| Fast visual prediction and slow optimization of preferred walking speed. | |
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MedLine Citation:
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PMID: 22298829 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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People prefer walking speeds that minimize energetic cost. This may be accomplished by directly sensing metabolic rate and adapting gait to minimize it, but only slowly due to the compounded effects of sensing delays and iterative convergence. Visual and other sensory information is available more rapidly and could help predict which gait changes reduce energetic cost, but only approximately because it relies on prior experience and an indirect means to achieve economy. We used virtual reality to manipulate visually presented speed while ten healthy subjects freely walked on a self-paced treadmill to test whether the nervous system beneficially combines these two mechanisms. Rather than manipulating the speed of visual flow directly, we coupled it to the walking speed selected by the subject and then manipulated the ratio between these two speeds. We then quantified the dynamics of walking speed adjustments in response to perturbations of the visual speed. For step changes in visual speed, subjects responded with rapid speed adjustments (lasting <2 sec) and in a direction opposite of the perturbation and consistent with returning the visually presented speed toward their preferred walking speed - when visual speed was suddenly twice (half) the walking speed, subjects decreased (increased) their speed. Subjects did not maintain the new speed but instead gradually returned towards the speed preferred prior to the perturbation (lasting >300 sec). The timing and direction of these responses strongly indicate that a rapid predictive process informed by visual feedback helps select preferred speed, perhaps to complement a slower optimization process that seeks to minimize energetic cost. |
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Authors:
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Shawn Michael Oconnor; J Maxwell Donelan |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-2-1 |
Journal Detail:
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Title: Journal of neurophysiology Volume: - ISSN: 1522-1598 ISO Abbreviation: - Publication Date: 2012 Feb |
Date Detail:
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Created Date: 2012-2-2 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0375404 Medline TA: J Neurophysiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1Simon Fraser University. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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