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AMONG PEOPLE WITH PARKINSON’S DISEASE Caitlin Ann Bryson, PT, PhD, DPT, SCS George Mason University, 2020 Dissertation Director: Dr. Clinton Wutzke Purpose: People with Parkinson’s disease (PD) demonstrate impairments within both the motor and cognitive domains. Within the motor domain, people with PD present with poor motor control strategies during unplanned turns. Turning, which requires a greater need for attentional resources than forward walking, makes up almost half of all steps taken during the day. Many of these turns are unplanned due to the need to avoid obstacles within an active environment. Unplanned turning, which results in decreased turn distance and increased turn duration among people with PD, can be made even more complex when attention must be shared between two tasks, such as when a person is walking and talking. The effects of cognitive loading on unplanned turning, however, has not yet been investigated. Additionally, within the cognitive domain, people with PD demonstrate poor cognitive flexibility, an important aspect of executive function which allows individuals to flexibly switch between tasks. Recent evidence suggests that cognitive flexibility is important to succeed in challenging walking conditions. However, cognitive flexibility has not yet been studied in relation to unplanned turning. The importance of studying motor control strategies and their relationship to cognitive flexibility among people with PD during complex environmental conditions is crucial for the rehabilitation field in order to further characterize the implications that complex environments have on people with PD. Thus, the purpose of this study was to determine the influence of cognitive demands on unplanned turning among people with PD. Two hypotheses were used: (1) Individuals with Parkinson’s disease will demonstrate decreased turn distance or increased turn time during unplanned turning with cognitive loading in comparison to unloaded walking trials; and (2) cognitive flexibility would be positively associated with turn distance and negatively associated with turn duration during dual-task trials. Methods: Twenty individuals with PD consented and completed the examination (age: 70.15±6.81; gender: 15M/5F). Participants completed a total of sixty trials of walking consisting of a randomized combination of both unplanned turns and forward walking. The sixty trials were broken into two blocks of thirty trials. Within each block, sixteen walking trials consisted of unplanned turns while the remaining fourteen consisted of forward walks. Participants were not informed of the order of unplanned trials. The second block additionally consisted of cognitive loading in which individuals performed a secondary task (serial subtraction by 3’s). Participants also completed the trail-making test (TMT). Within the TMT, TMT: part B (TMT-B) was used to assess cognitive flexibility. Results: Participants demonstrated decreased turn distance and increased turn time during dual-task trials compared to single-task (p=0.0016, p=0.0292, respectively). There was no association found between dual-task distance nor duration with TMT-B results among the majority of individuals. 3 individuals performed excessively slower on the test, suggesting poorer cognitive flexibility. This subgroup of individuals presented with a strong, nonsignificant, negative correlation between TMT-B and dual-task duration (r=-0.9752; p=0.1421), while a strong negative correlation was found to be significantly related to dual-task distance (r=-0.9993; p=0.0233). Conclusion: People with PD demonstrated different motor control strategies when completing unplanned turns while cognitively loaded. Differences in strategies may be employed to compensate for motor control and attentional impairments. Additionally, cognitive flexibility may only be associated with turn distance and turn duration among individuals with poorer flexibility. Further research is necessary to identify strategies and associations during complex walking conditions.