Identifying potential cortical mechanisms responsible for gait impairment in older adult fallers

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Project Summary Insufficient knowledge about the cortical mechanisms of gait impairment and fall risk in older adults limits the development of effective fall prevention interventions. In order to improve the current gait assessments and interventions in older adults, a more complete quantification of gait performance is required. Current quantification of cortical activity during gait is mostly limited to the prefrontal cortex (PFC) and young adults. The lack of information about the posterior parietal cortex (PPC; visual processing of orientation and motion of the body in space) activity during gait further limits the interpretability of the current fall literature. Older adults' visual processing is slower compared to young adults, therefore, establishing the PPC's role in gait for older adult fallers and non-fallers is critical for understanding the role of the PPC in fall risk. The proposed study's significant contributions include defining cortical activity during a visually complex gait task in older adults and establish how cortical activity affects the relationship between gait and fall predictors in older adult fallers and non-fallers. This contribution is significant because it will identify the unknown roles of the PPC and PFC during visually complex gait performance in older adult fallers and non-fallers, which will guide more effective fall prevention interventions. This proposed study is innovative because it quantifies PPC activity during a visually complex gait task that requires constant visual processing, mimicking gait demands in the home and community environments. The primary purpose of this proposal is to compare cortical activity in the PPC and PFC and key gait metrics in young, healthy older and older adult fallers during increasingly complex gait tasks and elucidate the effect PPC and PFC activity have on the relationship between gait and fall predictors in older adult fallers and non-fallers. This proposal addresses the following specific aims: Aim 1: Effects of age and fall status on PPC and PFC activity during gait Hypothesis 1: Older adults will have increased oxy- and decreased deoxygenated hemoglobin concentrations in the PPC and PFC during gait and gait variability, and reduced dynamic stability and step adjustment accuracy than young adults. Older adult fallers will exhibit the most cortical activity and gait variability, and least dynamic stability and step adjustment accuracy. PPC activity from over ground to stepping-stone treadmill gait will be greatest for the older adult fallers, as they will be unable to swiftly process the added visual stimuli. Aim 2: Mediation of the gait performance and fall predictor relationship by cortical activity Hypothesis 2: The relationship between gait performance and falls has been examined, however, how cortical activity mediates this relationship is unknown. Cortical activity, especially PPC activity, will be a significant mediator to the relationship between gait performance (dynamic stability, variability, and step adjustment accuracy) and fall predictors (fall history and fear of falling) in older adults. This will be the first rigorous analyses of gait performance, PPC and PFC activity, and fall predictors in older adult fallers and non-fallers.