Superior Predictive Control of Intersegmental Dynamics in Dominant Arm Coordination

Open Access
Embar, Tarika
Area of Honors:
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Robert L Sainburg, Thesis Supervisor
  • Mary Jane De Souza, Honors Advisor
  • handedness
  • Dynamic Dominance
  • Sainburg
Previous research has supported a hypothesis of motor lateralization that attributes specialization for predictive coordination of interjoint coordination to the dominant hemisphere/limb system. This has been supported by reaching studies in healthy young participants (Mutha et al., 2013; Schaffer and Sainburg, 2017), and in stroke survivors with unilateral hemisphere lesions (Schaefer et al., 2009). While the studies in healthy subjects have shown differences in coordination between the arms, the nature of the reaching tasks leave open the possibility that the differences in coordination between the arms might be influenced by the perceptual and cognitive demands of targeted reaching movements, such as visually specified spatial precision. The purpose of this experiment was to find interlimb differences in interjoint coordination for a simple task that does not require either visual feedback nor precise spatial goals. Subjects performed slow and fast alternating unilateral wrist ulnar/radial deviation task, in which the wrist was free to move while the forearm rested in the neutral position. The task was to move the wrist throughout the range of motion using continuous rhythmic and alternating ulnar/radial deviation motions, reflecting a ‘chopping’ motion of the hand. Participants were instructed to prevent motion in the uninstructed degrees of freedom, flexion/extension or pronation/supination. They were instructed to move “slow” and “as fast as possible”. Under the slow condition, all participants moved at a similar frequency (0.650 Hz) and were able to make fairly isolated radial-ulnar deviation motions. However, when participants moved “as fast as possible”, the range of radial-ulnar deviation decreased, and the motion in uninstructed degrees of freedom increased. The non-dominant arm incorporated substantially more pronation/supination than did the dominant arm. We conclude that interjoint coordination, measured as the ability to prevent motion in uninstructed degrees of freedom, is substantially better coordinated in the dominant arm than the non-dominant arm. These results support our hypothesis that the dominant hemisphere/arm system is specialized for interjoint coordination, and that this is reflected in simple tasks that do not require a visually specified target.