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Keeping still doesn't "make sense": examining a role for movement variability by stabilizing the arm during a
Chantelle D Murnaghan1, Mark G Carpenter2, Romeo Chua1
1School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
Journal of Neurophysiology
|December 9, 2016
Summary
Humans naturally make small movements, called oscillations, to sense their environment. This study found that even when an arm was stabilized, forces predicted greater movements, suggesting variability aids sensory information gathering.
Area of Science:
- Neuroscience
- Human Motor Control
- Sensory Perception
Background:
- Humans exhibit small-amplitude, high-frequency oscillations during postural tasks to maintain limb position.
- These involuntary movements may serve as an exploratory mechanism for acquiring sensory information.
- The role of movement variability in isolated upper limb postural tasks is not well understood.
Purpose of the Study:
- To investigate if movement variability, similar to whole-body postural control, occurs in an upper limb postural task.
- To determine if this variability aids in sensory information acquisition during a static limb position task.
- To examine the effect of limb stabilization on movement variability and predicted accelerations.
Main Methods:
- Participants maintained a static upper limb position in a supine position.
- A novel apparatus stabilized the limb without participant awareness ('locking' movements).
- Arm position was tested with and without visual feedback and with eyes open/closed.
Main Results:
- Forces recorded during limb stabilization predicted greater accelerations than observed during free movement.
- Angular accelerations increased when the limb was externally stabilized, particularly with eyes closed or visual feedback.
- Movement variability persisted even when the limb was externally stabilized, suggesting an intrinsic exploratory function.
Conclusions:
- Small limb displacements, or movement variability, may be an inherent mechanism for gathering sensory information.
- This variability appears to play a role in sensing the surrounding environment even during seemingly static tasks.
- The findings suggest that movement variability is not solely a response to sensory error but can actively contribute to sensory acquisition.
