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How Variability and Effort Determine Coordination at Large Forces

Motor control is a challenging task for the central nervous system, since it involves redundant degrees of freedom, nonlinear dynamics of actuators and limbs, as well as noise. When an action is carried out, which factors does your nervous system consider to determine the appropriate set of muscle f...

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Detalles Bibliográficos
Autores principales: Kolossiatis, Michalis, Charalambous, Themistoklis, Burdet, Etienne
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4774921/
https://www.ncbi.nlm.nih.gov/pubmed/26934193
http://dx.doi.org/10.1371/journal.pone.0149512
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author Kolossiatis, Michalis
Charalambous, Themistoklis
Burdet, Etienne
author_facet Kolossiatis, Michalis
Charalambous, Themistoklis
Burdet, Etienne
author_sort Kolossiatis, Michalis
collection PubMed
description Motor control is a challenging task for the central nervous system, since it involves redundant degrees of freedom, nonlinear dynamics of actuators and limbs, as well as noise. When an action is carried out, which factors does your nervous system consider to determine the appropriate set of muscle forces between redundant degrees-of-freedom? Important factors determining motor output likely encompass effort and the resulting motor noise. However, the tasks used in many previous motor control studies could not identify these two factors uniquely, as signal-dependent noise monotonically increases as a function of the effort. To address this, a recent paper introduced a force control paradigm involving one finger in each hand that can disambiguate these two factors. It showed that the central nervous system considers both force noise and amplitude, with a larger weight on the absolute force and lower weights on both noise and normalized force. While these results are valid for the relatively low force range considered in that paper, the magnitude of the force shared between the fingers for large forces is not known. This paper investigates this question experimentally, and develops an appropriate Markov chain Monte Carlo method in order to estimate the weightings given to these factors. Our results demonstrate that the force sharing strongly depends on the force level required, so that for higher force levels the normalized force is considered as much as the absolute force, whereas the role of noise minimization becomes negligible.
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spelling pubmed-47749212016-03-10 How Variability and Effort Determine Coordination at Large Forces Kolossiatis, Michalis Charalambous, Themistoklis Burdet, Etienne PLoS One Research Article Motor control is a challenging task for the central nervous system, since it involves redundant degrees of freedom, nonlinear dynamics of actuators and limbs, as well as noise. When an action is carried out, which factors does your nervous system consider to determine the appropriate set of muscle forces between redundant degrees-of-freedom? Important factors determining motor output likely encompass effort and the resulting motor noise. However, the tasks used in many previous motor control studies could not identify these two factors uniquely, as signal-dependent noise monotonically increases as a function of the effort. To address this, a recent paper introduced a force control paradigm involving one finger in each hand that can disambiguate these two factors. It showed that the central nervous system considers both force noise and amplitude, with a larger weight on the absolute force and lower weights on both noise and normalized force. While these results are valid for the relatively low force range considered in that paper, the magnitude of the force shared between the fingers for large forces is not known. This paper investigates this question experimentally, and develops an appropriate Markov chain Monte Carlo method in order to estimate the weightings given to these factors. Our results demonstrate that the force sharing strongly depends on the force level required, so that for higher force levels the normalized force is considered as much as the absolute force, whereas the role of noise minimization becomes negligible. Public Library of Science 2016-03-02 /pmc/articles/PMC4774921/ /pubmed/26934193 http://dx.doi.org/10.1371/journal.pone.0149512 Text en © 2016 Kolossiatis et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Kolossiatis, Michalis
Charalambous, Themistoklis
Burdet, Etienne
How Variability and Effort Determine Coordination at Large Forces
title How Variability and Effort Determine Coordination at Large Forces
title_full How Variability and Effort Determine Coordination at Large Forces
title_fullStr How Variability and Effort Determine Coordination at Large Forces
title_full_unstemmed How Variability and Effort Determine Coordination at Large Forces
title_short How Variability and Effort Determine Coordination at Large Forces
title_sort how variability and effort determine coordination at large forces
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4774921/
https://www.ncbi.nlm.nih.gov/pubmed/26934193
http://dx.doi.org/10.1371/journal.pone.0149512
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