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Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations

The control architecture underlying human reaching has been established, at least in broad outline. However, despite extensive research, the control architecture underlying human locomotion remains unclear. Some studies show evidence of high-level control focused on lower-limb trajectories; others s...

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Autores principales: Ahn, Jooeun, Hogan, Neville
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3313976/
https://www.ncbi.nlm.nih.gov/pubmed/22479311
http://dx.doi.org/10.1371/journal.pone.0031767
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author Ahn, Jooeun
Hogan, Neville
author_facet Ahn, Jooeun
Hogan, Neville
author_sort Ahn, Jooeun
collection PubMed
description The control architecture underlying human reaching has been established, at least in broad outline. However, despite extensive research, the control architecture underlying human locomotion remains unclear. Some studies show evidence of high-level control focused on lower-limb trajectories; others suggest that nonlinear oscillators such as lower-level rhythmic central pattern generators (CPGs) play a significant role. To resolve this ambiguity, we reasoned that if a nonlinear oscillator contributes to locomotor control, human walking should exhibit dynamic entrainment to periodic mechanical perturbation; entrainment is a distinctive behavior of nonlinear oscillators. Here we present the first behavioral evidence that nonlinear neuro-mechanical oscillators contribute to the production of human walking, albeit weakly. As unimpaired human subjects walked at constant speed, we applied periodic torque pulses to the ankle at periods different from their preferred cadence. The gait period of 18 out of 19 subjects entrained to this mechanical perturbation, converging to match that of the perturbation. Significantly, entrainment occurred only if the perturbation period was close to subjects' preferred walking cadence: it exhibited a narrow basin of entrainment. Further, regardless of the phase within the walking cycle at which perturbation was initiated, subjects' gait synchronized or phase-locked with the mechanical perturbation at a phase of gait where it assisted propulsion. These results were affected neither by auditory feedback nor by a distractor task. However, the convergence to phase-locking was slow. These characteristics indicate that nonlinear neuro-mechanical oscillators make at most a modest contribution to human walking. Our results suggest that human locomotor control is not organized as in reaching to meet a predominantly kinematic specification, but is hierarchically organized with a semi-autonomous peripheral oscillator operating under episodic supervisory control.
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spelling pubmed-33139762012-04-04 Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations Ahn, Jooeun Hogan, Neville PLoS One Research Article The control architecture underlying human reaching has been established, at least in broad outline. However, despite extensive research, the control architecture underlying human locomotion remains unclear. Some studies show evidence of high-level control focused on lower-limb trajectories; others suggest that nonlinear oscillators such as lower-level rhythmic central pattern generators (CPGs) play a significant role. To resolve this ambiguity, we reasoned that if a nonlinear oscillator contributes to locomotor control, human walking should exhibit dynamic entrainment to periodic mechanical perturbation; entrainment is a distinctive behavior of nonlinear oscillators. Here we present the first behavioral evidence that nonlinear neuro-mechanical oscillators contribute to the production of human walking, albeit weakly. As unimpaired human subjects walked at constant speed, we applied periodic torque pulses to the ankle at periods different from their preferred cadence. The gait period of 18 out of 19 subjects entrained to this mechanical perturbation, converging to match that of the perturbation. Significantly, entrainment occurred only if the perturbation period was close to subjects' preferred walking cadence: it exhibited a narrow basin of entrainment. Further, regardless of the phase within the walking cycle at which perturbation was initiated, subjects' gait synchronized or phase-locked with the mechanical perturbation at a phase of gait where it assisted propulsion. These results were affected neither by auditory feedback nor by a distractor task. However, the convergence to phase-locking was slow. These characteristics indicate that nonlinear neuro-mechanical oscillators make at most a modest contribution to human walking. Our results suggest that human locomotor control is not organized as in reaching to meet a predominantly kinematic specification, but is hierarchically organized with a semi-autonomous peripheral oscillator operating under episodic supervisory control. Public Library of Science 2012-03-27 /pmc/articles/PMC3313976/ /pubmed/22479311 http://dx.doi.org/10.1371/journal.pone.0031767 Text en Ahn, Hogan. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Ahn, Jooeun
Hogan, Neville
Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations
title Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations
title_full Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations
title_fullStr Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations
title_full_unstemmed Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations
title_short Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations
title_sort walking is not like reaching: evidence from periodic mechanical perturbations
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3313976/
https://www.ncbi.nlm.nih.gov/pubmed/22479311
http://dx.doi.org/10.1371/journal.pone.0031767
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