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Visual field motion during a body pull affects compensatory standing and stepping responses

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St George, RJ ORCID: 0000-0001-6206-1069, Di Giulio, I and Day, BL 2020 , 'Visual field motion during a body pull affects compensatory standing and stepping responses' , Journal of Physiology , doi: 10.1113/JP275436.

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Abstract

The aim of this study was to determine how visual motion evoked by an upper bodyperturbation during standing affects compensatory postural responses. This wasinvestigated by rotating the visual field forwards or backwards about the ankle, time-lockedto a forwards or backwards shoulder pull. Kinematic, kinetic and electromyographicresponses were recorded to a range of pull forces over 160 trials in 12 healthy adults (mean= 31 years, S.D. =5.8). Stepping threshold forces and in-place postural responses werecompared between conditions.When the visual field moved in the same direction as the pull, so that the apparentvelocity of the body was reduced (SLOW condition), the pull-force required to induce a stepwas less than when the visual field either rotated in the opposite direction (FAST) or wasunaltered (NATURAL). For in-place responses, the body was displaced further in thedirection of the pull in the SLOW condition. This was due to a reduction in the resistive forcefrom lower leg muscles 130ms after the visual motion onset. In trials with no pull, the visualmotion induced postural responses that were later (290ms) and had smaller amplitudescompared to when visual motion is paired with an unexpected perturbation of the body.The results suggest that the apparent speed of the visual environment during aperturbation does influence whether a compensatory step is taken, not via a direct effect onthe decision to step but by modulating the initial in-place response.

Item Type: Article
Authors/Creators:St George, RJ and Di Giulio, I and Day, BL
Keywords: Vision, balance, perturbation, stepping, optic flow, automatic postural response
Journal or Publication Title: Journal of Physiology
Publisher: Cambridge Univ Press
ISSN: 0022-3751
DOI / ID Number: 10.1113/JP275436
Copyright Information:

Copyright 2020 The Authors. This is the peer reviewed version of the following article: St George, RJ and Di Giulio, I and Day, BL, Visual field motion during a body pull affects compensatory standing and stepping responses, Journal of Physiology ISSN 0022-3751 (2020). This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article has been published in final form at: http://dx.doi.org/10.1113/JP275436

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