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Processes underlying unintentional finger-force changes in the absence of visual feedback
Satyajit Ambike1, Vladimir M Zatsiorsky, Mark L Latash
1Department of Kinesiology, The Pennsylvania State University, 39 Rec. Hall, University Park, PA, 16802, USA, ssa17@psu.edu.
Experimental Brain Research
|November 24, 2014
Summary
In the absence of visual feedback, finger forces decrease over time, proportional to initial force, except for low forces where they increase. This suggests interacting central nervous system processes influence force control.
Area of Science:
- Neuroscience
- Biomechanics
- Motor Control
Background:
- Previous research indicates finger force declines exponentially without visual feedback.
- Understanding force regulation mechanisms is crucial for motor control studies.
Purpose of the Study:
- To investigate force production by index fingers of both hands without visual feedback.
- To analyze the temporal dynamics and inter-finger coordination during force maintenance.
Main Methods:
- Subjects exerted specified total forces with controlled contributions from each index finger.
- Force sensors measured finger forces without visual feedback.
- Analysis focused on force-time evolution, inter-finger force distribution, and time constants.
Main Results:
- Finger forces decreased exponentially with time, proportional to initial force magnitude, except for low initial forces (<7% MVC) which increased.
- Total force evolution mirrored individual finger force changes.
- Finger forces adjusted to promote more equitable force distribution between the two hands.
- Force-time dynamics followed exponential functions with a consistent time constant of approximately 15 seconds.
Conclusions:
- Two interacting processes, referent coordinate (RC) back-coupling and sensory adaptation, likely explain the observed force regulation patterns.
- RC back-coupling, involving CNS referent coordinate drift, accounts for force drops.
- Sensory adaptation may explain force increases at low initial forces.
- These mechanisms offer a unified explanation for force changes under varying conditions.
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