The identification of extensive samples of motor units in human muscles reveals diverse effects of neuromodulatory inputs on the rate coding

eLife, Journal Year: 2024, Volume and Issue: 13

Published: Dec. 9, 2024

Movements are performed by motoneurons transforming synaptic inputs into an activation signal that controls muscle force. The control emerges from interactions between ionotropic and neuromodulatory to motoneurons. Critically, these vary across motoneuron pools differ muscles. To provide the most comprehensive framework date of motor unit activity during isometric contractions, we identified firing extensive samples units in tibialis anterior (129 ± 44 per participant; n=8) vastus lateralis (130 63 muscles contractions up 80% maximal From this unique dataset, rate coding each was characterised as relation its instantaneous applied force, with assumption linear increase force reflects a proportional net excitatory received motoneuron. This natural logarithm function comprised two stages. initial stage marked steep acceleration rate, which greater for low- than medium- high-threshold units. second high- low-threshold Changes were largely non-linear ramp-up ramp-down phases task, but significant prolonged only evident medium-threshold Contrary what is usually assumed, our results demonstrate can follow large variety trends pool. neural perspective, findings indicate how use gain transform limited bandwidths intended

Language: Английский

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Greater distal activation of the biceps femoris long head during knee flexion and hip extension tasks reflects differences in peripheral, not central, motor unit properties.

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 16, 2024

Abstract Purpose Recent research has explored region-specific responses within the biceps femoris long head. However, evidence on regional muscle activation remains controversial, primarily because information derived solely from surface electromyograms (sEMG) amplitude does not necessarily provide an accurate estimate of neural drive to muscle. To address this limitation, study investigated whether there are proximodistal differences in motor unit properties head during isometric hip extension and knee flexion tasks. Methods Seventeen resistance-trained males performed tasks at 20% 40% maximal voluntary contraction. High-density sEMG were recorded proximal distal regions decomposed into individual units. Central (mean discharge rate, rate variability, recruitment de-recruitment thresholds) action potential (amplitude conduction velocity) analyzed. Bipolar was also calculated for each region simulate traditional measurements. Results amplitude, velocity significantly greater both In contrast, no observed central properties. Conclusion These findings suggest that increased bipolar is driven by rather than modulation, likely influenced intra-muscular variations mechanics geometry. This emphasizes limitations relying infer control strategies

Language: Английский

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Changes in high-frequency neural inputs to muscles during movement cancellation

Journal of Neural Engineering, Journal Year: 2024, Volume and Issue: 21(5), P. 056039 - 056039

Published: Oct. 1, 2024

Abstract Objective. Cortical beta (13–30 Hz) and gamma (30–60 oscillations are prominent in the motor cortex known to be transmitted muscles despite their limited direct impact on force modulation. However, we currently lack fundamental knowledge about saliency of these at spinal level. Here, developed an experimental approach examine modulations high-frequency inputs motoneurons under different states while maintaining a stable force, thus constraining behaviour. Approach. Specifically, acquired brain muscle activity during ‘GO’/’NO-GO’ task. In this experiment, effector for task (tibialis anterior) was kept tonically active trials, participants ( N = 12) reacted sequences auditory stimuli by either keeping contraction unaltered (‘NO-GO’ trials), or quickly performing ballistic (‘GO’ trials). Motor unit (MU) firing extracted from high-density surface intramuscular electromyographic signals, changes its spectral contents ‘NO-GO’ trials were analysed. Main results. We observed increase low-gamma (30–45 after cue MU population activity. These results line with measured electroencephalography. increases power occur without relevant alterations as behaviour restricted contraction. Significance. show that cortical rhythms also present when subjects cancel prepared action holding This occurs levels produced remain largely unaltered. Our suggest recordings informative not force-control signals. opens up new potential use cases peripheral neural interfaces.

Language: Английский

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The identification of extensive samples of motor units in human muscles reveals diverse effects of neuromodulatory inputs on the rate coding

Published: Nov. 21, 2024

Movements are performed by motoneurons transforming synaptic inputs into an activation signal that controls muscle force. The control emerges from interactions between ionotropic and neuromodulatory to motoneurons. Critically, these vary across motoneuron pools differ muscles. To provide the most comprehensive framework date of motor unit activity during isometric contractions, we identified firing extensive samples units in Tibialis Anterior (129±44 per participant; n=8) Vastus Lateralis (130±63 muscles contractions up 80% maximal From this unique dataset, rate coding each was characterised as relation its instantaneous applied force, with assumption linear increase force reflects a proportional net excitatory received motoneuron. This natural logarithm function comprised two stages. initial stage marked steep acceleration rate, which greater for low- than medium- high-threshold units. second high- low-threshold Changes were largely non-linear ramp-up ramp-down phases task, but significant prolonged only evident medium-threshold Contrary what is usually assumed, our results demonstrate can follow large variety trends pool. neural perspective, findings indicate how use gain transform limited bandwidths intended

Language: Английский

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Adaptive optimization of electromyographic channels for intelligent prosthetic hands based on individual differences

Advances in Mechanical Engineering, Journal Year: 2024, Volume and Issue: 16(12)

Published: Dec. 1, 2024

Intelligent prosthetic hands typically require an increase in the number of acquisition channels to improve gesture recognition accuracy, resulting increased device complexity and cost. However, there are individual differences muscle strength, body mass index, exercise habits. Electromyographic currently use standardized electromyographic channel configurations, which lack adaptability differences. To address these issues, this paper proposes electrode configuration adaptive optimization algorithm, enhances integrates traditional genetic algorithms simulated annealing algorithms, implements solutions for different subjects. Experimental results show that outcomes differ among Compared a single proposed algorithm can adaptively optimize based on while ensuring effectiveness, retaining information significantly contributes classification recognition, meeting stable their motion intentions by

Language: Английский

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