Grasping Function after Spinal Cord Injury

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Grasping behaviors, which are essential for daily-life functions, are largely impaired in individuals with cervical spinal cord injury (SCI). Although rehabilitative interventions have shown success in improving the ability to grasp following injury their overall effects remain limited. The goals of this proposal are to examine the contribution of physiological pathways to the control of grasping behaviors after cervical SCI, and to maximize the recovery of grasping by using tailored non-invasive stimulation protocols with motor training. We propose to study two basic grasping behaviors: a precision grip and a power grip. These behaviors are crucial because they provide the basis for a number human prehensile manipulations and are also necessary skills for eating, writing, dressing, and many other functions. Thus, our results may have a direct impact on the quality of life for veterans and their caregivers by enhancing their independence and level of care. In Aim 1, we will investigate the contribution of corticospinal and brainstem pathways to the control of hand muscles involved in precision and power grip after cervical SCI. Transcranial magnetic stimulation (TMS) will be used to examine transmission in corticospinal and intracortical pathways targeting finger muscles and an acoustic startle stimulus with and without TMS will be used to examine the contribution from brainstem pathways. Functional magnetic resonance imaging (fMRI) will be used to further assess changes in brain activity during these hand motor tasks. In Aim 2, we propose to enhance the recovery of grasping by using novel tailored protocols of non-invasive repetitive TMS targeting late indirect (I) descending volleys (iTMS) and an acoustic startle stimuli. iTMS and startle will be used during precision and power grip movements in a task-dependent manner to induce cortical and subcortical plasticity and enhance voluntary output of hand muscles (Aim 2a). Later, iTMS and startle will be applied in a task-dependent manner during a motor training task that involves precision and power grip (Aim 2b). These unique approaches aim at promoting neuroplasticity during functionally relevant grasping movements has not been used before. The proposed experiments will provide new knowledge on mechanisms of grasping functions which will be used to guide functionally-relevant plasticity-inducing protocols to enhance recovery of hand function. The absence of well-accepted treatments for grasping motor impairments for veterans with cervical SCI and the limited behavioral gains of present interventions underline the importance of these investigations.