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Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons

Coherence between electromyographic (EMG) signals is often used to infer the common synaptic input to populations of motor neurons. This analysis, however, may be limited due to the filtering effect of the motor unit action potential waveforms. This study investigated the ability of surface EMG–EMG...

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Autores principales: Dideriksen, Jakob L., Negro, Francesco, Falla, Deborah, Kristensen, Signe R., Mrachacz-Kersting, Natalie, Farina, Dario
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004394/
https://www.ncbi.nlm.nih.gov/pubmed/29942254
http://dx.doi.org/10.3389/fnhum.2018.00207
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author Dideriksen, Jakob L.
Negro, Francesco
Falla, Deborah
Kristensen, Signe R.
Mrachacz-Kersting, Natalie
Farina, Dario
author_facet Dideriksen, Jakob L.
Negro, Francesco
Falla, Deborah
Kristensen, Signe R.
Mrachacz-Kersting, Natalie
Farina, Dario
author_sort Dideriksen, Jakob L.
collection PubMed
description Coherence between electromyographic (EMG) signals is often used to infer the common synaptic input to populations of motor neurons. This analysis, however, may be limited due to the filtering effect of the motor unit action potential waveforms. This study investigated the ability of surface EMG–EMG coherence to predict common synaptic input to motor neurons. Surface and intramuscular EMG were recorded from two locations of the tibialis anterior muscle during steady ankle dorsiflexions at 5 and 10% of the maximal force in 10 healthy individuals. The intramuscular EMG signals were decomposed to identify single motor unit spike trains. For each trial, the strength of the common input in different frequency bands was estimated from the coherence between two cumulative spike trains, generated from sets of single motor unit spike trains (reference measure). These coherence values were compared with those obtained from the coherence between the surface EMG signals (raw, rectified, and high-passed filtered at 250 Hz before rectification) using linear regression. Overall, the high-pass filtering of the EMG prior to rectification did not substantially change the results with respect to rectification only. For both signals, the correlation of EMG coherence with motor unit coherence was strong at 5% MVC (r(2) > 0.8; p < 0.01), but only for frequencies > 5 Hz. At 10% MVC, the correlation between EMG and motor unit coherence was only significant for frequencies > 15 Hz (r(2) > 0.8; p < 0.01). However, when using raw EMG for coherence analysis, the only significant relation with motor unit coherence was observed for the bandwidth 5–15 Hz (r(2) > 0.68; p = 0.04). In all cases, there was no association between motor unit and EMG coherence for frequencies < 5 Hz (r(2) ≤ 0.2; p ≥ 0.51). In addition, a substantial error in the best linear fit between motor unit and EMG coherence was always present. In conclusion, high-frequency (>5 Hz) common synaptic inputs to motor neurons can partly be estimated from the rectified surface EMG at low-level steady contractions. The results, however, suggest that this association is weakened with increasing contraction intensity and that input at lower frequencies during steady isometric contractions cannot be detected accurately by surface EMG coherence.
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spelling pubmed-60043942018-06-25 Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons Dideriksen, Jakob L. Negro, Francesco Falla, Deborah Kristensen, Signe R. Mrachacz-Kersting, Natalie Farina, Dario Front Hum Neurosci Neuroscience Coherence between electromyographic (EMG) signals is often used to infer the common synaptic input to populations of motor neurons. This analysis, however, may be limited due to the filtering effect of the motor unit action potential waveforms. This study investigated the ability of surface EMG–EMG coherence to predict common synaptic input to motor neurons. Surface and intramuscular EMG were recorded from two locations of the tibialis anterior muscle during steady ankle dorsiflexions at 5 and 10% of the maximal force in 10 healthy individuals. The intramuscular EMG signals were decomposed to identify single motor unit spike trains. For each trial, the strength of the common input in different frequency bands was estimated from the coherence between two cumulative spike trains, generated from sets of single motor unit spike trains (reference measure). These coherence values were compared with those obtained from the coherence between the surface EMG signals (raw, rectified, and high-passed filtered at 250 Hz before rectification) using linear regression. Overall, the high-pass filtering of the EMG prior to rectification did not substantially change the results with respect to rectification only. For both signals, the correlation of EMG coherence with motor unit coherence was strong at 5% MVC (r(2) > 0.8; p < 0.01), but only for frequencies > 5 Hz. At 10% MVC, the correlation between EMG and motor unit coherence was only significant for frequencies > 15 Hz (r(2) > 0.8; p < 0.01). However, when using raw EMG for coherence analysis, the only significant relation with motor unit coherence was observed for the bandwidth 5–15 Hz (r(2) > 0.68; p = 0.04). In all cases, there was no association between motor unit and EMG coherence for frequencies < 5 Hz (r(2) ≤ 0.2; p ≥ 0.51). In addition, a substantial error in the best linear fit between motor unit and EMG coherence was always present. In conclusion, high-frequency (>5 Hz) common synaptic inputs to motor neurons can partly be estimated from the rectified surface EMG at low-level steady contractions. The results, however, suggest that this association is weakened with increasing contraction intensity and that input at lower frequencies during steady isometric contractions cannot be detected accurately by surface EMG coherence. Frontiers Media S.A. 2018-06-11 /pmc/articles/PMC6004394/ /pubmed/29942254 http://dx.doi.org/10.3389/fnhum.2018.00207 Text en Copyright © 2018 Dideriksen, Negro, Falla, Kristensen, Mrachacz-Kersting and Farina. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Neuroscience
Dideriksen, Jakob L.
Negro, Francesco
Falla, Deborah
Kristensen, Signe R.
Mrachacz-Kersting, Natalie
Farina, Dario
Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons
title Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons
title_full Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons
title_fullStr Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons
title_full_unstemmed Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons
title_short Coherence of the Surface EMG and Common Synaptic Input to Motor Neurons
title_sort coherence of the surface emg and common synaptic input to motor neurons
topic Neuroscience
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004394/
https://www.ncbi.nlm.nih.gov/pubmed/29942254
http://dx.doi.org/10.3389/fnhum.2018.00207
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