On the control of movement variability through the regulation of limb impedance

• Main Author: Lametti, Daniel R.
• Format: Others
• Language: en
• Published: McGill University 2007
• Subjects: Arm > Movements.; Human mechanics.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101860

Humans routinely make movements to targets that have different accuracy requirements in different directions. Examples extend from everyday occurrences such as grasping the handle of a coffee cup to the more refined instance of a surgeon positioning a scalpel. The attainment of accuracy in situations such as these might rest upon the nervous system's capacity to regulate the limb's resistance to displacement, or impedance. To test this idea, subjects made movements from random starting locations to targets that had shape dependant accuracy requirements. A robotic device was used to assess both limb impedance and patterns of movement variability just as the subject reached the target. Impedance was seen to increase in directions where required accuracy was high. Furthermore, independent of target shape patterns of limb stiffness were seen to predict spatial patterns of movement variability. The nervous system was thus seen to modulate limb impedance in wholly predictable environments to shape movement variability and achieve reaching accuracy.