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Estimation of Contact Regions Between Hands and Objects During Human Multi-Digit Grasping
Published on: April 21, 2023
An involuntary stereotypical grasp tendency pervades voluntary dynamic multifinger manipulation
Kornelius Rácz1, Daniel Brown, Francisco J Valero-Cuevas
1Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA.
Journal of Neurophysiology
|September 8, 2012
Summary
Neural control of multifinger manipulation faces challenges. Healthy hand control requires inhibiting synchronous grasp tendencies, which may have evolutionary roots.
Area of Science:
- Neuroscience
- Biomechanics
- Human motor control
Background:
- Multifinger manipulation requires complex coordination of individual finger movements and forces.
- Existing research often simplifies grasp tasks, potentially overlooking challenges in dynamic, individuated control.
Purpose of the Study:
- To investigate multifinger force variability during dynamic manipulation requiring individuated fingertip control.
- To identify the neural and mechanical factors influencing synchronous and individuated forces in grasp tasks.
Main Methods:
- Utilized a novel apparatus with three hinged finger pads for dynamic manipulation tasks.
- Subjects performed tasks involving maintaining grasp force against gravity while individually oscillating a finger pad.
- Employed mechanical analysis and simulations to interpret force variability data.
Main Results:
- Fingertip forces showed unexpected synchrony during dynamic manipulation, even when individuated control was required.
- This synchronous variability was unnecessary for the task and not explained by signal-dependent noise alone.
- Synchronous variability was absent in static grasp tasks but present in dynamic tasks demanding individuated control.
Conclusions:
- Dynamic multifinger manipulation necessitates continuous neural inhibition of inherent synchronous grasp tendencies.
- The human motor system has limited neuromechanical resources for complex, individuated grasp tasks.
- This finding may explain muscle coupling in early development and after brain injury, suggesting a potential evolutionary basis for these control mechanisms.
