation was more pronounced in PFC (particularly in vlPFC) than in PL regions. Activation increases from ST to DT were positively correlated between all brain regions, and higher brain activation changes predicted higher declines in behavioral performance from ST to DT. Results were largely consistent for both DTs (Stroop and Serial 3's). These findings more likely suggest neural inefficiency and dedifferentiation in PFC and PL rather than fronto-parietal compensation during DT walking in older adults. Findings have implications for interpreting and promoting efficacy of long-term interventions to improve DT walking in older persons.

Greater prefrontal activation during sitting toe tapping predicts severer freezing of gait in Parkinson's disease: an fNIRS study

OBJECTIVE

Previous studies have revealed that, compared with Parkinson's disease (PD) patients without freezing of gait (FoG), the ones with FoG showed greater prefrontal activation while doing lower-limb movements involving standing, walking and turning, which require both locomotor and balance control. However, the relation between FoG and pure locomotor control as well as its underlying mechanism remain unclear.

METHODS

A total of 56 PD subjects were recruited and allocated to PD-FoG and PD-noFoG subgroups, and 34 age-matched heathy adults were included as heathy control (HC). Functional near-infrared spectroscopy was used to measure their prefrontal activation in a sitting lower-limb movement task, wherein subjects were asked to sit and tap their right toes as big and as fast as possible.

RESULTS

Result of one-way ANOVA (Group: PD-FoG vs. PD-noFoG vs. HC) revealed greater activation in the right prefrontal cortex in the PD-FoG group than in the other 2 groups. Linear mixed-effects model showed consistent result. Furthermore, the right prefrontal activation positively correlated with the severity of FoG symptoms in PD-FoG patients.

CONCLUSION

These findings suggested that PD patients with FoG require additional cognitive resources to compensate their damaged automaticity in locomotor control, which is more pronounced in severe FoG patients than milder ones.

Changes in cortical activation during upright stance in individuals with chronic low back pain: An fNIRS study

Introduction

Postural control deficits are a potential cause of persistent and recurrent pain in patients with chronic low back pain (CLBP). Although some studies have confirmed that the dorsolateral prefrontal cortex (DLPFC) contributes to pain regulation in CLBP, its role in the postural control of patients with CLBP remains unclear. Therefore, this study aimed to investigate the DLPFC activation of patients with CLBP and healthy controls under different upright stance task conditions.

Methods

Twenty patients with CLBP (26.50 ± 2.48 years) and 20 healthy controls (25.75 ± 3.57 years) performed upright stance tasks under three conditions: Task-1 was static balance with eyes open; Task-2 was static balance with eyes closed; Task-3 involved dynamic balance on an unstable surface with eyes open. A wireless functional near-infrared spectroscopy (fNIRS) system measured cortical activity, including the bilateral DLPFC, pre-motor cortex (PMC) and supplementary motor area (SMA), the primary motor cortex (M1), the primary somatosensory cortex (S1), and a force platform measured balance parameters during upright stance.

Results

The two-way repeated measures ANOVA results showed significant interaction in bilateral PMC/SMA activation. Moreover, patients with CLBP had significantly increased right DLPFC activation and higher sway 32 area and velocity than healthy controls during upright stance.

Discussion

Our results imply that PMC/SMA and DLPFC maintain standing balance. The patients with CLBP have higher cortical activity and upright stance control deficits, which may indicate that the patients with CLBP have low neural efficiency and need more motor resources to maintain balance.