scholarly journals Muscle synergies are associated with intermuscular coherence in an isometric upper limb task

2019 ◽  
Author(s):  
Pablo Ortega-Auriol ◽  
Winston D Byblow ◽  
Angus JC McMorland
Keyword(s):  
Functional Connectivity ◽  
Upper Limb ◽  
Physiological Mechanism ◽  
Human Movement ◽  
Muscle Synergies ◽  
Alpha Band ◽  
Muscle Weight ◽  
Cortex Area ◽  
Higher Weights ◽  
Intermuscular Coherence

AbstractTo elucidate the underlying physiological mechanism of muscle synergies, we investigated the functional corticomuscular and intermuscular binding during an isometric upper limb task in 14 healthy participants. Cortical activity was recorded using 32-channel encephalography (EEG) and muscle activity using 16-channel electromyography (EMG). Using non-negative matrix factorization (NMF), we calculated muscle synergies from two different tasks. A preliminary multidirectional task was used to identify synergy preferred directions. A subsequent coherence task, consisting of generating forces isometrically in the synergy PDs, was used to assess the functional connectivity properties of synergies. Functional connectivity was estimated using corticomuscular coherence (CMC) and intermuscular coherence (IMC). Overall, we were able to extract four different synergies from the multidirectional task. A significant alpha band IMC was present consistently in all extracted synergies. Moreover, alpha band IMC was higher between muscles with higher weights within a synergy. In contrast, no significant CMC was found between the motor cortex area and synergy muscles. In addition, there is a relationship between a synergy muscle weight and the level of IMC. Our findings suggest the existence of a consistent shared input between muscles of each synergy. Finally, the existence of a shared input onto synergistic muscles within a synergy supports the idea of neurally-derived muscle synergies that build human movement.

scholarly journals Functional connectivity in neuromuscular system underlying bimanual muscle synergies

2016 ◽  
Author(s):  
Ingmar E. J. de Vries ◽  
Andreas Daffertshofer ◽  
Dick F. Stegeman ◽  
Tjeerd W. Boonstra
Keyword(s):  
Functional Connectivity ◽  
Muscle Activity ◽  
Uncontrolled Manifold ◽  
Emg Activity ◽  
Muscle Synergies ◽  
Neural Pathways ◽  
Beta Band ◽  
Corticomuscular Coherence ◽  
Intermuscular Coherence ◽  
High Coordination

AbstractNeural synchrony has been suggested as mechanism for integrating distributed sensorimotor systems involved in coordinated movement. To test the role of corticomuscular and intermuscular coherence in the formation of bimanual muscle synergies, we experimentally manipulated the degree of coordination between hand muscles by varying the sensitivity of the visual feedback to differences in bilateral force. In 16 healthy participants, cortical activity was measured using 64-channel electroencephalography (EEG) and muscle activity of the flexor pollicis brevis muscle of both hands using 8×8-channel high-density electromyography (HDsEMG). Using the uncontrolled manifold framework, coordination between bilateral forces was quantified by the synergy index RV in the time and frequency domain. Functional connectivity was assed using corticomuscular coherence between muscle activity and cortical source activity and intermuscular coherence between bilateral EMG activity. As expected, bimanual synergies were stronger in the high coordination condition. RV was higher in the high coordination condition in frequencies between 0 and 0.5 Hz, and above 2 Hz. For the 0.5-2 Hz frequency band this pattern was inverted. Corticomuscular coherence in the beta band (16-30 Hz) was maximal in the contralateral motor cortex and was reduced in the high coordination condition. In contrast, intermuscular coherence was observed at 5-12 Hz and increased with bimanual coordination. Within-subject comparisons revealed a negative correlation between RV and corticomuscular coherence and a positive correlation between RV and intermuscular coherence. Our findings suggest two distinct neural pathways: (1) Corticomuscular coherence reflects direct corticospinal projections involved in controlling individual muscles; (2) intermuscular coherence reflects diverging pathways involved in the coordination of multiple muscles.

scholarly journals Fatigue influences the recruitment, but not structure, of muscle synergies

2018 ◽  
Author(s):  
P.A. Ortega-Auriol ◽  
T.F. Besier ◽  
W.D. Byblow ◽  
A.J.C. McMorland
Keyword(s):  
Upper Limb ◽  
Human Movement ◽  
Building Blocks ◽  
Original Data ◽  
Modular Organization ◽  
Muscle Synergies ◽  
Median Frequency ◽  
Emg Amplitude ◽  
Fatigue Development ◽  
Novel Approach

AbstractThe development of fatigue elicits multiple adaptations from the neuromuscular system. Muscle synergies are common patterns of neuromuscular activation that have been proposed as the building blocks of human movement. We wanted to identify possible adaptations of muscle synergies to the development of fatigue in the upper limb. Recent studies have reported that synergy structure remains invariant during the development of fatigue, but these studies did not examine isolated synergies. We propose a novel approach to characterize synergy adaptations to fatigue by taking advantage of the spatial tuning of synergies. This approach allows improved identification of changes to individual synergies that might otherwise be confounded by changing contributions of overlapping synergies. To analyse upper limb synergies we applied non-negative matrix factorization to 14 EMG signals from muscles of 11 participants performing isometric contractions. A preliminary multidirectional task was used to identify synergy directional tuning. A subsequent fatiguing task was designed to fatigue the participants in their synergies’ preferred directions. Both tasks provided virtual reality feedback of the applied force direction and magnitude, and were performed at 40% of each participant’s maximal voluntary force. Five epochs were analysed throughout the fatiguing task to identify progressive changes of EMG amplitude, median frequency, synergy structure, and activation coefficients. Three to four synergies were sufficient to account for the variability contained in the original data. Synergy structure was conserved with fatigue, but interestingly synergy activation coefficients decreased on average by 24.5% with fatigue development. EMG amplitude did not change systematically with fatigue, whereas EMG median frequency consistently decreased across all muscles. These results support the notion of a neuromuscular modular organization as the building blocks of human movement, with adaptations to synergy recruitment occurring with fatigue. When synergy tuning properties are considered, the reduction of activation of muscle synergies may be a reliable marker to identify fatigue.

scholarly journals Postural Synergy-Based Exoskeleton Reproducing Natural Human Movements to Improve Upper Limb Motor Control after Stroke

2020 ◽  
Author(s):  
Chang He ◽  
Cai-Hua Xiong ◽  
Ze-Jian Chen ◽  
Wei Fan ◽  
Xiao-Lin Huang
Keyword(s):  
Motor Control ◽  
Upper Limb ◽  
Degrees Of Freedom ◽  
Response Rate ◽  
Human Movement ◽  
Interaction Force ◽  
Human Anatomy ◽  
Clinical Trial Registration ◽  
Upper Limb Exoskeleton ◽  
Human Movements

Abstract Background: Upper limb exoskeletons have drawn significant attention in neurorehabilitation because of anthropomorphic mechanical structure analogous to human anatomy. Whereas, the training movements are typically underorganized because most exoskeletons only control the movement of the hand in space, without considering rehabilitation of joint motion, particularly inter-joint postural synergy. The purposes of this study were to explore the application of a postural synergy-based exoskeleton (Armule) reproducing natural human movements for robot-assisted neurorehabilitation and to preliminarily assess its effect on patients' upper limb motor control after stroke. Methods: We developed a novel upper limb exoskeleton based on the concept of postural synergy, which provided five degrees of freedom (DOF) , natural human movements of the upper limb. Eight participants with hemiplegia due to a first-ever, unilateral stroke were recruited and included. They participated in exoskeleton therapy sessions 45 minutes/day, 5 days/week for 4 weeks, with passive/active training under anthropomorphic trajectories and postures. The primary outcome was the Fugl-Meyer Assessment for Upper Extremities (FMA-UE). The secondary outcomes were the Action Research Arm Test(ARAT), modified Barthel Index (mBI) , and exoskeleton kinematic as well as interaction force metrics: motion smoothness in the joint space, postural synergy error, interaction force smoothness, and the intent response rate. Results: After the 4-weeks intervention, all subjects showed significant improvements in the following clinical measures: the FMA-UE ( p =0.02), the ARAT ( p =0.003), and the mBI score ( p <0.001). Besides, all subjects showed significant improvements in motion smoothness ( p =0.004), postural synergy error ( p =0.014), interaction force smoothness ( p =0.004), and the intent response rate ( p =0.008). Conclusions: The subjects were well adapted to our device that assisted in completing functional movements with natural human movement characteristics. The results of the preliminary clinical intervention indicate that the Armule exoskeleton improves individuals’ motor control and activities of daily living (ADL) function after stroke, which might be associated with kinematic and interaction force optimization and postural synergy modification during functional tasks. Clinical trial registration: ChiCTR, ChiCTR1900026656; Date of registration: October 17, 2019. http://www.chictr.org.cn/showproj.aspx?proj=44420

scholarly journals Neuro-musculoskeletal Upper Limb in-silico as virtual patient

2021 ◽  
Author(s):  
Mallampalli Kapardi ◽  
Madhav Pithapuram ◽  
Raghu Seshadri Iyengar ◽  
Mandayam Rangayyan Yashaswini ◽  
Avinash Kumar Singh ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Upper Limb ◽  
In Silico ◽  
Neural Control ◽  
Early Stage ◽  
Cervical Spinal Cord ◽  
Human Movement ◽  
Virtual Patient ◽  
Spatio Temporal ◽  
Movement Simulation

Virtual patients and physiologies allow experimentation, design, and early-stage clinical trials in-silico. Virtual patient technology for human movement systems that encompasses musculoskeleton and its neural control are few and far in between. In this work, we present one such neuro-musculoskeletal upper limb in-silico model. This upper limb is both modular in architecture and generates movement as an emergent phenomenon out of a multiscale co-simulation of spinal cord neural control and musculoskeletal dynamics. It is developed on the NEUROiD movement simulation platform that enables a co-simulation of popular neural simulator NEURON and the musculoskeletal simulator OpenSim. In this work, we describe the design and development of the upper limb in a modular fashion, while reusing existing models and modules. We further characterize and demonstrate the use of this model in generating a range of commonly observed movements by means of a spatio temporal stimulation pattern delivered to the cervical spinal cord. We believe this work enables a first and small step towards an in-silico paradigms for understanding upper limb movement, disease pathology, medication, and rehabilitation. Index Terms : co-simulation, in-silico, NEUROiD, neuromusculoskeletal, upper limb, Virtual patient.

scholarly journals Effects of Focal Vibration over Upper Limb Muscles on the Activation of Sensorimotor Cortex Network: An EEG Study

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Wei Li ◽  
Chong Li ◽  
Quan Xu ◽  
Linhong Ji
Keyword(s):  
Upper Limb ◽  
Sensorimotor Cortex ◽  
Biceps Brachii ◽  
Central Area ◽  
Therapeutic Effects ◽  
Relative Power ◽  
Alpha Band ◽  
Beta Band ◽  
Muscle Belly ◽  
Limb Muscles

Studying the therapeutic effects of focal vibration (FV) in neurorehabilitation is the focus of current research. However, it is still not fully understood how FV on upper limb muscles affects the sensorimotor cortex in healthy subjects. To explore this problem, this experiment was designed and conducted, in which FV was applied to the muscle belly of biceps brachii in the left arm. During the experiment, electroencephalography (EEG) was recorded in the following three phases: before FV, during FV, and two minutes after FV. During FV, a significant lower relative power at C3 and C4 electrodes and a significant higher connection strength between five channel pairs (Cz-FC1, Cz-C3, Cz-CP6, C4-FC6, and FC6-CP2) in the alpha band were observed compared to those before FV. After FV, the relative power at C4 in the beta band showed a significant increase compared to its value before FV. The changes of the relative power at C4 in the alpha band had a negative correlation with the relative power of the beta band during FV and with that after FV. The results showed that FV on upper limb muscles could activate the bilateral primary somatosensory cortex and strengthen functional connectivity of the ipsilateral central area (FC1, C3, and Cz) and contralateral central area (CP2, Cz, C4, FC6, and CP6). These results contribute to understanding the effect of FV over upper limb muscles on the brain cortical network.

Prediction of Depression Severity Scores Based on Functional Connectivity and Complexity of the EEG Signal

2020 ◽  
Vol 52 (1) ◽  
pp. 52-60
Author(s):  
Yousef Mohammadi ◽  
Mohammad Hassan Moradi
Keyword(s):  
Functional Connectivity ◽  
Regression Model ◽  
Brain Activity ◽  
Clustering Coefficient ◽  
Eeg Signal ◽  
Alpha Band ◽  
Depression Severity ◽  
Severity Scores ◽  
Severity Prediction ◽  
Severity Of Depression

Background Depression is one of the most common mental disorders and the leading cause of functional disabilities. This study aims to specify whether functional connectivity and complexity of brain activity can predict the severity of depression (Beck Depression Inventory–II scores). Methods Resting-state, eyes-closed EEG data were recorded from 60 depressed patients. A phase synchronization measure was used to estimate functional connectivity between all pairs of the EEG channels in the delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) frequency bands. To quantify the local value of functional connectivity, 2 graph theory metrics, degree, and clustering coefficient (CC), were measured. Moreover, Lempel-Ziv complexity (LZC) and fuzzy entropy (FuzzyEn) were used to measure the complexity of the EEG signal. Results Through correlation analysis, a significant negative relationship was found between graph metrics and depression severity in the alpha band. This association was strongly positive for the complexity measures in alpha and delta bands. Also, the linear regression model represented a substantial performance of depression severity prediction based on EEG features of the alpha band ( r = 0.839; P < .0001, root mean square error score of 7.69). Conclusion We found that the brain activity of patients with depression was related to depression severity. Abnormal brain activity reflects an increase in the severity of depression. The presented regression model provides a quantitative depression severity prediction, which can inform the development of EEG state and exhibit potential desirable application for the medical treatment of the depressive disorder.

scholarly journals Abnormal Access of Axial Vibrotactile Input to Deafferented Somatosensory Cortex in Human Upper Limb Amputees

1997 ◽  
Vol 77 (5) ◽  
pp. 2753-2764 ◽  
Author(s):  
John J. M. Kew ◽  
Peter W. Halligan ◽  
John C. Marshall ◽  
Richard E. Passingham ◽  
JOHN C. Rothwell ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Correlation Analysis ◽  
Somatosensory Cortex ◽  
Upper Limb ◽  
Sensory Input ◽  
Human Subjects ◽  
Phantom Limb ◽  
Vibrotactile Stimulation ◽  
Pectoral Region ◽  
Human Upper Limb

Kew, John J. M., Peter W. Halligan, John C. Marshall, Richard E. Passingham, John C. Rothwell, Michael C. Ridding, C. David Marsden, and David J. Brooks. Abnormal access of axial vibrotactile input to deafferented somatosensory cortex in human upper limb amputees. J. Neurophysiol. 77: 2753–2764, 1997. We studied two human subjects with total deafferentation of one upper limb secondary to traumatic multiple cervical root avulsions. Both subjects developed a phantom limb and underwent elective amputation of the paralyzed, deafferentated limb. Psychophysical study revealed in each subject an area of skin in the pectoral region ipsilateral to the amputation where vibrotactile stimulation (VS) elicited referred sensations (RS) in the phantom limb. Positron emission tomography was then used to measure regional cerebral blood flow changes during VS of the pectoral region ipsilateral to the amputation with RS and during VS of a homologous part of the pectoral region adjacent to the intact arm without RS. A voxel-based correlation analysis was subsequently used to study functional connectivity. VS of the pectoral region adjacent to the intact arm was associated with activation of the dorsal part of the contralateral primary somatosensory cortex (S1) in a position consistent with the S1 trunk area. In contrast, VS of the pectoral region ipsilateral to the amputation with RS was associated with activation of the contralateral S1 that extended from the level of the trunk representation ventrally over distances of 20 and 12 mm, respectively, in the two subjects. The area of S1 activated during VS of the digits in a normal control subject was coextensive with the ventral S1 region abnormally activated during VS of the ectopic phantom representation in the two amputees, suggesting that the deafferented digit or hand/arm area had been activated by sensory input from the pectoral region. Correlation analysis showed an abnormal pattern of intrinsic connectivity within the deafferented S1 hand/arm area of both amputees. In one subject, the deafferented S1 was functionally connected with 3 times as many S1 voxels as the normally afferented S1. This abnormal functional connectivity extended in both the rostrocaudal and ventrodorsal dimensions. The results demonstrate that sensory input delivered to the axial body surface may gain access to the S1 hand/arm area in some humans who have suffered extensive deafferentation of this area. The findings are consistent with the hypothesis that deafferentation of an area of S1 may result in activation of previously dormant inputs from body surfaces represented in immediately adjacent parts of S1. The results also provide evidence that changes in functional connectivity between these adjacent areas of the cortex play a role in the somatotopic reorganization.

scholarly journals Unobtrusive Estimation of Cardiovascular Parameters with Limb Ballistocardiography

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2922 ◽  
Author(s):  
Yang Yao ◽  
Sungtae Shin ◽  
Azin Mousavi ◽  
Chang-Sei Kim ◽  
Lisheng Xu ◽  
...  
Keyword(s):  
Upper Limb ◽  
Lower Limb ◽  
Linear Regression Analysis ◽  
Peripheral Resistance ◽  
Physiological Mechanism ◽  
Multivariate Linear Regression Analysis ◽  
Time Intervals ◽  
Processing Procedure ◽  
Characteristic Features ◽  
The Relationship

This study investigates the potential of the limb ballistocardiogram (BCG) for unobtrusive estimation of cardiovascular (CV) parameters. In conjunction with the reference CV parameters (including diastolic, pulse, and systolic pressures, stroke volume, cardiac output, and total peripheral resistance), an upper-limb BCG based on an accelerometer embedded in a wearable armband and a lower-limb BCG based on a strain gauge embedded in a weighing scale were instrumented simultaneously with a finger photoplethysmogram (PPG). To standardize the analysis, the more convenient yet unconventional armband BCG was transformed into the more conventional weighing scale BCG (called the synthetic weighing scale BCG) using a signal processing procedure. The characteristic features were extracted from these BCG and PPG waveforms in the form of wave-to-wave time intervals, wave amplitudes, and wave-to-wave amplitudes. Then, the relationship between the characteristic features associated with (i) the weighing scale BCG-PPG pair and (ii) the synthetic weighing scale BCG-PPG pair versus the CV parameters, was analyzed using the multivariate linear regression analysis. The results indicated that each of the CV parameters of interest may be accurately estimated by a combination of as few as two characteristic features in the upper-limb or lower-limb BCG, and also that the characteristic features recruited for the CV parameters were to a large extent relevant according to the physiological mechanism underlying the BCG.

scholarly journals Muscle Synergies Reliability in the Power Clean Exercise

2020 ◽  
Vol 5 (4) ◽  
pp. 75
Author(s):  
Paulo D. G. Santos ◽  
João R. Vaz ◽  
Paulo F. Correia ◽  
Maria J. Valamatos ◽  
António P. Veloso ◽  
...  
Keyword(s):  
Nonnegative Matrix Factorization ◽  
Nonnegative Matrix ◽  
Human Movement ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Complex Task ◽  
Muscle Coordination ◽  
High Similarity ◽  
Strength Tests ◽  
Power Clean

Muscle synergy extraction has been utilized to investigate muscle coordination in human movement, namely in sports. The reliability of the method has been proposed, although it has not been assessed previously during a complex sportive task. Therefore, the aim of the study was to evaluate intra- and inter-day reliability of a strength training complex task, the power clean, assessing participants’ variability in the task across sets and days. Twelve unexperienced participants performed four sets of power cleans in two test days after strength tests, and muscle synergies were extracted from electromyography (EMG) data of 16 muscles. Three muscle synergies accounted for almost 90% of variance accounted for (VAF) across sets and days. Intra-day VAF, muscle synergy vectors, synergy activation coefficients and individual EMG profiles showed high similarity values. Inter-day muscle synergy vectors had moderate similarity, while the variables regarding temporal activation were still strongly related. The present findings revealed that the muscle synergies extracted during the power clean remained stable across sets and days in unexperienced participants. Thus, the mathematical procedure for the extraction of muscle synergies through nonnegative matrix factorization (NMF) may be considered a reliable method to study muscle coordination adaptations from muscle strength programs.

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