title: Stochastic two-delay differential model of delayed visual feedback effects on postural dynamics.
abstract: We report on experiments and modelling involving the 'visuo-postural control loop' in the upright stance. We experimentally manipulated an artificial delay to the visual feedback during standing, presented at delays ranging from 0 to 1 s in increments of 250 ms. Using stochastic delay differential equations, we explicitly modelled the centre-of-pressure (COP) and centre-of-mass (COM) dynamics with two independent delay terms for vision and proprioception. A novel 'drifting fixed point' hypothesis was used to describe the fluctuations of the COM with the COP being modelled as a faster, corrective process of the COM. The model was in good agreement with the data in terms of probability density functions, power spectral densities, short- and long-term correlations (Hurst exponents) as well the critical time between the two ranges.
authors.affiliation: Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada. jboul079@uottawa.ca
authors.forename: Jason
authors.initials: J
authors.lastname: Boulet
authors.forename: Ramesh
authors.initials: R
authors.lastname: Balasubramaniam
authors.forename: Andreas
authors.initials: A
authors.lastname: Daffertshofer
authors.forename: André
authors.initials: A
authors.lastname: Longtin
mesh_terms: D000328:Adult; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology*; D013269:Stochastic Processes; D049490:Systems Biology; D013997:Time Factors; D014785:Vision, Ocular / Q000502:physiology; D055815:Young Adult