We tested the feasibility for amputees to control artificial limbs using non-invasive electroencephalography (EEG). Thirteen participants engaged in attempts of isometric ankle plantar-flexions using their phantom or intact limb at slow or ballistic speeds. EEG data were analyzed for movement-related cortical potentials (MRCPs), the slow negative potentials related to the planning and execution of movements. We focused on temporal profiles and single-trial classification at electrode location Cz where MRCPs are most prominent. Distinctly different MRCP morphologies were observed for both movement speeds and phantom versus intact limbs. Crucially, time since amputation correlated significantly with classification errors for distinguishing tasks performed with the intact limb from those of the phantom limb (R = 0.36, p =0.004) and movement speed during trials of only the phantom limb (R = -0.33, p = 0.01). Here we show the persistent capacity of amputees to plan and attempt to execute limb motions at varying speeds using their phantom limb. This has implications for understanding neural adaptations over extended post-amputation periods and for the practical implementation of the MRCP in the design of brain-computer interfaces to control prosthetic devices using single-electrode EEG recordings.

Electrode arrays along peripheral nerves can record sensory, motor and autonomic signals propagating in afferent and efferent direction at different conduction velocities. To extract this temporal information in a delay-and-sum approach, velocity-selective recording (VSR) utilizes summation to amplify time-aligned action potentials and average out noise. This improved contrast subsequently improves the automated detection and classification of action potentials - an essential prerequisite to interface with the peripheral nervous system. In this study, we replaced the summation with multiplication and investigated resulting signal changes. We focused on two derived methods: Lock-IN-Dispersion-Analysis (LINDA) multiplies all recorded signals; Delay-Combinatory-Multiply-And-Sum (DCMAS) multiplies all combinations of an adjustable number of signals and sums the products. Processing simulated neural array recordings, we compared the effects of LINDA and DCMAS on contrast-to-noise ratio (CNR), signal-to-noise-and distortion ratio (SINAD) and AP detectability after thresholding. Compared to VSR, both methods increased CNR, SINAD, and AP detectability but also introduced noise intermodulation distortion which limited SINAD gains. Additionally, LINDA formed a logical AND-gate between signals, suppressing interfering signal peaks. Overall, by increasing CNR, signal multiplication may improve decoding of array recordings, despite increased signal distortion. It may thereby advance neural interfaces for fundamental research, diagnostics or applications in bioelectronic medicine and neuroprostheses.

Patients with a lower limb amputation suffer from an impaired balance control and thereby are at a higher risk to fall. To cope with this deficit, they adapt their neuromuscular system by modifying biomechanical and neuromuscular structures. In this study, we investigated changes in corticomuscular coherence between the motor cortex and muscles of the trunk and the intact lower leg. We recorded electroencephalogram (EEG) and electromyogram (EMG) data from 10 unilateral transfemoral amputees and 10 age-matched able-bodied controls during quiet upright stance with eyes open, eyes closed and during dual tasking. To analyse afferent and efferent corticomuscular coherence, directional wavelet coherence between EEG and EMG signals was computed. The corticomuscular coherence analysis showed significant differences between amputees and controls in the afferent and efferent direction and across visual conditions, suggesting differences in the processing of sensory feedback. A power spectral density analysis of the motor cortex contralateral to the amputated leg of amputees showed increased power, as well as a pronounced decrease in alpha frequencies indicating an increased cognitive load. This exploratory study stimulates further hypotheses on how coordination of brain and muscle activity is modulated after a lower limb amputation.

Sensory feedback arising from muscles in the lower limb make an important contribution to the activation of muscles on the opposite side. To date little is known about this interlimb communication for muscles of the upper leg. Here we quantify interlimb reflexes of the quadriceps muscles elicited by femoral nerve stimulation. The reflex response of 10 able-bodied participants was analyzed at eight stimulation intensities (0.7x motor threshold (MT) - 100 % maximal M-wave (M-max)), during standing and sitting. EMG signals of the contralateral vastus lateralis (cVL), rectus femoris (cRF), biceps femoris (cBF) and soleus (cSOL) muscle were analyzed. Significant inhibitory long-latency responses were observed at stimulation intensities higher than 0.7xMT, for the cVL and cRF. Onset latencies ranged from 67 ± 12 ms - 70 ± 13 ms during standing and from 61 ± 14 ms - 67 ± 15 ms during sitting. The strongest depression (- 32,39 % compared to baseline EMG activity) was observed for the cRF during standing at 50 % M-max. The cBF showed excitatory long-latency responses during standing (strongest at 100 % M-max with + 52.36 %) and inhibitory once during sitting, as well as small excitatory short-latency responses during standing. The cSOL showed inhibitory long-latency responses (- 18.15 % at 25 % M-max) during standing. In conclusion, the results show that femoral nerve stimulation elicits consistent contralateral reflex responses in the quadriceps muscles. The occurrence at all intensities suggests that group Ia, Ib and II afferents are involved in the pathways.

Para cross-country (XC) skiing has become a prominent sport since its debut at the Örnsköldsvik Winter Olympic Games in 1976. Nevertheless, the lack of studies focusing on standing para XC skiing highlights the need to provide a comprehensive description of this sport, investigating how different prosthetic devices may influence the athletic outcome. In this exploratory case study, the biomechanics of an elite standing para-athlete, with a right-sided transfemoral amputation, was investigated. Tests were performed during diagonal XC skiing on a treadmill, at different speeds and inclinations. Specifically, two different prosthetic feet were compared: the athlete used an Ottobock Genium X3 prosthetic knee with either the Ottobock Taleo or the Ottobock Evanto prosthetic foot. Inertial Measurement Units (IMUs) were employed to estimate joint angles and detect pole hits and lifts. Additionally, data were collected using embedded sensors in the knee prosthesis. Diagonal stride spatiotemporal parameters were further calculated. Results revealed that the Evanto foot significantly increased swing phase duration and hip range of motion, while generating higher knee torque, ankle torque, and axial loading compared to the Taleo foot. This research represents the first application of the employed testing methodology to para standing XC skiing, and it therefore provides a framework for future studies on this discipline.

Engineers, neuroscientists, neurosurgeons, orthopedists and physiotherapists strive to develop and optimize bidirectional neural interfaces for patients wearing artificial limbs. Despite substantial progress made in the last decades, the sensory feedback delivered to patients remains only near-natural and difficult to convey. We believe that incorporating knowledge on neural control of movement may facilitate the design of novel bionic limbs. Identifying neuromuscular adaptations after limb amputation and characterizing their motor control response toward a bionic limb may be of great benefit. Here we review and comment on the opportunity to integrate these important aspects to minimize uncertainties while developing the next generation of bionic limbs.

Goal: Transcutaneous coupling scheme for wireless powering and signal in active implants are known for more than a decade. This study aimed to investigate the in vivo behavior of this approach to drive multiple channels of an implanted peripheral nerve interfaces. Methods: The stimulation signals were transmitted through the skin over two contacts to an intracorporeal counterpart which was connected to a cuff electrode with two channels. EMG after stimulation was measured to establish recruitment curves. Results: Limitations of transcutaneous coupling were found in the feasible complexity of the system. High electrical crosstalk in a multi-channel system reduces this approach to low channel applications, such as pain treatment. No significant influence of the pulse width or extracorporeal stimulation amplitude on the electrical crosstalk was observed. Conclusions: The study's findings provide insight into the behavior of the transcutaneous coupling scheme in vivo and highlight the limitations and areas of application. Our results indicate that transcutaneous coupling schemes are a promising alternative approach for wireless powering of implants, as it does not require complex implanted electronics, expensive sophisticated electronics, and hermetic enclosures. Physical constraints, however, limit the use in highly selective nerve stimulation scenarios

BACKGROUND:Patients with spinal cord injury (SCI) or with severe brain stroke suffer from life-lasting functional and sensory impairments. Other traumatic injuries such as limb loss after an accident or disease also affect motor function and sensory feedback and impair quality of life in those individuals. Invasive and non-invasive functional electrical stimulation (FES) is a well-established method to partially restore function and sensory feedback of paralyzed and phantom limbs. It is also a supporting technology for the rehabilitation of the neuromuscular system and for complementing assistive devices. METHODS:This work reviews the current state-of-the-art of FES as a technology for restoring function and supporting rehabilitation therapy and assistive devices. RESULTS:Electrodes, electrical stimulation, use of brain signals for rehabilitation and control, and sensory feedback are covered as parts of the whole. A perspective is given on how clinical and research protocols developed for patients with SCI and brain injuries can be translated to the treatment of patients with an amputation and vice versa. We further elaborate on how motor learning strategies with quantitative electrophysiological and kinematic measurements may help caregivers in the rehabilitation process. Insights from practitioners (collected during a workshop of the IFESS 2025) have been integrated to summarize common needs, open questions, and challenges. CONCLUSIONS:The information from the literature and from practitioners was integrated to propose the next steps towards establishing common guidelines and measures of FES in clinical practice towards evidence-driven treatment and objective assessments.

Purpose Many individuals with a lower limb amputation experience problems with the fitting of the socket of their prosthesis, leading to dissatisfaction or device rejection. Osseointegration (OI)- the implantation of a shaft directly interfacing with the remaining bone- is an alternative for these patients. In this observational study, we investigated how bone anchoring influences neuromuscular parameters during balance control in a patient with a unilateral transfemoral amputation.Material and methods Center of pressure (CoP) and electromyography (EMG) signals from muscles controlling the hip and the ankle of the intact leg were recorded during quiet standing six months before and one and a half years after this patient underwent an OI surgery. Results were compared to a control group of nine able-bodied individuals.Results Muscle co-activation and EMG intensity decreased after bone anchoring, approaching the levels of able-bodied individuals. Muscle co-activation controlling the ankle decreased in the high-frequency range, and the EMG intensity spectrum decreased in the lower-frequency range for all muscles when vision was allowed. With eyes closed, the ankle extensor muscle showed an increased EMG intensity in the high-frequency range post-surgery. CoP length increased in the mediolateral direction of the amputated leg.Conclusions These findings point to shifts in the patient's neuromuscular profile towards the one of able-bodied individuals.

BACKGROUND/OBJECTIVE:Plant-based diets reduce the risk of cardiovascular disease but also increase the risk of certain micronutrient deficiencies, particularly, of vitamin B12 (B12). The extent to which the unsupervised use of oral nutrient supplements is sufficient to prevent these deficiencies is not well established. We analyzed nutrient intake, laboratory biomarkers, supplementation behavior, and B12 status adequacy amongst young, healthy, physically active omnivores, lacto-ovo-vegetarians and vegans from Germany. METHODS:We recruited 115 participants (n = 40 omnivores; n = 37 lacto-ovo-vegetarians, and n = 38 vegans) with comparable age, sex, marital status, physical activity and educational levels through online advertisements and local newspapers in Freiburg, Germany. RESULTS:Energy intake and macronutrient distribution were comparable across diets. Major differences included intake of fiber, cholesterol, and several vitamins. Vegans had the lowest intake of B12 from foods (0.43 (0.58) µg/d), compared to omnivores (2.14 (2.29) µg/d) and lacto-ovo-vegetarians (0.98 (1.34) µg/day). Multivariate analysis of 36 blood biomarkers revealed that three major classes of biomarkers contributed the most to the clustering of individuals by dietary group, namely, biomarkers of B12 status (B12, holoTC, Hcy), iron (iron, ferritin, transferrin) and lipid metabolism (vitamin A, HDL, LDL, total cholesterol, TAG). This suggests that nutrients that modify the metabolic pathways represented by these biomarkers have the most penetrating effect on health status across diets. Analysis of B12 status (including 4cB12) revealed adequacy in omnivores and vegans, and a poorer B12 status amongst lacto-ovo-vegetarians. Fewer lacto-ovo-vegetarians used B12 supplements compared to vegans (51% versus 90%). CONCLUSIONS:Even amongst homogeneously healthy Germans, each diet manifested with measurable differences in dietary intakes and biomarkers of health. Plant-based diets, in particular the vegan diet, exhibited the most favorable patterns of lipid metabolism and glycemic control, but the lowest food intake of B12. Supplementation of healthy vegans with B12 (median 250 µg B12/day, over 2 years) secured an adequate B12 status that was comparable to that of healthy omnivores.Clinical Trial Registry: German Clinical Trial register number: DRKS00027425.

Precise control of bionic limbs relies on robust decoding of motor commands from nerves or muscles signals and sensory feedback from artificial limbs to the nervous system by interfacing the afferent nerve pathways. Implantable devices for bidirectional communication with bionic limbs have been developed in parallel with research on physiological alterations caused by an amputation. In this perspective article, we question whether increasing our effort on bridging these technologies with a deeper understanding of amputation pathophysiology and human motor control may help to overcome pressing stalls in the next generation of bionic limbs.

Objective. Somatosensory perception is disrupted in patients with a lower limb amputation. This increases the difficulty to maintain balance and leads to the development of neuromuscular adjustments. We investigated how these adjustments are reflected in the co-activation of lower body muscles and are modulated by visual feedback. Approach. We measured electromyography (EMG) signals of muscles from the trunk (erector spinae and obliquus external), and the lower intact/dominant leg (tibialis anterior and medial gastrocnemius) in 11 unilateral transfemoral amputees and 11 age-matched able-bodied controls during 30 s of upright standing with and without visual feedback. Muscle synergies involved in balance control were investigated using wavelet coherence analysis. We focused on seven frequencies grouped in three frequency bands, a low-frequency band (7.56 and 19.86 Hz) representing more sub-cortical and spinal inputs to the muscles, a mid-frequency band (38.26 and 62.63 Hz) representing more cortical inputs, and a high-frequency band (92.90, 129 and 170.90 Hz) associated with synchronizing motor unit action potentials. Further, the dynamics of changes in intermuscular coupling over time were quantified using the Entropic Half-Life. Main results. Amputees exhibited lower coherency values when vision was removed at 7.56 Hz for the muscle pair of the lower leg. At this frequency, the coherency values of the amputee group also differed from controls for the eyes closed condition. Controls and amputees exhibited opposite coherent behaviors with visual feedback at 7.56 Hz. For the eyes open condition at 129 Hz, the coherency values of amputees and controls differed for the muscle pair of the trunk, and at 170.90 Hz for the muscle pair of the lower leg. Amputees exhibited different dynamics of muscle co-activation at the low frequency band when vision was available. Significance. Altogether, these findings point to the development of neuromuscular adaptations reflected in the strength and dynamics of muscular co-activation.

1 Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany, 2 KITE Research Institute, University Health Network, Toronto, ON, Canada, 3 Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada, Machine Learning and Data Analytics Lab, Department of Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, 5 Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany, 6 BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany

Patients with a lower limb amputation rely more on visual feedback to maintain balance than able-bodied individuals. Altering this sensory modality in amputees thus results in a disrupted postural control. However, little is known about how lower limb amputees cope with augmented visual information during balance tasks. In this study, we investigated how unilateral transfemoral amputees incorporate visual feedback of their center of pressure (CoP) position during quiet standing. Ten transfemoral amputees and ten age-matched able-bodied participants were provided with real-time visual feedback of the position of their CoP while standing on a pressure platform. Their task was to keep their CoP within a small circle in the center of a computer screen placed at eye level, which could be achieved by minimizing their postural sway. The visual feedback was then delayed by 250 and 500 ms and was combined with a two- and five-fold amplification of the CoP displacements. Trials with eyes open without augmented visual feedback as well as with eyes closed were further performed. The overall performance was measured by computing the sway area. We further quantified the dynamics of the CoP adjustments using the entropic half-life (EnHL) to study possible physiological mechanisms behind postural control. Amputees showed an increased sway area compared to the control group. The EnHL values of the amputated leg were significantly higher than those of the intact leg and the dominant and non-dominant leg of controls. This indicates lower dynamics in the CoP adjustments of the amputated leg, which was compensated by increasing the dynamics of the CoP adjustments of the intact leg. Receiving real-time visual feedback of the CoP position did not significantly reduce the sway area neither in amputees nor in controls when comparing with the eyes open condition without visual feedback of the CoP position. Further, with increasing delay and amplification, both groups were able to compensate for small visual perturbations, yet their dynamics were significantly lower when additional information was not received in a physiologically relevant time frame. These findings may be used for future design of neurorehabilitation programs to restore sensory feedback in lower limb amputees.

Objective. Report simple reference structure fabrication and validate the precise localization of subdural micro- and standard electrodes in magnetic resonance imaging (MRI) in phantom experiments. Approach. Electrode contacts with diameters of 0.3 mm and 4 mm are localized in 1.5 T MRI using reference structures made of silicone and iron oxide nanoparticle doping. The precision of the localization procedure was assessed for several standard MRI sequences and implant orientations in phantom experiments and compared to common clinical localization procedures. Main results. A localization precision of 0.41 ± 0.20 mm could be achieved for both electrode diameters compared to 1.46 ± 0.69 mm that was achieved for 4 mm standard electrode contacts localized using a common clinical standard method. The new reference structures are intrinsically bio-compatible, and they can be detected with currently available feature detection software so that a clinical implementation of this technology should be feasible. Significance. Neuropathologies are increasingly diagnosed and treated with subdural electrodes, where the exact localization of the electrode contacts with respect to the patient’s cortical anatomy is a prerequisite for the procedure. Post-implantation electrode localization using MRI may be advantageous compared to the common alternative of CT-MRI image co-registration, as it avoids systematic localization errors associated with the co-registration itself, as well as brain shift and implant movement. Additionally, MRI provides superior soft tissue contrast for the identification of brain lesions without exposing the patient to ionizing radiation. Recent studies show that smaller electrodes and high-density electrode grids are ideal for clinical and research purposes, but the localization of these devices in MRI has not been demonstrated.

Objective: Chronic neural implants require energy and signal supply. The objective of this work was to evaluate a multichannel transcutaneous coupling approach in an ex vivo split-concept study, which minimizes the invasiveness of such an implant by externalizing the processing electronics. Methods: Herein, the experimental work focused on the transcutaneous energy and signal transmission. The performance was discussed with widely evaluated concepts of neural interfaces in the literature. Results: The performance of the transcutaneous coupling approach increased with higher channel count and higher electrode pitches. Electrical crosstalk among channels was present, but acceptable for the stimulation of peripheral nerves. Conclusions: Transcutaneous coupling with extracorporeal transmitting arrays and subcutaneous counterparts provide a promising alternative to the inductive concept particularly when a fully integration of the system in a prosthetic shaft is intended. The relocation of the electronics can potentially prevent pressure sores, improve accessibility for maintenance and increase lifetime of the implant.

The dynamics of the adjustment of center of pressure (CoP) has been utilized to understand motor control in human pathologies characterized by impairments in postural balance. The control mechanisms that maintain balance can be investigated via the analysis of muscle recruitment using electromyography (EMG) signals. In this work, we combined these two techniques to investigate balance control during upright standing in transfemoral unilateral amputees wearing a prosthesis. The dynamics of the CoP adjustments and EMG-EMG coherence between four muscles of the trunk and lower limb of 5 unilateral transfemoral amputees and 5 age-matched able-bodied participants were quantified during 30 s of quiet standing using the entropic half-life (EnHL) method. Two visual conditions, eyes open and eyes closed, were tested. Overall, the group of amputees presented lower EnHL values (higher dynamics) in their CoP adjustments than controls, especially in their intact limb. The EnHL values of the EMG-EMG coherence time series in the amputee group were lower than the control group for almost all muscle pairs under both visual conditions. Different correlations between the EnHL values of the CoP data and the EMG-EMG coherence data were observed in the amputee and control groups. These preliminary results suggest the onset of distinct neuromuscular adaptations following a unilateral amputation.Clinical Relevance - Understanding neuromuscular adaptation mechanisms after an amputation may serve to design better rehabilitation treatments and novel prosthetic devices with sensory feedback.

Abstract Background Following an amputation, the human postural control system develops neuromuscular adaptations to regain an effective postural control. We investigated the compensatory mechanisms behind these adaptations and how sensorimotor integration is affected after a lower-limb transfemoral amputation. Methods Center of pressure (CoP) data of 12 unilateral transfemoral amputees and 12 age-matched able-bodied subjects were recorded during quiet standing with eyes open (EO) and closed (EC). CoP adjustments under each leg were recorded to study their contribution to posture control. The spatial structure of the CoP displacements was characterized by measuring the mean distance, the mean velocity of the CoP adjustments, and the sway area. The Entropic Half-Life (EnHL) quantifies the temporal structure of the CoP adjustments and was used to infer disrupted sensory feedback loops in amputees. We expanded the analysis with measures of weight-bearing imbalance and asymmetry, and with two standardized balance assessments, the Berg Balance Scale (BBS) and Timed Up-and-Go (TUG). Results There was no difference in the EnHL values of amputees and controls when combining the contributions of both limbs (p = 0.754). However, amputees presented significant differences between the EnHL values of the intact and prosthetic limb (p < 0.001). Suppressing vision reduced the EnHL values of the intact (p = 0.001) and both legs (p = 0.028), but not in controls. Vision feedback in amputees also had a significant effect (increase) on the mean CoP distance (p < 0.001), CoP velocity (p < 0.001) and sway area (p = 0.007). Amputees presented an asymmetrical stance. The EnHL values of the intact limb in amputees were positively correlated to the BBS scores (EO: ρ = 0.43, EC: ρ = 0.44) and negatively correlated to the TUG times (EO: ρ = − 0.59, EC: ρ = − 0.69). Conclusion These results suggest that besides the asymmetry in load distribution, there exist neuromuscular adaptations after an amputation, possibly related to the loss of sensory feedback and an altered sensorimotor integration. The EnHL values suggest that the somatosensory system predominates in the control of the intact leg. Further, suppressing the visual system caused instability in amputees, but had a minimal impact on the CoP dynamics of controls. These findings points toward the importance of providing somatosensory feedback in lower-limb prosthesis to reestablish a normal postural control. Trial registration DRKS00015254, registered on September 20th, 2018.

[1][2]Department of Electronics and Telecommunication ------------------------------------------------------------------------***------------------------------------------------------------------------Abstract Gait monitoring using IOT is an important medical diagnostic process for stroke patient. We will design and implement an IOT system with Wi-Fi communication model and smart phone to discreetly monitor insole pressure of the patient’s motion. this system is helpful for fall detection, the best way to reduce number of falls and to predict and prevent them from happening in first place.in this system an Internet based body sensors are used which is a wireless portable network used for gait detection and prevention of fall in stroke patient.