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Slow dynamics of postural sway are in the feedback loop
Tim Kiemel1, Kelvin S Oie, John J Jeka
1Dept. of Kinesiology, University of Maryland, College Park, MD 20742, USA. kiemel@umd.edu
Journal of Neurophysiology
|September 30, 2005
Summary
This study reveals the slow component of postural sway originates within the feedback loop, likely due to state estimation errors. Understanding this slow process is key for improving balance control.
Area of Science:
- Biomechanics
- Human motor control
- Systems neuroscience
Background:
- Postural sway comprises slow and damped-oscillatory components.
- The slow component dominates sway variance during quiet stance.
- The origin of the slow sway component remains unclear.
Purpose of the Study:
- Investigate if the slow postural sway process is internal or external to the feedback loop.
- Determine the mechanistic basis of the slow sway component.
Main Methods:
- Applied sum-of-sines visual motion to standing subjects.
- Utilized linear stochastic models to analyze sway trajectories.
- Quantified sway structure and visual motion transfer functions.
Main Results:
- A fifth-order stochastic model accurately described postural sway.
- The slow sway process was confirmed to be inside the feedback loop.
- Results support state estimation errors as the source of the slow component.
Conclusions:
- The slow component of postural sway arises from internal feedback mechanisms, specifically state estimation.
- This finding clarifies the underlying basis of postural instability.
- Implications for understanding and potentially treating balance disorders.