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Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance

External perturbation forces may compromise standing balance. The nervous system can intervene only after a delay greater than 100 ms, during which the body falls freely. With ageing, sensorimotor delays are prolonged, posing a critical threat to balance. We study a generic model of stabilisation wi...

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Detalles Bibliográficos
Autores principales: Le Mouel, Charlotte, Brette, Romain
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6897426/
https://www.ncbi.nlm.nih.gov/pubmed/31756199
http://dx.doi.org/10.1371/journal.pcbi.1007463
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author Le Mouel, Charlotte
Brette, Romain
author_facet Le Mouel, Charlotte
Brette, Romain
author_sort Le Mouel, Charlotte
collection PubMed
description External perturbation forces may compromise standing balance. The nervous system can intervene only after a delay greater than 100 ms, during which the body falls freely. With ageing, sensorimotor delays are prolonged, posing a critical threat to balance. We study a generic model of stabilisation with neural delays to understand how the organism should adapt to challenging balance conditions. The model suggests that ankle stiffness should be increased in anticipation of perturbations, for example by muscle co-contraction, so as to slow down body fall during the neural response delay. Increased ankle muscle co-contraction is indeed observed in young adults when standing in challenging balance conditions, and in older relative to young adults during normal stance. In parallel, the analysis of the model shows that increases in either stiffness or neural delay must be coordinated with decreases in spinal sensorimotor gains, otherwise the feedback itself becomes destabilizing. Accordingly, a decrease in spinal feedback is observed in challenging conditions, and with age-related increases in neural delay. These observations have been previously interpreted as indicating an increased reliance on cortical rather than spinal control of balance, despite the fact that cortical responses have a longer latency. Our analysis challenges this interpretation by showing that these observations are consistent with a functional coadaptation of spinal feedback gains to functional changes in stiffness and neural delay.
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spelling pubmed-68974262019-12-13 Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance Le Mouel, Charlotte Brette, Romain PLoS Comput Biol Research Article External perturbation forces may compromise standing balance. The nervous system can intervene only after a delay greater than 100 ms, during which the body falls freely. With ageing, sensorimotor delays are prolonged, posing a critical threat to balance. We study a generic model of stabilisation with neural delays to understand how the organism should adapt to challenging balance conditions. The model suggests that ankle stiffness should be increased in anticipation of perturbations, for example by muscle co-contraction, so as to slow down body fall during the neural response delay. Increased ankle muscle co-contraction is indeed observed in young adults when standing in challenging balance conditions, and in older relative to young adults during normal stance. In parallel, the analysis of the model shows that increases in either stiffness or neural delay must be coordinated with decreases in spinal sensorimotor gains, otherwise the feedback itself becomes destabilizing. Accordingly, a decrease in spinal feedback is observed in challenging conditions, and with age-related increases in neural delay. These observations have been previously interpreted as indicating an increased reliance on cortical rather than spinal control of balance, despite the fact that cortical responses have a longer latency. Our analysis challenges this interpretation by showing that these observations are consistent with a functional coadaptation of spinal feedback gains to functional changes in stiffness and neural delay. Public Library of Science 2019-11-22 /pmc/articles/PMC6897426/ /pubmed/31756199 http://dx.doi.org/10.1371/journal.pcbi.1007463 Text en © 2019 Le Mouel, Brette 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
Le Mouel, Charlotte
Brette, Romain
Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
title Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
title_full Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
title_fullStr Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
title_full_unstemmed Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
title_short Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
title_sort anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6897426/
https://www.ncbi.nlm.nih.gov/pubmed/31756199
http://dx.doi.org/10.1371/journal.pcbi.1007463
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