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Non-linear stimulus-response behavior of the human stance control system is predicted by optimization of a system with sensory and motor noise.

van der Kooij H, Peterka RJ - J Comput Neurosci (2010)

Bottom Line: Different combinations of internal sensory and/or motor noise sources were added to the model to identify the properties of noise sources that were able to account for the experimental remnant sway characteristics.Robust findings were that remnant sway characteristics were best predicted by models that included both sensory and motor noise, the graviceptive noise magnitude was about ten times larger than the proprioceptive noise, and noise sources with signal-dependent properties provided better explanations of remnant sway.Overall results indicate that humans dynamically weight sensory system contributions to stance control and tune their corrective responses to minimize the energetic effects of sensory noise and external stimuli.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomechanical Engineering, University of Twente, 7500 AE, Enschede, The Netherlands. H.vanderKooij@utwente.nl

ABSTRACT
We developed a theory of human stance control that predicted (1) how subjects re-weight their utilization of proprioceptive and graviceptive orientation information in experiments where eyes closed stance was perturbed by surface-tilt stimuli with different amplitudes, (2) the experimentally observed increase in body sway variability (i.e. the "remnant" body sway that could not be attributed to the stimulus) with increasing surface-tilt amplitude, (3) neural controller feedback gains that determine the amount of corrective torque generated in relation to sensory cues signaling body orientation, and (4) the magnitude and structure of spontaneous body sway. Responses to surface-tilt perturbations with different amplitudes were interpreted using a feedback control model to determine control parameters and changes in these parameters with stimulus amplitude. Different combinations of internal sensory and/or motor noise sources were added to the model to identify the properties of noise sources that were able to account for the experimental remnant sway characteristics. Various behavioral criteria were investigated to determine if optimization of these criteria could predict the identified model parameters and amplitude-dependent parameter changes. Robust findings were that remnant sway characteristics were best predicted by models that included both sensory and motor noise, the graviceptive noise magnitude was about ten times larger than the proprioceptive noise, and noise sources with signal-dependent properties provided better explanations of remnant sway. Overall results indicate that humans dynamically weight sensory system contributions to stance control and tune their corrective responses to minimize the energetic effects of sensory noise and external stimuli.

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(a) The body-sway variability can be decomposed into a part that is evoked by the stimulus and into the remnant sway that is not directly attributable to the applied stimulus (Appendix A). Both the experimental stimulus-evoked and remnant body sway increased with stimulus amplitude (mean values across the 8 subjects are shown). (b) The power spectral density of the body sway remnant decreased with increasing frequency and increased with increasing stimulus amplitude. At the excited frequencies (the odd-harmonic frequencies of the fundamental 0.017 Hz frequency), the power was typically higher than at the adjacent non-excited, even-harmonic frequencies
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Fig4: (a) The body-sway variability can be decomposed into a part that is evoked by the stimulus and into the remnant sway that is not directly attributable to the applied stimulus (Appendix A). Both the experimental stimulus-evoked and remnant body sway increased with stimulus amplitude (mean values across the 8 subjects are shown). (b) The power spectral density of the body sway remnant decreased with increasing frequency and increased with increasing stimulus amplitude. At the excited frequencies (the odd-harmonic frequencies of the fundamental 0.017 Hz frequency), the power was typically higher than at the adjacent non-excited, even-harmonic frequencies

Mentions: As shown in Fig. 4(a), both the remnant sway and the stimulus-evoked sway increased with increasing stimulus amplitude. The frequency distributions of the remnant sway are represented by the family of power spectra shown in Fig. 4(b). The remnant PSD values at each individual frequency generally increased with increasing stimulus amplitude and the sets of PSD values corresponding to the different stimulus amplitudes maintained similar shapes across the frequency range when plotted on log-log scales. The PSDs generally decreased in magnitude with increasing frequency. For frequencies below about 0.3 Hz, the PSDs decreased approximately in proportion to f-1, and for frequencies above about 0.7 Hz there was a steeper decrease that was approximately proportional to f-4.Fig. 4


Non-linear stimulus-response behavior of the human stance control system is predicted by optimization of a system with sensory and motor noise.

van der Kooij H, Peterka RJ - J Comput Neurosci (2010)

(a) The body-sway variability can be decomposed into a part that is evoked by the stimulus and into the remnant sway that is not directly attributable to the applied stimulus (Appendix A). Both the experimental stimulus-evoked and remnant body sway increased with stimulus amplitude (mean values across the 8 subjects are shown). (b) The power spectral density of the body sway remnant decreased with increasing frequency and increased with increasing stimulus amplitude. At the excited frequencies (the odd-harmonic frequencies of the fundamental 0.017 Hz frequency), the power was typically higher than at the adjacent non-excited, even-harmonic frequencies
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3108015&req=5

Fig4: (a) The body-sway variability can be decomposed into a part that is evoked by the stimulus and into the remnant sway that is not directly attributable to the applied stimulus (Appendix A). Both the experimental stimulus-evoked and remnant body sway increased with stimulus amplitude (mean values across the 8 subjects are shown). (b) The power spectral density of the body sway remnant decreased with increasing frequency and increased with increasing stimulus amplitude. At the excited frequencies (the odd-harmonic frequencies of the fundamental 0.017 Hz frequency), the power was typically higher than at the adjacent non-excited, even-harmonic frequencies
Mentions: As shown in Fig. 4(a), both the remnant sway and the stimulus-evoked sway increased with increasing stimulus amplitude. The frequency distributions of the remnant sway are represented by the family of power spectra shown in Fig. 4(b). The remnant PSD values at each individual frequency generally increased with increasing stimulus amplitude and the sets of PSD values corresponding to the different stimulus amplitudes maintained similar shapes across the frequency range when plotted on log-log scales. The PSDs generally decreased in magnitude with increasing frequency. For frequencies below about 0.3 Hz, the PSDs decreased approximately in proportion to f-1, and for frequencies above about 0.7 Hz there was a steeper decrease that was approximately proportional to f-4.Fig. 4

Bottom Line: Different combinations of internal sensory and/or motor noise sources were added to the model to identify the properties of noise sources that were able to account for the experimental remnant sway characteristics.Robust findings were that remnant sway characteristics were best predicted by models that included both sensory and motor noise, the graviceptive noise magnitude was about ten times larger than the proprioceptive noise, and noise sources with signal-dependent properties provided better explanations of remnant sway.Overall results indicate that humans dynamically weight sensory system contributions to stance control and tune their corrective responses to minimize the energetic effects of sensory noise and external stimuli.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomechanical Engineering, University of Twente, 7500 AE, Enschede, The Netherlands. H.vanderKooij@utwente.nl

ABSTRACT
We developed a theory of human stance control that predicted (1) how subjects re-weight their utilization of proprioceptive and graviceptive orientation information in experiments where eyes closed stance was perturbed by surface-tilt stimuli with different amplitudes, (2) the experimentally observed increase in body sway variability (i.e. the "remnant" body sway that could not be attributed to the stimulus) with increasing surface-tilt amplitude, (3) neural controller feedback gains that determine the amount of corrective torque generated in relation to sensory cues signaling body orientation, and (4) the magnitude and structure of spontaneous body sway. Responses to surface-tilt perturbations with different amplitudes were interpreted using a feedback control model to determine control parameters and changes in these parameters with stimulus amplitude. Different combinations of internal sensory and/or motor noise sources were added to the model to identify the properties of noise sources that were able to account for the experimental remnant sway characteristics. Various behavioral criteria were investigated to determine if optimization of these criteria could predict the identified model parameters and amplitude-dependent parameter changes. Robust findings were that remnant sway characteristics were best predicted by models that included both sensory and motor noise, the graviceptive noise magnitude was about ten times larger than the proprioceptive noise, and noise sources with signal-dependent properties provided better explanations of remnant sway. Overall results indicate that humans dynamically weight sensory system contributions to stance control and tune their corrective responses to minimize the energetic effects of sensory noise and external stimuli.

Show MeSH