Challenges and new approaches to proving the existence of muscle synergies of neural origin.

Muscle coordination studies repeatedly show low-dimensionality of muscle activations for a wide variety of motor tasks. The basis vectors of this low-dimensional subspace, termed muscle synergies, are hypothesized to reflect neurally-established functional muscle groupings that simplify body control...

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Autores principales:	Jason J Kutch, Francisco J Valero-Cuevas
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2012
Materias:	Biology (General) QH301-705.5
Acceso en línea:	https://doaj.org/article/bd3bee73d5904175a882dae653459326
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spelling	oai:doaj.org-article:bd3bee73d5904175a882dae6534593262021-11-18T05:51:22ZChallenges and new approaches to proving the existence of muscle synergies of neural origin.1553-734X1553-735810.1371/journal.pcbi.1002434https://doaj.org/article/bd3bee73d5904175a882dae6534593262012-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22570602/?tool=EBIhttps://doaj.org/toc/1553-734Xhttps://doaj.org/toc/1553-7358Muscle coordination studies repeatedly show low-dimensionality of muscle activations for a wide variety of motor tasks. The basis vectors of this low-dimensional subspace, termed muscle synergies, are hypothesized to reflect neurally-established functional muscle groupings that simplify body control. However, the muscle synergy hypothesis has been notoriously difficult to prove or falsify. We use cadaveric experiments and computational models to perform a crucial thought experiment and develop an alternative explanation of how muscle synergies could be observed without the nervous system having controlled muscles in groups. We first show that the biomechanics of the limb constrains musculotendon length changes to a low-dimensional subspace across all possible movement directions. We then show that a modest assumption--that each muscle is independently instructed to resist length change--leads to the result that electromyographic (EMG) synergies will arise without the need to conclude that they are a product of neural coupling among muscles. Finally, we show that there are dimensionality-reducing constraints in the isometric production of force in a variety of directions, but that these constraints are more easily controlled for, suggesting new experimental directions. These counter-examples to current thinking clearly show how experimenters could adequately control for the constraints described here when designing experiments to test for muscle synergies--but, to the best of our knowledge, this has not yet been done.Jason J KutchFrancisco J Valero-CuevasPublic Library of Science (PLoS)articleBiology (General)QH301-705.5ENPLoS Computational Biology, Vol 8, Iss 5, p e1002434 (2012)
institution	DOAJ
collection	DOAJ
language	EN
topic	Biology (General) QH301-705.5
spellingShingle	Biology (General) QH301-705.5 Jason J Kutch Francisco J Valero-Cuevas Challenges and new approaches to proving the existence of muscle synergies of neural origin.
description	Muscle coordination studies repeatedly show low-dimensionality of muscle activations for a wide variety of motor tasks. The basis vectors of this low-dimensional subspace, termed muscle synergies, are hypothesized to reflect neurally-established functional muscle groupings that simplify body control. However, the muscle synergy hypothesis has been notoriously difficult to prove or falsify. We use cadaveric experiments and computational models to perform a crucial thought experiment and develop an alternative explanation of how muscle synergies could be observed without the nervous system having controlled muscles in groups. We first show that the biomechanics of the limb constrains musculotendon length changes to a low-dimensional subspace across all possible movement directions. We then show that a modest assumption--that each muscle is independently instructed to resist length change--leads to the result that electromyographic (EMG) synergies will arise without the need to conclude that they are a product of neural coupling among muscles. Finally, we show that there are dimensionality-reducing constraints in the isometric production of force in a variety of directions, but that these constraints are more easily controlled for, suggesting new experimental directions. These counter-examples to current thinking clearly show how experimenters could adequately control for the constraints described here when designing experiments to test for muscle synergies--but, to the best of our knowledge, this has not yet been done.
format	article
author	Jason J Kutch Francisco J Valero-Cuevas
author_facet	Jason J Kutch Francisco J Valero-Cuevas
author_sort	Jason J Kutch
title	Challenges and new approaches to proving the existence of muscle synergies of neural origin.
title_short	Challenges and new approaches to proving the existence of muscle synergies of neural origin.
title_full	Challenges and new approaches to proving the existence of muscle synergies of neural origin.
title_fullStr	Challenges and new approaches to proving the existence of muscle synergies of neural origin.
title_full_unstemmed	Challenges and new approaches to proving the existence of muscle synergies of neural origin.
title_sort	challenges and new approaches to proving the existence of muscle synergies of neural origin.
publisher	Public Library of Science (PLoS)
publishDate	2012
url	https://doaj.org/article/bd3bee73d5904175a882dae653459326
work_keys_str_mv	AT jasonjkutch challengesandnewapproachestoprovingtheexistenceofmusclesynergiesofneuralorigin AT franciscojvalerocuevas challengesandnewapproachestoprovingtheexistenceofmusclesynergiesofneuralorigin
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Challenges and new approaches to proving the existence of muscle synergies of neural origin.

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