Posterior parietal cortex activity during visually cued gait: a preliminary study.

Safe gait requires visually cued (VC) step adjustments for negotiating targets and obstacles. Effective step adjustments rely on good visuospatial processing. The posterior parietal cortex (PPC) is implicated in visuospatial processing, yet empirical evidence is limited for the PPC's role during gait in humans. Increased cortical control of gait is associated with higher gait variability, a marker of gait performance and fall risk among older adults. However, the cortical underpinnings of gait variability in visually complex environments are not well established. The primary aim of this preliminary study was to assess PPC activity during VC gait and VC gait with perturbations (VCP). A secondary aim was to determine how PPC activity relates to gait variability during VC and VCP gait. Twenty-one healthy young adults completed three treadmill gait conditions at preferred speed: non-cued (NC) gait, VC gait, where stepping targets were presented in a regular pattern, and VCP gait, where stepping target positions were pseudorandomly shifted. Functional near-infrared spectroscopy quantified relative changes in deoxygenated and oxygenated hemoglobin (ΔHbO2) concentrations in the PPC. Inertial measurement units quantified gait variability. Moderate effects were observed for more positive ΔHbO2 from NC to both VC and VCP gait, likely reflecting the increased visuospatial processing demands. Stride time variability was positively correlated with PPC ΔHbO2 during VC gait, suggesting a potential role for the PPC in modulating temporal components of VC gait. Extending these findings to older adults will help to elucidate the PPC's role in gait adaptability and fall risk with aging.