Objective: The primary aim of this preliminary study was to explore pre-frontal cortex (PFC) and posterior parietal cortex (PPC) activity in older adults (OAs) during visually perturbed gait (VPG). A secondary aim was to relate PFC and PPC activity during VPG to cognitive performance in OAs. We hypothesized that PFC and PPC activity will increase from regular gait to VPG in young adults (YAs), but to a greater extent in OAs, which will relate to poorer cognition.

Background: Cognition is critical to gait preservation in OAs, such that executive function and memory scores predict gait decline. Everyday gait requires corrective step adjustments, which demand cognitive resources to complete. OAs make less accurate step adjustments, translating to increased fall risk. OAs also have elevated PFC activity during unperturbed gait. Quantifying PFC and PPC (sensorimotor integration area) activity during VPG will help identify cortical mechanisms of gait impairment in OAs.

Method: Cortical activity was quantified in six YAs (22.0[4.1]yrs, 3F) and 11 OAs (68.6[3.5]yrs, 7F) using functional near-infrared spectroscopy, which quantifies relative concentration changes in deoxygenated and oxygenated hemoglobin (HbO2). The MoCA quantified global cognition. Two 3-minute treadmill gait conditions were completed at preferred speed: regular walking and VPG. VPG used projected stepping targets – attuned to participants’ foot size, step length, step width, and gait speed – on the treadmill belt. Perturbed targets randomly moved in the anterior-posterior or lateral direction at 130% of participants’ step length.

Results: Two-way mixed design ANOVAs showed no main effect of group, but significant group*condition interactions for both PFC (F_1,15=9.36, p=.008) and PPC (F_1,15=7.39, p=.016) HbO2 concentration changes. Post-hoc tests revealed PFC activity increased significantly from regular gait (-0.29[0.72]μmol) to VPG (+0.22[0.45]μmol) in YAs. In OAs, lower MoCA memory scores significantly related to greater PFC activity during VPG (ρ=0.63; p=0.039).

Conclusion: Preliminary findings suggest cortical activity increases in YAs from regular gait to VPG, but not in OAs. This could reflect visual processing speed differences between groups, or that OAs require more cortical activation for regular gait. The association between greater PFC activity during VPG and poorer memory in OAs could reflect a cognitive compensatory mechanism to maintain task performance during VPG.

References: Morris, R., Martini, D. N., Smulders, K., Kelly, V. E., Zabetian, C. P., Poston, K., Hiller, A., Chung, K. A., Yang, L., Hu, S.-C., Edwards, K. L., Cholerton, B., Grabowski, T. J., Montine, T. J., Quinn, J. F., & Horak, F. (2019). Cognitive associations with comprehensive gait and static balance measures in Parkinson’s disease. Parkinsonism &; Related Disorders, 69, 104–110. https://doi.org/10.1016/j.parkreldis.2019.06.014

Mazaheri, M., Hoogkamer, W., Potocanac, Z., Verschueren, S., Roerdink, M., Beek, P.J., Peper, C., Duysens, J. (2015). Effects of aging and dual tasking on step adjustments to perturbations in visually cued walking. Experimental brain research 233, 3467-3474

McCrum, C., Gerards, M.H., Karamanidis, K., Zijlstra, W., Meijer, K. (2017). A systematic review of gait perturbation paradigms for improving reactive stepping responses and falls risk among healthy older adults. European Review of Aging and Physical Activity, 14(1). doi:10.1186/s11556-017-0173-7

Stuart, S., Vitorio, R., Morris, R., Martini, D.N., Fino, P.C., Mancini, M. (2018). Cortical activity during walking and balance tasks in older adults and in peoplewith Parkinson’s Disease: A structured review. Maturitas, 113, 53-72 doi:10.1016/j.maturitas.2018.04.011

Ebaid, D., Crewther, S.G. (2019). Visual information processing in young and older adults. Frontiers in aging neuroscience, 11, 116

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cortical-activity-during-visually-perturbed-gait-in-older-adults/