Increased prefrontal cortical activation during challenging walking conditions in persons with lower limb amputation - an fNIRS observational study

Hybrid Functional Near-Infrared Spectroscopy System and Electromyography for Prosthetic Knee Control

The increasing number of individuals with limb loss worldwide highlights the need for advancements in prosthetic knee technology. To improve control and quality of life, integrating brain-computer communication with motor imagery offers a promising solution. This study introduces a hybrid system that combines electromyography (EMG) and functional near-infrared spectroscopy (fNIRS) to address these limitations and enhance the control of knee movements for individuals with above-knee amputations. The study involved an experiment with nine healthy male participants, consisting of two sessions: real execution and imagined execution using motor imagery. The OpenBCI Cyton board collected EMG signals corresponding to the desired movements, while fNIRS monitored brain activity in the prefrontal and motor cortices. The analysis of the simultaneous measurement of the muscular and hemodynamic responses demonstrated that combining these data sources significantly improved the classification accuracy compared to using each dataset alone. The results showed that integrating both the EMG and fNIRS data consistently achieved a higher classification accuracy. More specifically, the Support Vector Machine performed the best during the motor imagery tasks, with an average accuracy of 49.61%, while the Linear Discriminant Analysis excelled in the real execution tasks, achieving an average accuracy of 89.67%. This research validates the feasibility of using a hybrid approach with EMG and fNIRS to enable prosthetic knee control through motor imagery, representing a significant advancement potential in prosthetic technology.

Perceptions of prosthetic attention among lower limb prosthesis users: a focus group study

PURPOSE

Use of a lower limb prosthesis generally requires increased cognitive effort to compensate for missing motor and sensory inputs. This study sought to examine how lower limb prosthesis users perceive paying attention to their prosthesis(es) in daily life.

MATERIALS AND METHODS

Focus groups with lower limb prosthesis users were conducted virtually using semi-structured questions. Verbatim transcripts were excerpted, coded, and reconciled. Inductive thematic analysis was undertaken to identify experiences shared by participants.

RESULTS

Five themes emerged from five focus groups conducted with thirty individuals: Paying attention to my prosthesis is just what I have to do; I pay attention to how my prosthetic socket fits and feels every day; I pay attention because I don't want to fall; I pay attention because I have to learn to do things in a new way; and If I can trust that my prosthesis will do what I want, I can pay less attention to it.

CONCLUSIONS

Prosthetic attention, including both background and foreground attention, is a shared experience among lower limb prosthesis users. The amount and frequency of prosthetic attention fluctuates throughout the day and changes over time. Measuring attention could inform the evaluation and prescription of technology intended to reduce cognitive effort.

Recent progress on smart lower prosthetic limbs: a comprehensive review on using EEG and fNIRS devices in rehabilitation

The global rise in lower limb amputation cases necessitates advancements in prosthetic limb technology to enhance the quality of life for affected patients. This review paper explores recent advancements in the integration of EEG and fNIRS modalities for smart lower prosthetic limbs for rehabilitation applications. The paper synthesizes current research progress, focusing on the synergy between brain-computer interfaces and neuroimaging technologies to enhance the functionality and user experience of lower limb prosthetics. The review discusses the potential of EEG and fNIRS in decoding neural signals, enabling more intuitive and responsive control of prosthetic devices. Additionally, the paper highlights the challenges, innovations, and prospects associated with the incorporation of these neurotechnologies in the field of rehabilitation. The insights provided in this review contribute to a deeper understanding of the evolving landscape of smart lower prosthetic limbs and pave the way for more effective and user-friendly solutions in the realm of neurorehabilitation.

Energy expenditure during typical household and community activities of daily living in persons with lower limb amputation: A pilot study

INTRODUCTION

Knowledge about the energy expenditure of typical activities of daily living (ADL) in persons with lower limb amputation (LLA) is lacking. This study investigated the following: (1) oxygen consumption per unit distance (V̇O 2 ; mL·kg -1 ·min -1 ), (2) proportion utilization of peak oxygen consumption (%V̇O 2 peak), (3) oxygen cost (energy cost; mL·kg -1 ·m -1 ), and (4) perceived exertion (rating of perceived exertion) of ADL in persons with LLA and able-bodied controls.

METHODS

Participants (21 with LLA/12 controls) performed 2 household ADL experiments: in-house walking and vacuuming and 3 community ADL experiments: marked shopping, fast walking, and stair negotiation. V̇O 2 peak was assessed with arm crank ergometry, and ambulatory activity was monitored for 7 days with a StepWatch.

RESULTS

Participants with LLA performed in-house walking, marked shopping, vacuuming, and stair negotiation at a similar V̇O 2 as controls, while their self-selected walking speed (WS) was significantly lower. Participants with LLA had significantly higher %V̇O 2 peak than controls during in-house walking and reported a significantly higher rating of perceived exertion for vacuuming and marked shopping. The highest possible WS of participants with LLA during fast walking was significantly lower than that of controls, but V̇O 2 was also significantly lower, indicating a limited capacity to walk at higher WS. Participants with LLA had a significantly lower daily step count, significantly lower-proportion high-intensity ambulation, but significantly higher-proportion low-intensity ambulation than controls, indicating that persons with LLA also walked at lower WS in daily life.

CONCLUSIONS

The results indicate that persons with LLA have increased physical and perceived effort during performance of ADL compared with persons without amputation, which has consequences for community participation, and hence independence and quality of life.

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.

Primary Motor Area Activity in Phantom Limb Imagery of Traumatic Unilateral Lower Limb Amputees With Phantom Limb Pain

Introduction

Estimates of the worldwide increase in amputees raises the awareness to solve long-standing problems. Understanding the functional brain modifications after a lower limb amputation (LLA) is one of the first steps towards proposing new rehabilitation approaches. Functional modifications in the central nervous system due the amputation could be involved in prosthesis use failures and Phantom Limb Pain (PLP), increasing costs and overwhelming the health services.

Objective

This study analyses orphan primary motor area (M1-Orphan) hemodynamic and metabolic behaviour, which previously controlled the limb that was amputated, in comparison with the M1-Preserved, responsible for the intact limb (IL) during phantom limb imagery moving during Mirror Therapy (MT), compared to Isolated Intact Limb Movement Task (I-ILMT).

Methodology

A case-control study with unilateral traumatic LLA with moderate PLP who measured [oxy-Hb] and [deoxy-Hb] in the M1 area by Functional Near InfraredSpectroscopy (fNIRS) during the real (I-ILMT) and MT task.

Results

Sixty-five patients, with 67.69% of men, young (40.32 ± 12.91), 65.63% amputated due motorcycle accidents, 4.71 ± 7.38 years ago, predominantly above the knee (57.14%). The M1 activation in the orphan cortex did not differ from the activation in the intact cortex during MT (P > .05).

Conclusion

The perception of the Phantom limb moving or intact limb moving is metabolically equivalent in M1, even in the absence of a limb. In other words, the amputation does not alter the brain metabolism in control of phantom movement.

The effect of dual-task testing on the balance and gait of people with lower limb amputations: A systematic review

OBJECTIVE

To systematically review the literature on the effect of dual-task testing on the balance and gait of people with lower limb amputations (PLLA).

LITERATURE SURVEY

Databases MEDLINE, EMBASE, CINAHL, PsycINFO, Web of Science, and Scopus were searched in duplicate (inception to December 1, 2020).

METHODOLOGY

Inclusion criteria: participants were adults with transtibial, knee-disarticulation, transfemoral, or bilateral lower limb amputations; balance or gait was paired with a secondary task; and studies were peer-reviewed and published in English. Two authors independently reviewed articles and consensus was required. A standardized data extraction sheet was used to gather study relevant information in duplicate. Methodological quality of reporting was examined using the Downs and Black Scale. A meta-analysis was unable to be performed owing to substantial participant and protocol heterogeneity among the studies included.

SYNTHESIS

Of 3950 articles screened, 22 met inclusion criteria. Four assessed dual-task balance and 18 dual-task gait. During single-task standing, PLLA demonstrated higher sway distance and sway velocity than controls (CN); however, a greater dual-task effect was observed only for sway velocity. Gait pace, rhythm, variability, asymmetry, and postural control were observed to be worse in PLLA relative to CN during single-task. Dual-task gait testing resulted in a disproportionally reduced pace and rhythm and increased asymmetry in PLLA compared to CN.

CONCLUSIONS

People with lower limb amputations have impaired balance and gait, which is affected by dual-task to a greater degree compared to healthy adults. An examination of how PLLA-specific factors such as level of amputation, reason for amputation, and experience with a prosthesis affect dual-task performance has not yet been thoroughly explored. Future research should continue to characterize the cognitive-mobility link to better understand the challenges associated with the use of a prosthesis.

An Overview on Cognitive Function Enhancement through Physical Exercises

This review is extensively focused on the enhancement of cognitive functions while performing physical exercises categorized into cardiovascular exercises, resistance training, martial arts, racquet sports, dancing and mind-body exercises. Imaging modalities, viz. functional magnetic resonance imaging (fMRI), functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG), have been included in this review. This review indicates that differences are present in cognitive functioning while changing the type of physical activity performed. This study concludes that employing fNIRS helps overcome certain limitations of fMRI. Further, the effects of physical activity on a diverse variety of the population, from active children to the old people, are discussed.

Modifications in Prefrontal Cortex Oxygenation in Linear and Curvilinear Dual Task Walking: A Combined fNIRS and IMUs Study

Increased oxygenated hemoglobin concentration of the prefrontal cortex (PFC) has been observed during linear walking, particularly when there is a high attention demand on the task, like in dual-task (DT) paradigms. Despite the knowledge that cognitive and motor demands depend on the complexity of the motor task, most studies have only focused on usual walking, while little is known for more challenging tasks, such as curved paths. To explore the relationship between cortical activation and gait biomechanics, 20 healthy young adults were asked to perform linear and curvilinear walking trajectories in single-task and DT conditions. PFC activation was assessed using functional near-infrared spectroscopy, while gait quality with four inertial measurement units. The Figure-of-8-Walk-Test was adopted as the curvilinear trajectory, with the "Serial 7s" test as concurrent cognitive task. Results show that walking along curvilinear trajectories in DT led to increased PFC activation and decreased motor performance. Under DT walking, the neural correlates of executive function and gait control tend to be modified in response to the cognitive resources imposed by the motor task. Being more representative of real-life situations, this approach to curved walking has the potential to reveal crucial information and to improve people' s balance, safety, and life's quality.