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Journal articleSturma A, Hruby LA, Boesendorfer A, et al., 2021,
Therapy Interventions for Upper Limb Amputees Undergoing Selective Nerve Transfers
, Jove-Journal of Visualized Experiments, ISSN: 1940-087XTargeted Muscle Reinnervation (TMR) improves the biological control interface for myoelectric prostheses after above-elbow amputation. Selective activation of muscle units is made possible by surgically re-routing nerves, yielding a high number of independent myoelectric control signals. However, this intervention requires careful patient selection and specific rehabilitation therapy. Here a rehabilitation protocol is presented for high-level upper limb amputees undergoing TMR, based on an expert Delphi study. Interventions before surgery include detailed patient assessment and general measures for pain control, muscle endurance and strength, balance, and range of motion of the remaining joints. After surgery, additional therapeutic interventions focus on edema control and scar treatment and the selective activation of cortical areas responsible for upper limb control. Following successful reinnervation of target muscles, surface electromyographic (sEMG) biofeedback is used to train the activation of the novel muscular units. Later on, a table-top prosthesis may provide the first experience of prosthetic control. After fitting the actual prosthesis, training includes repetitive drills without objects, object manipulation, and finally, activities of daily living. Ultimately, regular patient appointments and functional assessments allow tracking prosthetic function and enabling early interventions if malfunctioning.
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Journal articleMartinez-Valdes E, Negro F, Arvanitidis M, et al., 2021,
Pain-induced changes in motor unit discharge depend on recruitment threshold and contraction speed.
, J Appl Physiol (1985), Vol: 131, Pages: 1260-1271At high forces, the discharge rates of lower- and higher-threshold motor units (MU) are influenced in a different way by muscle pain. These differential effects may be particularly important for performing contractions at different speeds since the proportion of lower- and higher-threshold MUs recruited varies with contraction velocity. We investigated whether MU discharge and recruitment strategies are differentially affected by pain depending on their recruitment threshold (RT), across a range of contraction speeds. Participants performed ankle dorsiflexion sinusoidal-isometric contractions at two frequencies (0.25 and 1 Hz) and two modulation amplitudes [5% and 10% of the maximum voluntary contraction (MVC)] with a mean target torque of 20%MVC. High-density surface electromyography recordings from the tibialis anterior muscle were decomposed and the same MUs were tracked across painful (hypertonic saline injection) and nonpainful conditions. Torque variability, mean discharge rate (MDR), DR variability (DRvar), RT, and the delay between the cumulative spike train and the resultant torque output (neuromechanical delay, NMD) were assessed. The average RT was greater at faster contraction velocities (P = 0.01) but was not affected by pain. At the fastest contraction speed, torque variability and DRvar were reduced (P < 0.05) and MDR was maintained. Conversely, MDR decreased and DRvar and NMD increased significantly during pain at slow contraction speeds (P < 0.05). These results show that reductions in contraction amplitude and increased recruitment of higher-threshold MUs at fast contraction speeds appear to compensate for the inhibitory effect of nociceptive inputs on lower-threshold MUs, allowing the exertion of fast submaximal contractions during pain.NEW & NOTEWORTHY Pain induces changes in motor performance, motor unit recruitment, and rate coding behavior that varies across different contraction speeds. Here we show that that pain reduces motor unit
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Journal articleLuft M, Klepetko J, Muceli S, et al., 2021,
Proof of concept for multiple nerve transfers to a single target muscle
, eLife, Vol: 10, Pages: 1-16, ISSN: 2050-084XSurgical nerve transfers are used to efficiently treat peripheral nerve injuries, neuromas,phantom limb pain, or improve bionic prosthetic control. Commonly, one donor nerve is transferredto one target muscle. However, the transfer of multiple nerves onto a single target muscle mayincrease the number of muscle signals for myoelectric prosthetic control and facilitate the treatmentof multiple neuromas. Currently, no experimental models are available. This study describes anovel experimental model to investigate the neurophysiological effects of peripheral double nervetransfers to a common target muscle. In 62 male Sprague-Dawleyrats, the ulnar nerve of the antebrachiumalone (n=30) or together with the anterior interosseus nerve (n=32) was transferred to reinnervatethe long head of the biceps brachii. Before neurotization, the motor branch to the biceps’long head was transected at the motor entry point. Twelve weeks after surgery, muscle responseto neurotomy, behavioral testing, retrograde labeling, and structural analyses were performed toassess reinnervation. These analyses indicated that all nerves successfully reinnervated the targetmuscle. No aberrant reinnervation was observed by the originally innervating nerve. Our observationssuggest a minimal burden for the animal with no signs of functional deficit in daily activities orauto-mutilationin both procedures. Furthermore, standard neurophysiological analyses for nerveand muscle regeneration were applicable. This newly developed nerve transfer model allows for thereliable and standardized investigation of neural and functional changes following the transfer ofmultiple donor nerves to one target muscle.
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Journal articleAliakbaryhosseinabadi S, Dosen S, Savic AM, et al., 2021,
Participant-specific classifier tuning increases the performance of hand movement detection from EEG in patients with amyotrophic lateral sclerosis
, JOURNAL OF NEURAL ENGINEERING, Vol: 18, ISSN: 1741-2560- Author Web Link
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- Citations: 4
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Journal articleChen C, Yu Y, Sheng X, et al., 2021,
Simultaneous and proportional control of wrist and hand movements by decoding motor unit discharges in real time
, JOURNAL OF NEURAL ENGINEERING, Vol: 18, ISSN: 1741-2560- Author Web Link
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- Citations: 22
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Journal articleVeselic S, Zito C, Farina D, 2021,
Human-Robot Interaction With Robust Prediction of Movement Intention Surpasses Manual Control
, Frontiers in Neurorobotics, Vol: 15Physical human-robot interaction (pHRI) enables a user to interact with a physical robotic device to advance beyond the current capabilities of high-payload and high-precision industrial robots. This paradigm opens up novel applications where a the cognitive capability of a user is combined with the precision and strength of robots. Yet, current pHRI interfaces suffer from low take-up and a high cognitive burden for the user. We propose a novel framework that robustly and efficiently assists users by reacting proactively to their commands. The key insight is to include context- and user-awareness in the controller, improving decision-making on how to assist the user. Context-awareness is achieved by inferring the candidate objects to be grasped in a task or scene and automatically computing plans for reaching them. User-awareness is implemented by facilitating the motion toward the most likely object that the user wants to grasp, as well as dynamically recovering from incorrect predictions. Experimental results in a virtual environment of two degrees of freedom control show the capability of this approach to outperform manual control. By robustly predicting user intention, the proposed controller allows subjects to achieve superhuman performance in terms of accuracy and, thereby, usability.
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Journal articleIbáñez J, Angeli CA, Harkema SJ, et al., 2021,
Recruitment order of motor neurons promoted by epidural stimulation in individuals with spinal cord injury.
, Journal of Applied Physiology, Vol: 131, Pages: 1100-1110, ISSN: 1522-1601Spinal cord epidural stimulation (scES) combined with activity-based training can promote motor function recovery in individuals with motor complete spinal cord injury (SCI). The characteristics of motor neuron recruitment, which influence different aspects of motor control, are still unknown when motor function is promoted by scES. Here, we enrolled five individuals with chronic motor complete SCI implanted with an scES unit to study the recruitment order of motor neurons during standing enabled by scES. We recorded high-density electromyography (HD-EMG) signals on the vastus lateralis muscle and inferred the order of recruitment of motor neurons from the relation between amplitude and conduction velocity of the scES-evoked EMG responses along the muscle fibers. Conduction velocity of scES-evoked responses was modulated over time, whereas stimulation parameters and standing condition remained constant, with average values ranging between 3.0 ± 0.1 and 4.4 ± 0.3 m/s. We found that the human spinal circuitry receiving epidural stimulation can promote both orderly (according to motor neuron size) and inverse trends of motor neuron recruitment, and that the engagement of spinal networks promoting rhythmic activity may favor orderly recruitment trends. Conversely, the different recruitment trends did not appear to be related with time since injury or scES implant, nor to the ability to achieve independent knees extension, nor to the conduction velocity values. The proposed approach can be implemented to investigate the effects of stimulation parameters and training-induced neural plasticity on the characteristics of motor neuron recruitment order, contributing to improve mechanistic understanding and effectiveness of epidural stimulation-promoted motor recovery after SCI.NEW & NOTEWORTHY After motor complete spinal cord injury, the human spinal cord receiving epidural stimulation can promote both orderly and inverse trends o
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Conference paperFree D, Syndergaard I, Pigg A, et al., 2021,
Intermuscular Coherence Within the Upper Limb in Persons With Essential Tremor
, Publisher: WILEY, Pages: S588-S588, ISSN: 0885-3185 -
Journal articleTanzarella S, Muceli S, Santello M, et al., 2021,
Synergistic Organization of Neural Inputs from Spinal Motor Neurons to Extrinsic and Intrinsic Hand Muscles
, JOURNAL OF NEUROSCIENCE, Vol: 41, Pages: 6878-6891, ISSN: 0270-6474- Author Web Link
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- Citations: 17
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Journal articleBräcklein M, Ibáñez J, Barsakcioglu DY, et al., 2021,
The control and training of single motor units in isometric tasks are constrained by a common synaptic input signal
<jats:title>Abstract</jats:title><jats:p>Recent developments in neural interfaces enable the real-time and non-invasive tracking of motor neuron spiking activity. Such novel interfaces provide a promising basis for human motor augmentation by extracting potential high-dimensional control signals directly from the human nervous system. However, it is unclear how flexibly humans can control the activity of individual motor neurones to effectively increase the number of degrees-of-freedom available to coordinate multiple effectors simultaneously. Here, we provided human subjects (N=7) with real-time feedback on the discharge patterns of pairs of motor units (MUs) innervating a single muscle (tibialis anterior) and encouraged them to independently control the MUs by tracking targets in a 2D space. Subjects learned control strategies to achieve the target-tracking task for various combinations of MUs. These strategies rarely corresponded to a volitional control of independent input signals to individual MUs. Conversely, MU activation was consistent with a common input to the MU pair, while individual activation of the MUs in the pair was predominantly achieved by alterations in de-recruitment order that could be explained with history-dependent changes in motor neuron excitability. These results suggest that flexible MU control based on independent synaptic inputs to single MUs is not a simple to learn control strategy.</jats:p>
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Journal articleMouchoux J, Carisi S, Dosen S, et al., 2021,
Artificial perception and semiautonomous control in myoelectric hand prostheses increases performance and decreases effort
, IEEE Transactions on Robotics, Vol: 37, Pages: 1298-1312, ISSN: 1552-3098Dexterous control of upper limb prostheses with multiarticulated wrists/hands is still a challenge due to the limitations of myoelectric man–machine interfaces. Multiple factors limit the overall performance and usability of these interfaces, such as the need to control degrees of freedom sequentially and not concurrently, and the inaccuracies in decoding the user intent from weak or fatigued muscles. In this article, we developed a novel man–machine interface that endows a myoelectric prosthesis (MYO) with artificial perception, estimation of user intention, and intelligent control (MYO–PACE) to continuously support the user with automation while preparing the prosthesis for grasping. We compared the MYO–PACE against state-of-the-art myoelectric control (pattern recognition) in laboratory and clinical tests. For this purpose, eight able-bodied and two amputee individuals performed a standard clinical test consisting of a series of manipulation tasks (portion of the SHAP test), as well as a more complex sequence of transfer tasks in a cluttered scene. In all tests, the subjects not only completed the trials faster using the MYO–PACE but also achieved more efficient myoelectric control. These results demonstrate that the implementation of advanced perception, context interpretation, and autonomous decision-making into active prostheses improves control dexterity. Moreover, it also effectively supports the user by speeding up the preshaping phase of the movement and decreasing muscle use.
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Journal articleGermer CM, Farina D, Elias LA, et al., 2021,
Surface EMG crosstalk quantified at the motor unit population level for muscles of the hand, thigh, and calf
, Journal of Applied Physiology, Vol: 131, Pages: 808-820, ISSN: 1522-1601Crosstalk is an important source of error in interpreting surface electromyography (EMG) signals. Here, we aimed at characterizing crosstalk for three groups of synergistic muscles by the identification of individual motor unit action potentials. Moreover, we explored whether spatial filtering (single and double differential) of the EMG signals influences the level of crosstalk. Three experiments were conducted. Participants (total twenty-five) performed isometric contractions at 10% of the maximal voluntary contraction (MVC) with digit muscles and knee extensors, and at 30% MVC with plantar flexors. High-density surface EMG signals were recorded and decomposed into motor unit spike trains. For each muscle, we quantified the crosstalk induced to neighboring muscles and the level of contamination by the nearby muscle activity. We also estimated the influence of crosstalk on the EMG power spectrum and intermuscular correlation. Most motor units (80%) generated significant crosstalk signals to neighboring muscle EMG in monopolar recording mode, but this proportion decreased with spatial filtering (50% and 42% for single and double differential, respectively). Crosstalk induced overestimations of intermuscular correlation and has a small effect on the EMG power spectrum, which indicates that crosstalk is not reduced with high-pass temporal filtering. Conversely, spatial filtering diminished the crosstalk magnitude and the overestimations of intermuscular correlation, confirming to be an effective and simple technique to reduce crosstalk. This paper presents a new method for the identification and quantification of crosstalk at the motor unit level and clarifies the influence of crosstalk on EMG interpretation for muscles with different anatomy.
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Journal articleMcManus L, Lowery M, Merletti R, et al., 2021,
Consensus for experimental design in electromyography (CEDE) project: Terminology matrix
, Journal of Electromyography and Kinesiology, Vol: 59, ISSN: 1050-6411Consensus on the definition of common terms in electromyography (EMG) research promotes consistency in the EMG literature and facilitates the integration of research across the field. This paper presents a matrix developed within the Consensus for Experimental Design in Electromyography (CEDE) project, providing definitions for terms used in the EMG literature. The definitions for physiological and technical terms that are common in EMG research are included in two tables, with key information on each definition provided in a comment section. A brief outline of some basic principles for recording and analyzing EMG is included in an appendix, to provide researchers new to EMG with background and context for understanding the definitions of physiological and technical terms. This terminology matrix can be used as a reference to aid researchers new to EMG in reviewing the EMG literature.
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Journal articleTottrup L, Atashzar SF, Farina D, et al., 2021,
Altered evoked low-frequency connectivity from SI to ACC following nerve injury in rats
, JOURNAL OF NEURAL ENGINEERING, Vol: 18, ISSN: 1741-2560- Author Web Link
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- Citations: 1
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Journal articleSavic AM, Aliakbaryhosseinabadi S, Blicher JU, et al., 2021,
Online control of an assistive active glove by slow cortical signals in patients with amyotrophic lateral sclerosis
, JOURNAL OF NEURAL ENGINEERING, Vol: 18, ISSN: 1741-2560- Author Web Link
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- Citations: 4
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Journal articleFarina D, Mohammadi A, Adali T, et al., 2021,
Signal Processing for Neurorehabilitation and Assistive Technologies [From the Guest Editors]
, IEEE Signal Processing Magazine, Vol: 38, Pages: 5-7, ISSN: 1053-5888- Cite
- Citations: 5
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Journal articleHolobar A, Farina D, 2021,
Noninvasive Neural Interfacing with Wearable Muscle Sensors: Combining Convolutive Blind Source Separation Methods and Deep Learning Techniques for Neural Decoding
, IEEE Signal Processing Magazine, Vol: 38, Pages: 103-118, ISSN: 1053-5888Neural interfacing is essential for advancing our fundamental understanding of movement neurophysiology and for developing human-machine interaction systems. This can be achieved at different levels of the central nervous system (CNS) and peripheral nervous system (PNS); however, direct neural interfaces with brain and nerve tissues face important challenges and are currently limited to clinical cases of severe motor impairment. Recent advances in electronics and signal processing for recording and analyzing surface electromyographic (sEMG) signals allow for a radically new way of establishing human interfaces by reverse engineering the neural information embedded in the electrical activity of skeletal muscles. This approach provides a window into the spiking activity of motor neurons in the spinal cord. In this article, we present a brief overview of neural interfaces and discuss the properties of multichannel sEMG in comparison to other CNS and PNS recording modalities. We then describe signal processing approaches for neural interfacing from sEMG, with a focus on recent breakthroughs in convolutive blind source separation (BSS) methods and deep learning techniques. When combined, these approaches establish unique noninvasive human-machine interfaces for neurotechnologies, with applications in medical devices and large-scale consumer electronics.
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Journal articleJung MK, Muceli S, Rodrigues C, et al., 2021,
Intramuscular EMG-driven musculoskeletal modelling: towards implanted muscle interfacing in spinal cord injury patients
, IEEE Transactions on Biomedical Engineering, Vol: 69, Pages: 63-74, ISSN: 0018-9294OBJECTIVE: Surface EMG-driven modelling has been proposed as a means to control assistive devices by estimating joint torques. Implanted EMG sensors have several advantages over wearable sensors but provide a more localized information on muscle activity, which may impact torque estimates. Here, we tested and compared the use of surface and intramuscular EMG measurements for the estimation of required assistive joint torques using EMG driven modelling. METHODS: Four healthy subjects and three incomplete spinal cord injury (SCI) patients performed walking trials at varying speeds. Motion capture marker trajectories, surface and intramuscular EMG, and ground reaction forces were measured concurrently. Subject-specific musculoskeletal models were developed for all subjects, and inverse dynamics analysis was performed for all individual trials. EMG-driven modelling based joint torque estimates were obtained from surface and intramuscular EMG. RESULTS: The correlation between the experimental and predicted joint torques was similar when using intramuscular or surface EMG as input to the EMG-driven modelling estimator in both healthy individuals and patients. CONCLUSION: We have provided the first comparison of non-invasive and implanted EMG sensors as input signals for torque estimates in healthy individuals and SCI patients. SIGNIFICANCE: Implanted EMG sensors have the potential to be used as a reliable input for assistive exoskeleton joint torque actuation.
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Journal articleIbanez Pereda J, Alessandro DV, John C R, et al., 2021,
Only the fastest corticospinal fibers contribute to beta corticomuscular coherence
, The Journal of Neuroscience, Vol: 41, Pages: 4867-4879, ISSN: 0270-6474Human corticospinal transmission is commonly studied using brain stimulation. However, this approach is biased to activity in the fastest conducting axons. It is unclear whether conclusions obtained in this context are representative of volitional activity in mild-to-moderate contractions. An alternative to overcome this limitation may be to study the corticospinal transmission of endogenously generated brain activity. Here we investigate in humans (N=19; of either sex), the transmission speeds of cortical beta rhythms (∼20Hz) traveling to arm (first dorsal interosseous) and leg (tibialis anterior) muscles during tonic mild contractions. For this purpose, we propose two improvements for the estimation of cortico-muscular beta transmission delays. First, we show that the cumulant density (cross-covariance) is more accurate than the commonly-used directed coherence to estimate transmission delays in bidirectional systems transmitting band-limited signals. Second, we show that when spiking motor unit activity is used instead of interference electromyography, cortico-muscular transmission delay estimates are unaffected by the shapes of the motor unit action potentials. Applying these improvements, we show that descending cortico-muscular beta transmission is only 1-2ms slower than expected from the fastest corticospinal pathways. In the last part of our work, we show results from simulations using estimated distributions of the conduction velocities for descending axons projecting to lower motoneurons (from macaque histological measurements) to suggest two scenarios that can explain fast cortico-muscular transmission: either only the fastest corticospinal axons selectively transmit beta activity, or else the entire pool does. The implications of these two scenarios for our understanding of corticomuscular interactions are discussed.
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Journal articleHug F, Avrillon S, Del Vecchio A, et al., 2021,
Analysis of motor unit spike trains estimated from high-density surface electromyography is highly reliable across operators
, Journal of Electromyography and Kinesiology, Vol: 58, Pages: 102548-102548, ISSN: 1050-6411There is a growing interest in decomposing high-density surface electromyography (HDsEMG) into motor unit spike trains to improve knowledge on the neural control of muscle contraction. However, the reliability of decomposition approaches is sometimes questioned, especially because they require manual editing of the outputs. We aimed to assess the inter-operator reliability of the identification of motor unit spike trains. Eight operators with varying experience in HDsEMG decomposition were provided with the same data extracted using the convolutive kernel compensation method. They were asked to manually edit them following established procedures. Data included signals from three lower leg muscles and different submaximal intensities. After manual analysis, 126 ± 5 motor units were retained (range across operators: 119-134). A total of 3380 rate of agreement values were calculated (28 pairwise comparisons × 11 contractions/muscles × 4-28 motor units). The median rate of agreement value was 99.6%. Inter-operator reliability was excellent for both mean discharge rate and time at recruitment (intraclass correlation coefficient > 0.99). These results show that when provided with the same decomposed data and the same basic instructions, operators converge toward almost identical results. Our data have been made available so that they can be used for training new operators.
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