Title: “Planning and execution of skilled lower limb movements: advancing rehabilitation for community ambulation after incomplete spinal cord injury”
Supervisory Committee: Dr. Tania Lam (Research Supervisor), Dr. Daniel S. Marigold, Dr. Miriam Spering
University Examiners: Dr. Michael Hunt, Dr. Romeo Chua
External Examiner: Dr. Bradford J. McFadyen (Université Laval)
Chair: Dr. Thomas Oxland
Abstract: Individuals with partial paralysis due to motor-incomplete spinal cord injury (SCI) have difficulties traversing community environments despite intensive gait rehabilitation. Community ambulation requires adapting our gait to obstacles in the walking path that rely on movement planning and execution. Planning of such skilled movements begins by visually attending (overtly or covertly) to task-relevant locations, followed by integration of this visual input with somatosensory feedback (mainly proprioceptive) for executing coordinated limb movements. Because individuals with SCI may experience varying levels of proprioceptive impairment, the subsequent effects on movement planning and execution could impact the recovery of community ambulation. In this thesis, I developed novel approaches to investigate the planning and execution of lower limb movement. The first study established a novel protocol to test the deployment of covert (peripheral) visual attention for preparing foot placement during obstacle crossing planning in able-bodied controls. We quantified covert visual attention using an orientation discrimination task. We found that visual performance and sensitivity only decreased at the first of two stepping locations during obstacle-crossing planning compared to standing still. This result indicates that the brain uses peripheral vision to plan one step at a time. The second study determined if the execution of skilled walking after locomotor training in individuals with motor-incomplete SCI is related to adaptations in inter-joint coordination, quantified by joint angle-angle plots. We found that modifications in hip-ankle coordination and knee range of motion are related to improved skilled walking. In the third study, we tested the impact of proprioceptive deficits after motor-incomplete SCI on lower limb intersegmental dynamics. To test this, we manipulated inter-joint coordination by having participants perform lower limb pointing to different targets either with full and obstructed limb visual feedback. The results show that poorer proprioceptive sense in individuals with SCI is related to impaired control of intersegmental dynamics, especially around the knee. Collectively, my thesis provides novel insights into the planning and execution of skilled lower limb movements that can guide future rehabilitation interventions for the recovery of walking after SCI.