Tanvi Bhatt - US grants

The long-term objective of this research is to develop an efficacious training paradigm to enhance stroke survivors' defense mechanisms against falls and possibly reduce healthcare cost. The Centers for Disease Control and Prevention estimates the direct medical cost for fall related injuries to be $34 billion annually. Forty percent to 70% of community-dwelling stroke survivors experience detrimental falls each year and tend to have 1.5 to 4 times higher risk of hip fracture than their healthy counterparts; with only less than 40% of those individuals regaining independent mobility. Falls, thus not only affect activities of daily living but also reduce mobility, increase risk of second stroke and mortality. Despite potential financial and functional implications of falls in this population, health-care personnel are limited in their ability to develop and validate interventions to reduce fall-risk for them. Further emphasis is placed on locomotor training with focus on enhancing paretic limb function. The project design consists of a randomized controlled trial to examine the ability of chronic stroke survivors to acquire, generalize and retain adaptations to slip-perturbation training for not only mitigating fall risk but also improving walking function. It also explores translation of this paradigm to the sub-acute population. The paradigm is novel in that it targets contributions of the paretic vs. non-paretic limbs on fall-risk through a bilateral training paradigm that involves training the non-paretic side first and then paretic to facilitate acquisition of fall-prevention skills on the paretic side, which may otherwise take longer to acquire training effects. The longer-term benefits of such perturbation training, targeting both limbs for reducing falls will be assessed not only in the laboratory but also in real life via wearable sensors, along with improved community walking function. The hypothesis of this study if supported by the results will provide an evidence-supported training protocol to reduce the fall-risk not only in people living with hemiparetic stroke but also among survivors of other acquired unilateral cortical lesions.

DESCRIPTION (provided by applicant): The long-term objective of this research is a prophylactic approach that can reduce the incidence of falls and the resulting injuries among older adults at risk and thus reduce its escalating medical cost. This project explores perturbation training through the use of treadmill device and a motor learning approach, in which experience with slip-like perturbation generated by that treadmill is used to prepare the motor system to develop and then put to use fall-resisting skills outside of training environment (cross-environment transfer). The computer-controlled treadmill is portable, safe and easy to operate, thus conducive for use in clinics or community centers. The study logically builds on and complements the team's previous and current research programs, and will further test that after such a single session, older adults at risk can retain such cross- environment transfer and reduce their likelihood of falls in everyday living for the next 6 to 12 months. Finally, the study will explore that such reduction of falls does not come merely from these persons' familiarity with the training or testing setup, protocol and environments.

? DESCRIPTION (provided by applicant): The long-term objective of this research is to develop an efficacious training paradigm to enhance older adults' defense mechanisms against falls and possibility reduce healthcare cost. The Centers for Disease Control and Prevention estimates the direct medical cost for fall related injuries to be $30 billion annually. Slips and trips combied account for more than 50% of the outdoor falls in community-dwelling older adults. These environmental perturbations are opposing in nature, with slips mainly resulting in backward falls and trips in forward falls. This project explores perturbation training through both slip and trip exposure based on the principles of motor learning. The project design consists of a randomized controlled trial to examine the ability of the central nervous system to mitigate the interference in stability control (if any) that is induced by opposing types of perturbations. It aso introduces a novel combined slip and trip perturbation training paradigm to enhance one's ability to retain and generalize the acquired fall-prevention skills to both types of falls. Slips and trip induced on an over ground walkway will be used to prepare the motor system to improve stability control and vertical limb support to resist falls. The longer-term benefits of such combined perturbation training over exclusive slip-only or trip-only perturbation training in reducing both laboratory-induced and real life falls will also be assessed. The hypothesis of this study if supported by the results will provide an evidence-supported training protocol to reduce the fall-risk among community-dwelling older adults.

Mild cognitive impairment (MCI) occurs along a continuum from normal cognition to dementia and affects nearly a quarter of individuals 70-79 years old, with the prevalence drastically increasing each decade after. Although most older adults with MCI (OAwMCI) are independent in their daily living, they are known to have significantly greater likelihood of falls compared to their cognitively intact counterparts. In addition to cognitive deficits, persons with MCI can experience motor dysfunction, including deficits in gait and balance. While changes in stance posture control and gait functionality have been thoroughly investigated in this population, reactive balance control and protective stepping responses that are recruited to recover from unpredictable, larger external perturbations have not yet been extensively examined. Additionally, though OAwMCI show slower adaptation and motor learning in comparison to their healthy counterparts, it remains to be unknown whether OAwMCI can adapt to task-specific training via repeated exposure to unpredicted perturbations as healthy older adults (OA) do. Furthermore, it is well established that OAwMCI have worse dual-task performance during both stance and gait. This presentation is related to impaired executive function, visuomotor function and spatial awareness. However, dual-task performance during perturbed stance and gait in association with increased fall-risk has not yet been investigated in OAwMCI. In addition, it is well-established that higher cortical centers play a vital role in modulation of reactive balance control. Interestingly, in OAwMCI, the decline in volitional balance control under sensory and cognitive challenges is corelated to an increased resting state activation of the default mode network, reduced white matter integrity and reduced gray matter volume. However, there is limited evidence examining the association between impaired structural integrity and neural correlates with reactive balance control measures and resulting higher occurrence of falls in this population. Our previous research has shown that two key variables, reactive control of stability and vertical limb support, contribute to more than 90% of laboratory slip-falls in OA. Thus, improving these key variables can contribute to significant reduction in fall risk in OA. However, such task-specific intervention-based studies are lacking in the MCI population. To fill the gap in the literature, our study proposes to investigate the differences in neuromechanics of reactive stepping responses to externally-induced balance perturbations in OAwMCI compared to OA. Further, our study proposes to relate reactive stability control to changes in brain structural and functional connectivity. Lastly, our study proposes to determine the effect of a novel task- specific perturbation-based cognitive-motor intervention for enhancing fall-resisting skills in OAwMCI.