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Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
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On the effects of signal processing on sample entropy for postural control
Anat V Lubetzky1, Daphna Harel2, Eyal Lubetzky3
1Department of Physical Therapy, Steinhardt School of Culture Education and Human Development, New York University, New York, NY, United States of America.
Plos One
|March 2, 2018
Summary
Signal processing methods significantly impact sample entropy results in postural control research. Standardizing these procedures is crucial for consistent and comparable outcomes in studies of vestibular dysfunction.
Area of Science:
- Biomechanics
- Neuroscience
- Signal Processing
Background:
- Sample entropy is a popular measure for time series regularity in postural control.
- Inconsistent signal processing methods are used before calculating sample entropy in postural sway research.
- This variability hinders cross-study comparisons and interpretation of results.
Purpose of the Study:
- To investigate the impact of parameter choices and signal processing techniques on sample entropy outcomes in postural control.
- To compare sample entropy in individuals with vestibular dysfunction versus age-matched controls.
- To inform consistent methodologies for sample entropy application in virtual reality-based postural assessments.
Main Methods:
- Compared center-of-pressure (COP) sample entropy between vestibular dysfunction patients and controls.
- Participants stood on firm or compliant surfaces within a virtual reality environment.
- Analyzed effects of modifying radius of similarity (r), embedding dimension (m), down-sampling, filtering, differencing, and detrending.
Main Results:
- A significant main effect of surface was found for medio-lateral and anterior-posterior sway.
- A significant group × surface interaction in the medio-lateral direction was observed.
- Down-sampling and detrending maintained effects, while filtering and differencing altered sample entropy values.
Conclusions:
- Signal processing choices, such as filtering and detrending, significantly affect sample entropy calculations in postural control.
- Standardization of signal handling procedures prior to sample entropy computation is necessary for reliable comparisons across studies.
- Justification for chosen signal processing methods is essential when reporting sample entropy in postural control research.
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