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Novel Behavioral and Neural Evidences for Age-Related changes in Force complexity
Yi-Ching Chen1,2, Linda L Lin3, Ing-Shiou Hwang4,5
1Department of Physical Therapy, College of Medical Science and Technology, Chung Shan Medical University, Taichung City, Taiwan.
Summary
Aging affects motor control complexity differently across time scales. Older adults showed more complex force tracking at short scales but less complexity at longer scales, impacting motor unit function.
Area of Science:
- Neuroscience
- Motor Control
- Aging Research
Background:
- The loss of complexity hypothesis suggests reduced physiological complexity with aging.
- Polyrhythmic movements may present an exception to this hypothesis.
- Understanding age-related changes in motor control is crucial for maintaining function.
Purpose of the Study:
- To investigate age-related changes in behavioral and neural complexity during polyrhythmic force tracking.
- To examine the multiscale entropy (MSE) of force output and motor unit (MU) activity in young and older adults.
- To determine if polyrhythmic movement complexity deviates from the general loss of complexity with aging.
Main Methods:
- Participants: Young (mean age 24.2 years) and older (mean age 68.1 years) adults.
- Task: Low-level force tracking using isometric index abduction to a compound sinusoidal target.
- Analysis: Multiscale entropy (MSE) of tracking force and inter-spike interval (ISI) of motor units (MUs) in the first dorsal interosseus muscle.
Main Results:
- Older adults exhibited greater MSE of tracking force at shorter time scales (more complex) but less complexity at longer time scales.
- MSE of force fluctuations (stochastic component) was generally lower (less complex) in older adults.
- Older adults showed greater mean and coefficient of ISI, with a tendency towards lower MSE of cumulative discharge rate (less complex MU activity).
Conclusions:
- Age-related complexity changes in polyrhythmic force-tracking are time-scale dependent.
- Behavioral consequences may stem from multifactorial origins, including impaired rate coding and altered motor unit discharge complexity.
- Polyrhythmic movements reveal nuanced age-related alterations in motor control complexity.
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