Neural correlates of whole-body motion perception during balance perturbations in stroke survivors and their relationship to balance function

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PROJECT SUMMARY/ABSTRACT Both sensory and motor processing are impaired post-stroke, but frequently studied in isolation, with most rehabilitation focused on the motor system. Our current understanding of the perception of body position and movement (i.e. proprioception) is limited due to existing methodologies that are subjective, lack precision, and are often assessed in single joints of the upper limb during non-functional behaviors. My dissertation research used robotic methods to understand proprioceptive contributions to motor learning at a perceptual and neurophysiological level. Learning was associated with enhanced proprioceptive function and changes in sensorimotor neurophysiology. While these findings supported the value of using objective measures to quantify proprioception in the context of learning and identified underlying neural substrates, the neural mechanisms mediating proprioceptive contributions to functional behaviors, such as balance, is unknown. When balance is perturbed, the brain must integrate sensory input across multiple joints and limbs to perceive body position and plan the appropriate muscle response. Findings from our lab demonstrate that stroke survivors have altered cortical responses and muscle activation patterns in response to a perturbation, but it is unknown whether these abnormal responses are related to impairments in whole-body motion perception. Objective biomarkers, including structural integrity and cortical responses to balance perturbations, of balance function are necessary to identify individuals at risk for falls and to inform the development of targeted interventions that capitalize on an individual’s underlying brain-balance profile. Towards this long-term goal, we will pursue the following aims in chronic stroke survivors (N=20) and neurotypical older adults (N=20): 1) test whether worse whole-body motion perception is associated with worse balance function; 2) determine if cortical responses evoked during balance perturbations are modulating according to the difficulty of discriminating between balance perturbations; and 3) test whether measures of structural integrity in sensory pathways and cortical response latency are associated with balance function. To our knowledge, this is the first study using a multi-modal approach to identify brain-balance relationships underlying somatosensory perception during functional behaviors. If successful, such findings may contribute to a shift in existing rehabilitation interventions focused on the motor system towards integrative approaches that address sensory and perceptual contributions to movement. Given increased risk of falls with aging that is further increased post-stroke, developing structural and functional biomarkers of somatosensory perception and balance function is necessary to identify individuals at risk for falls, and to advance development of effective, evidence-based rehabilitation interventions.