BACKGROUND: The coordination of steady state walking is relatively automatic in healthy humans, such that active attention to the details of task execution and performance (controlled processing) is low. Somatosensation is a crucial input to the spinal and brainstem circuits that facilitate this automaticity. Impaired somatosensation in older adults may reduce automaticity and increase controlled processing, thereby contributing to deficits in walking function. The primary objective of this study was to determine if enhancing somatosensory feedback can reduce controlled processing during walking, as assessed by prefrontal cortical activation.
METHODS: Fourteen older adults (age 77.1±5.56 years) with mild mobility deficits and mild somatosensory deficits participated in this study. Functional near-infrared spectroscopy was used to quantify metabolic activity (tissue oxygenation index, TOI) in the prefrontal cortex. Prefrontal activity and gait spatiotemporal data were measured during treadmill walking and overground walking while participants wore normal shoes and under two conditions of enhanced somatosensation: wearing textured insoles and no shoes.
RESULTS: Relative to walking with normal shoes, textured insoles yielded a bilateral reduction of prefrontal cortical activity for treadmill walking (ΔTOI = -0.85 and -1.19 for left and right hemispheres, respectively) and for overground walking (ΔTOI = -0.51 and -0.66 for left and right hemispheres, respectively). Relative to walking with normal shoes, no shoes yielded lower prefrontal cortical activity for treadmill walking (ΔTOI = -0.69 and -1.13 for left and right hemispheres, respectively), but not overground walking.
CONCLUSIONS: Enhanced somatosensation reduces prefrontal activity during walking in older adults. This suggests a less intensive utilization of controlled processing during walking.
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