Human Balance Control: Dead Zones, Intermittency, and Micro-chaos

Milton, John; Insperger, Tamás; Stépàn, Gábor

doi:10.1007/978-4-431-55444-8_1

Cited by 13 publications

(12 citation statements)

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“…Indeed the transition between two attractors in DDEs typically takes multiple steps because any solutions with close initial conditions can be on opposite sides of the boundary between the two attractors [23,59,63]. The duration for the transiently stabilized state observed for (1.8) is an order of magnitude shorter than observed for (1.6) [31,54]. Presumably, as the number of thresholds to be negotiated increases (e.g., one each for θ,θ,θ), the duration of the transiently stabilized state becomes longer and longer.…”

Section: Semidiscretization: 0 < R < ∞mentioning

confidence: 95%

Semidiscretization for Time-Delayed Neural Balance Control

Insperger¹,

Milton²,

Stépàn³

2015

SIAM J. Appl. Dyn. Syst.

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Abstract. The observation that time-delayed feedback can stabilize an inverted pendulum motivates the formulation of models of human balance control in terms of delay differential equations (DDEs). Recently the intermittent, digital-like nature of the neural feedback control of balance has become evident. Here, semidiscretization methods for DDEs are used to investigate an unstable dynamic system subjected to a digital controller in the context of a switching model for postural control. In addition to limit cycle and chaotic ("microchaos") oscillations, transiently stabilized balance states are possible even though both the open-loop and the closed-loop systems are globally unstable. The possibility that falls can be an intrinsic component of neural control of balance may provide new insights into how the risk of falling in the elderly can be minimized.

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Section: Semidiscretization: 0 < R < ∞mentioning

confidence: 95%

Semidiscretization for Time-Delayed Neural Balance Control

Insperger¹,

Milton²,

Stépàn³

2015

SIAM J. Appl. Dyn. Syst.

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“…It is likely that all sensory receptors possess a dead zone, namely a threshold below which changes in input are not reflected by changes in output [50]. Usually, the dead zone is very small and hence the presence of lowamplitude oscillations and microchaos is buried within the intrinsic noisy variability.…”

Section: Discussionmentioning

confidence: 99%

Control at stability's edge minimizes energetic costs: expert stick balancing

Milton

Meyer

Zhvanetsky

et al. 2016

J. R. Soc. Interface.

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Stick balancing on the fingertip is a complex voluntary motor task that requires the stabilization of an unstable system. For seated expert stick balancers, the time delay is 0.23 s, the shortest stick that can be balanced for 240 s is 0.32 m and there is a % 0:88 dead zone for the estimation of the vertical displacement angle in the saggital plane. These observations motivate a switching-type, pendulum -cart model for balance control which uses an internal model to compensate for the time delay by predicting the sensory consequences of the stick's movements. Numerical simulations using the semi-discretization method suggest that the feedback gains are tuned near the edge of stability. For these choices of the feedback gains, the cost function which takes into account the position of the fingertip and the corrective forces is minimized. Thus, expert stick balancers optimize control with a combination of quick manoeuvrability and minimum energy expenditures.

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“…The transition matrix, P, of the postural sway is irreducible by the construction 23 and aperiodic by its nature 70 . Note that the transition matrix, P, is an approximation of the Perron-Frobenius operator.…”

Section: Competing Interestsmentioning

confidence: 99%

Free Energy Principle in Human Postural Control System: Skin Stretch Feedback Reduces the Entropy

Hur

Pan

DeBuys

2019

Preprint

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Human upright standing involves an integration of multiple sensory inputs such as vision, vestibular and somatosensory systems. It has been known that sensory deficits worsen the standing balance. However, how the modulation of sensory information contributes to postural stabilization still remains an open question for researchers. The purpose of this work was to formulate the human standing postural control system in the framework of the free-energy principle, and to investigate the efficacy of the skin stretch feedback in enhancing the human standing balance. Previously, we have shown that sensory augmentation by skin stretch feedback at the fingertip could modulate the standing balance of the people with simulated sensory deficits. In this study, subjects underwent ten 30-second trials of quiet standing balance with and without skin stretch feedback. Visual and vestibular sensory deficits were simulated by having each subject close their eyes and tilt their head back. We found that sensory augmentation by velocity-based skin stretch feedback at the fingertip reduced the entropy of the standing postural sway of the people with simulated sensory deficits. This result aligns with the framework of the free energy principle which states that a self-organizing biological system at its equilibrium state tries to minimize its free energy either by updating the internal state or by correcting body movement with appropriate actions. The velocity-based skin stretch feedback at the fingertip may increase the signal-to-noise ratio of the sensory signals, which in turn enhances the accuracy of the internal states in the central nervous system. With more accurate internal states, the human postural control system can further adjust the standing posture to minimize the entropy, and thus the free energy.

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Human Balance Control: Dead Zones, Intermittency, and Micro-chaos

Cited by 13 publications

References 100 publications

Semidiscretization for Time-Delayed Neural Balance Control

Semidiscretization for Time-Delayed Neural Balance Control

Control at stability's edge minimizes energetic costs: expert stick balancing

Free Energy Principle in Human Postural Control System: Skin Stretch Feedback Reduces the Entropy

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