Lateralization of Central and Peripheral Influences on Bimanual Coordination
Open Access
- Author:
- Schaffer, Jacob Eric
- Graduate Program:
- Kinesiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 18, 2020
- Committee Members:
- Robert L Sainburg, Dissertation Advisor/Co-Advisor
Robert L Sainburg, Committee Chair/Co-Chair
Mark Latash, Committee Member
Jonathan Bates Dingwell, Committee Member
Meghan Vidt, Outside Member
Jonathan Bates Dingwell, Program Head/Chair - Keywords:
- Motor Control
Handedness
Brain Lateralization
Bimanual Coordination - Abstract:
- Bimanual movements, requiring fine coordination between the hands, make up a large portion of the tasks we perform every day. Neurophysiological evidence suggests that such bimanual movements recruit specialized neural circuits that do not appear to be a simple summation of dominant and non-dominant unimanual control networks. In addition, substantial asymmetries in coordination between the dominant and non-dominant limbs are well-known, and are thought to reflect lateralized cortical mechanisms of control between the hemispheres. This dissertation examines how a lateralized brain coordinates movements of both hands together, and what mechanisms allow for the fine coordination between the limbs necessary for functional bimanual movements. We first assessed whether bilateral feedback mechanisms involved in bimanual movements were asymmetric. We found that bilateral responses to perturbations during bimanual movements were expressed asymmetrically, such that non-dominant arm responses to perturbations to the dominant arm were stronger than dominant arm responses to non-dominant arm perturbations. We then studied two separate clinical populations to assess how central and peripheral mechanisms contribute to bimanual coordination. We found that stroke-related damage to one hemisphere affected certain aspects of bimanual control, specifically that predictive mechanisms that govern bilateral coordination are dependent on the left hemisphere (in right-handers). These findings indicate that assessment and training in cooperative bimanual tasks should be considered as part of an intervention framework for post-stroke physical rehabilitation. We also studied the effect of proprioception in bimanual coordination by studying movements of an individual who lacked somatosensory feedback due large fiber sensory neuropathy (LFSN). The results indicated that loss of proprioception had differential effects on each aspect of control in the two limbs. The non-dominant left hand of the deafferented participant showed substantial deficits in trajectory coordination, but was better able to stabilize position at the end of motion, whereas the dominant right hand showed better trajectory control, but demonstrated greater drift at the end of movement. These asymmetries were not apparent in the movements of age-matched control participants, suggesting that somatosensory signals from the two moving arms might be critical for synchronized bimanual movements. Lastly, we examined mechanisms by which activity from one hemisphere can influence the other. To do this, we tested how components of reflexes are altered by muscle activity on the contralateral side. Isometric force generation in one hand facilitated long-latency but not short-latency reflexes in the opposite wrist, suggesting that a facilitatory mechanism involving transcortical pathways may mediate interhemispheric interactions. Taken together, these studies show evidence of lateralization of bimanual control mechanisms and provides methodological considerations that may inform research on identifying and treating bimanual deficits in clinical populations.