Experimental Brain Research

, Volume 143, Issue 4, pp 525–530 | Cite as

Directional control of reaching is preserved following mild/moderate stroke and stochastically constrained following severe stroke

  • David J. Reinkensmeyer
  • Alicia McKenna Cole
  • Leonard E. Kahn
  • Derek G. Kamper
Research Note

Abstract

Recent evidence suggests that brain injury can impair the ability to independently activate shoulder and elbow muscles. We hypothesized that if muscle activation patterns are constrained, then brain-injured subjects should not be able to accurately grade initial hand movement direction during reaching toward a broad range of target directions. To test this hypothesis, we measured hand trajectories during reaching in three-space by 16 hemiparetic stroke subjects to an array of 75 targets distributed throughout the workspace. Contrary to our hypothesis, we found that the ability to grade movement direction was largely preserved following mild and moderate stroke. However, the most severely impaired subjects exhibited a degradation of directional control consistent with a loss of independent muscle control. Initial and final hand movement directions for these subjects were grouped roughly in two opposing directions, in a plane parallel with the coronal plane of the body, rather than distributed across the normal range. Selection between the two movement directions appeared partially random, in that subjects initiated over 50% of movements in the direction generally opposite the intended target, for targets to one side of the body. These results suggest that individuals with severe stroke are constrained to use only two gross, stereotypical muscle coactivation patterns for reaching control, and that selection between these patterns is stochastically influenced as the actual direction of motion is not strictly predictable given the desired direction.

Keywords

Arm Reaching Motor control Stroke Movement synergy 

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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • David J. Reinkensmeyer
    • 1
    • 2
  • Alicia McKenna Cole
    • 3
  • Leonard E. Kahn
    • 3
    • 4
  • Derek G. Kamper
    • 2
    • 3
  1. 1.Department of Mechanical and Aerospace Engineering, Center for Biomedical EngineeringUniversity of California at IrvineIrvineUSA
  2. 2.Department of Physical Medicine and RehabilitationNorthwestern UniversityChicagoUSA
  3. 3.Sensory Motor Performance Program, Rehabilitation Institute of ChicagoChicagoUSA
  4. 4.Department of Biomedical EngineeringNorthwestern UniversityChicagoUSA

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