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Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
Pointing with the wrist: a postural model for Donders' law
Domenico Campolo1, Ferdinan Widjaja, Mohammad Esmaeili
1School of Mechanical and Aerospace Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore. d.campolo@ntu.edu.sg
Experimental Brain Research
|June 7, 2011
Summary
The central nervous system uses consistent wrist and forearm joint angles for pointing. A new model explains these movements by balancing minimal rotation and comfortable postures, accurately predicting human pointing behavior.
Area of Science:
- Neuroscience
- Biomechanics
- Human Motor Control
Background:
- The central nervous system employs stereotypical joint angle combinations for 2D pointing.
- Donders' law describes the relationship between eye position and head orientation, and a similar principle is observed in wrist movements.
Purpose of the Study:
- To confirm and analyze Donders' law for wrist/forearm joint angles during pointing tasks.
- To develop a postural model explaining the observed joint angle distributions and characteristics.
- To investigate the role of extrinsic and intrinsic costs in controlling wrist orientation during pointing.
Main Methods:
- Experimental analysis of wrist configurations during human pointing tasks.
- Development of a four-parameter postural model incorporating wrist torsion.
- Simulation of pointing movements using a cost minimization framework (extrinsic and intrinsic costs).
- Fitting quadratic surfaces to experimental and simulated data to compare Donders' law representations.
Main Results:
- Experimental wrist configurations during pointing tasks are characterized by subject-specific Koenderink shape index and pronosupination bias.
- The developed postural model accurately explains these characteristics by defining a task-equivalent manifold (TEM) parameterized by wrist torsion.
- Simulations revealed that both extrinsic (minimal rotation) and intrinsic (postural comfort) costs are necessary to replicate experimental wrist/forearm data, unlike eye movements.
- Fitting Donders' law to simulated data resulted in similar errors as fitting to experimental data.
Conclusions:
- The study confirms and extends Donders' law to wrist/forearm pointing.
- A novel postural model effectively explains the redundancy and control of wrist movements during pointing.
- The findings highlight the importance of considering both movement efficiency and postural constraints in motor control.
- The model provides a framework for understanding the neural control of multi-joint movements.
