Publications by authors named "Ivan Vujaklija"

To date, over 40 epigenetic and 300 epitranscriptomic modifications have been identified. However, current short-read sequencing-based experimental methods can detect <10% of these modifications. Integrating long-read sequencing technologies with advanced computational approaches, including statistical analysis and machine learning, offers a promising new frontier to address this challenge.

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Article Synopsis
  • Children with Cerebral Palsy (CP) show less selective and simplified muscle activation while walking due to brain injury and associated muscle changes.
  • A study using high-density surface electromyography (HDsEMG) compared muscle activity in adolescents with CP and typically developed (TD) adolescents during treadmill walking, revealing more uniform muscle activation in CP individuals.
  • Findings indicate that the less structured muscle activation in CP is linked to stronger ankle co-contraction and spasticity, providing insights into motor control deficits and potential improvements from interventions.
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Objective: To describe and evaluate the combination of osseointegration and nerve transfers in 3 transhumeral amputees.

Design: Case series.

Patients: Three male patients with a unilateral traumatic transhumeral amputation.

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. Neural interfacing via decomposition of high-density surface electromyography (HD-sEMG) should be robust to signal non-stationarities incurred by changes in joint pose and contraction intensity..

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An increasing focus on extending automated surface electromyography (EMG) decomposition algorithms to operate under non-stationary conditions requires rigorous and robust validation. However, relevant benchmarks derived manually from iEMG are laborsome to obtain and this is further exacerbated by the need to consider multiple contraction conditions. This work demonstrates a semi-automatic technique for extracting motor units (MUs) whose activities are present in concurrently recorded high-density surface EMG (HD-sEMG) and intramuscular EMG (iEMG) during isometric contractions.

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Introduction: Actuated lower limb prostheses, including powered (active) and semi-active (quasi-passive) joints, are endowed with controllable power and/or impedance, which can be advantageous to limb impairment individuals by improving locomotion mechanics and reducing the overall metabolic cost of ambulation. However, an increasing number of commercial and research-focused options have made navigating this field a daunting task for users, researchers, clinicians, and professionals.

Areas Covered: The present paper provides an overview of the latest trends and developments in the field of actuated lower-limb prostheses and corresponding technologies.

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Unsupervised myocontrol methods aim to create control models for myoelectric prostheses while avoiding the complications of acquiring reliable, regular, and sufficient labeled training data. A limitation of current unsupervised methods is that they fix the number of controlled prosthetic functions a priori, thus requiring an initial assessment of the user's motor skills and neglecting the development of novel motor skills over time.We developed a progressive unsupervised myocontrol (PUM) paradigm in which the user and the control model coadaptively identify distinct muscle synergies, which are then used to control arbitrarily associated myocontrol functions, each corresponding to a hand or wrist movement.

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Objective: Motor unit (MU) discharge timings encode human motor intentions to the finest degree. Whilst tapping into such information can bring significant gains to a range of applications, current approaches to MU decoding from surface signals do not scale well with the demands of dexterous human-machine interfacing (HMI). To optimize the forward estimation accuracy and time-efficiency of such systems, we propose the inclusion of task-wise initialization and MU subset selection.

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Electromyographic signals (EMGs) can provide information on the overall activity of the innervating motor neuros in any given muscle but also globally reflect the underlying neuromechanics of human movement (e.g., muscle synergies).

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Objective: The objective clinical evaluation of user's capabilities to handle their prosthesis is done using various tests which primarily focus on the task completion speed and do not explicitly account for the potential presence of compensatory motions. Given that the excessive body compensation is a common indicator of inadequate prosthesis control, tests which include subjective observations on the quality of performed motions have been introduced. However, these metrics are then influenced by the examiner's opinions, skills, and training making them harder to standardize across patient pools and compare across different prosthetic technologies.

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Unlabelled: Achieving robust, intuitive, simultaneous and proportional control over multiple degrees of freedom (DOFs) is an outstanding challenge in the development of myoelectric prosthetic systems. Since the priority in myoelectric prosthesis solutions is robustness and stability, their number of functions is usually limited.

Objective: Here, we introduce a system for intuitive concurrent hand and wrist control, based on a robust feature-extraction protocol and machine-learning.

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. Neural interfaces need to become more unobtrusive and socially acceptable to appeal to general consumers outside rehabilitation settings..

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Article Synopsis
  • - This study introduces a myoelectric interface called the unsupervised adaptive myocontrol (UAM), which learns and adapts in real time to user movements by extracting motor control patterns from multiple muscle signals without needing explicit labels.
  • - UAM was tested with able-bodied and amputee subjects in virtual target-reaching tasks and practical tasks like moving clothespins, demonstrating better performance and resilience against electrode displacement compared to traditional myocontrol systems.
  • - The results show that UAM maintains consistent control performance even when conditions change, providing a robust and practical solution for bionic interfaces in clinical settings that blends neuromuscular principles with online learning capabilities.
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Joint torques of lower extremity are important clinical indicators of gait capability. This parameter can be quantified via hybrid neuromusculoskeletal modelling that combines electromyography-driven modelling and static optimisation. The simulations rely on kinematics and external force measurements, for example, ground reaction forces (GRF) and the corresponding centres of pressure (COP), which are conventionally acquired using force plates.

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Article Synopsis
  • Most prosthetic limbs can move autonomously but are often not recognized by users as part of their body.
  • Current technology limits the connection and communication between robotic limbs and the user, hindering performance.
  • The article suggests that using osseointegration, improved neural signal amplification, and sensory feedback can enhance bionic limbs, promoting their clinical adoption with proper redesign and rehabilitation.
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Brachial plexus injuries with multiple-root involvement lead to severe and long-lasting impairments in the functionality and appearance of the affected upper extremity. In cases, where biologic reconstruction of hand and arm function is not possible, bionic reconstruction may be considered as a viable clinical option. Bionic reconstruction, through a careful combination of surgical augmentation, amputation, and prosthetic substitution of the functionless hand, has been shown to achieve substantial improvements in function and quality of life.

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Motivation: Motif-HMM (mHMM) scanning has been shown to possess unique advantages over standardly used sequence-profile search methods (e.g. HMMER, PSI-BLAST) since it is particularly well-suited to discriminate proteins with variations inside conserved motifs (e.

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Non-negative Matrix Factorization (NMF) has been effective in extracting commands from surface electromyography (EMG) for the control of upper-limb prostheses. This approach enables Simultaneous and Proportional Control (SPC) over multiple degrees-of-freedom (DoFs) in a minimally supervised way. Here, like with other myoelectric approaches, robustness remains essential for clinical adoption, with device donning/doffing being a known cause for performance degradation.

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Conventional myoelectric controllers provide a mapping between electromyographic signals and prosthetic functions. However, due to a number of instabilities continuously challenging this process, an initial mapping may require an extended calibration phase with long periods of user-training in order to ensure satisfactory performance. Recently, studies on co-adaptation have highlighted the benefits of concurrent user learning and machine adaptation where systems can cope with deficiencies in the initial model by learning from newly acquired data.

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Background: Current myoelectric control algorithms for active prostheses map time- and frequency-domain features of the interference EMG signal into prosthesis commands. With this approach, only a fraction of the available information content of the EMG is used and the resulting control fails to satisfy the majority of users. In this study, we predict joint angles of the three degrees of freedom of the wrist from motor unit discharge timings identified by decomposition of high-density surface EMG.

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Selective nerve transfers surgically rewire motor neurons and are used in extremity reconstruction to restore muscle function or to facilitate intuitive prosthetic control. We investigated the neurophysiological effects of rewiring motor axons originating from spinal motor neuron pools into target muscles with lower innervation ratio in a rat model. Following reinnervation, the target muscle's force regenerated almost completely, with the motor unit population increasing to 116% in functional and 172% in histological assessments with subsequently smaller muscle units.

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Objective: The aim of the study was to report normative outcome data of prosthetic hand function in below-elbow amputees using four different objective measurements closely related to activities of daily living.

Design: Seventeen patients who underwent prosthetic fitting after unilateral below-elbow amputation were enrolled in this study. Global upper extremity function was evaluated using the Action Research Arm Test, Southampton Hand Assessment Procedure, the Clothespin-Relocation Test, and the Box and Block Test, which monitor hand and extremity function.

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