Motor learning of protective responses to balance perturbations in persons with Parkinson's Disease

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Project Summary Two-thirds of persons with Parkinson’s disease (PwPD) fall yearly, resulting in non-fatal and fatal injuries. Many of these patients are recurrent fallers, due primarily to parkinsonian symptoms that interfere with postural control and limit postural responses to both self-initiated and external perturbations. These symptoms cause excessive co-contraction of agonists and antagonist muscle groups, hypometria, delayed stepping, and postural set inflexibility (i.e., an inability to quickly change responses to different types, conditions, and intensities of postural disturbances). Even with pharmacological and rehabilitation interventions, postural and balance deficits persist, and the risk of falls remains intractable. Among older adults, balance perturbation training is emerging as an effective method to reduce fall related injuries. In PwPD, however, one of the challenges to balance training is that postural inflexibility may negatively impact motor skill acquisition, retention, and generalization. As a result, motor learning strategies that are effective in individuals without PD may not be effective in PwPD. The overall objective of this PhD dissertation proposal is to determine the effect of practice schedule on the acquisition, retention, and generalization of protective balance responses in PwPD. The central hypothesis is that PwPD will acquire and retain protective balance responses to treadmill perturbations through blocked, but not random, initial practice schedules, and will require a follow-up set of random practice to generalize improvements to overground perturbations. In specific aim 1, I will compare improvements in protective stepping stability after a single session of blocked versus random practice of 10 slips and 10 trips in PwPD and age-matched healthy controls. In specific aim 2, I will compare generalization of protective stepping stability to unpracticed overground slip perturbations after blocked, followed by random practice sessions (blocked-random) to random, followed by blocked (random-blocked) practice sessions of treadmill-induced perturbations (10 slips and 10 trips) in PwPD and controls. Together, these findings will provide a basis for developing balance rehabilitation protocols based on motor learning principles to mitigate falls in PwPD compared to age-matched controls.