Mobility Function and Aperiodic Electrocortical Activity in Younger and Older Adults.

Mobility declines with age to the extent that walking speed is often considered a vital sign. Identifying electrocortical changes behind this decline would aid with early identification and intervention. Electroencephalography (EEG) metrics may provide insight into neural factors contributing to mobility decline with aging. Recent research has shown a differentiation in aperiodic EEG across age groups, cognitive abilities, and populations with neurological injury. Aperiodic EEG is defined as the broadband, or non-oscillatory, component of the EEG power spectrum described by an exponent and offset. However, it is unknown if aperiodic EEG differs between mobility tasks or brain regions. The purpose of this study was to 1) compare aperiodic EEG in healthy older and younger adults at rest and while walking and 2) determine if oscillatory and aperiodic EEG in sensorimotor brain regions are predictors of a slower walking speed, regardless of age and other demographic factors. We analyzed EEG collected while participants were sitting at rest and walking on a treadmill in 31 younger adults (age: $24~\pm ~4$ , mean ± s.d.) and 59 older adults (age: $74~\pm ~6$ ), with no known cognitive decline or neuromuscular impairment. We found that older adults had lower aperiodic exponent and offset at both rest and during walking, but only a subset of brain regions showed age group differences. Using machine learning methods, we found that right sensorimotor alpha power, left sensorimotor aperiodic offset, and left sensorimotor beta power had the largest effect on individualized walking speed, after the demographics of age, waist circumference, and sex. These results suggest age differences in aperiodic EEG are regionally specific, and that aperiodic and oscillatory EEG describe differences in individualized walking speed that demographics alone cannot.