Reflex modulation is linked to the orientation of arm mechanics relative to the environment

Matthew A. Knitky, Vengateswaran J. Ravichandran, Randy D. Trumbower, Eric Perreault

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations

Abstract

To successfully complete a motor task, it is necessary to control not only the kinematics and dynamics of a limb, but also its mechanical properties. In a multijoint task such as the control of arm posture, limb mechanics are directional, resisting external disturbances more effectively in certain directions than others. It has been demonstrated that feedforward neuromotor pathways can regulate these directional characteristics of the arm to compensate for changes in the mechanical properties of the environment. However, it is unclear if spinal reflex pathways exhibit a similar specificity. The present results suggest that the sensitivity of the human stretch reflex also can be tuned to adapt the mechanical properties of the arm in a task appropriate manner. We hypothesized that the orientation of arm mechanics relative to the mechanical properties of the environment would influence reflex adaptation. Two destabilizing environments, oriented relative to the mechanical properties of the arm, were used to test this hypothesis. These environments were simulated using a 3 degrees of freedom (DOF) robot, which also was used to perturb arm posture. The resulting reflexes, assessed by electromyograms recorded from 8 muscles, were found to modulate in accordance with how the environmental instability was oriented relative to the mechanical properties of the arm. Our results suggest that stretch sensitive reflexes throughout the arm are modulated in a coordinated manner corresponding to the orientation of arm mechanics relative to the environment.

Original languageEnglish (US)
Title of host publicationProceedings of the 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'08
Pages5350-5353
Number of pages4
StatePublished - Dec 1 2008
Event30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'08 - Vancouver, BC, Canada
Duration: Aug 20 2008Aug 25 2008

Other

Other30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'08
CountryCanada
CityVancouver, BC
Period8/20/088/25/08

Keywords

  • Adaptation
  • Endpoint stiffness
  • Stretch reflex

ASJC Scopus subject areas

  • Computer Vision and Pattern Recognition
  • Signal Processing
  • Biomedical Engineering
  • Health Informatics

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    Knitky, M. A., Ravichandran, V. J., Trumbower, R. D., & Perreault, E. (2008). Reflex modulation is linked to the orientation of arm mechanics relative to the environment. In Proceedings of the 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'08 (pp. 5350-5353). [4650423]