The Role of Central Nervous System in Complex Walking Among Older Adults

Gait is a complex process which requires dynamic interactions between musculoskeletal, cardiopulmonary, and nervous systems. Previous studies identified brain regions correlated with simple walking, suggesting importance of central nervous system (CNS) in maintaining walking performance. Most of the previous evidence focused on speed and length of gait, and finding of brain regions with gait characteristics from other important domains was limited. Compared to simple walking, community walking is accompanied with greater environment challenges, and likely involves additional neural inputs of the brain. Thus, studying usual walking speed may not reveal the whole picture of neural correlates of community walking in daily life. This dissertation aims to identify brain regions related to performance of different walking tasks to provide evidence of the role of brain in community walking in older adults. In the first and second paper, I included over 200 participants from the Health, Aging, and Body Composition study in which gray matter volume and gray matter density were measured using magnetic resonance imaging. In the third paper, I included 117 participants from three independent samples with prefrontal cortex (PFC) activation measured using functional near infrared spectroscopy. Frontal, anterior cingulate, superior parietal, cerebellar, and subregions from basal ganglia related to executive and motor function are associated with aspects of walking performance, including spacing and timing control. Middle and superior frontal gyrus, postcentral gyrus, and superior temporal gyrus, related to executive function, somatosensory, and vestibular function, respectively, are involved during fast paced walking but not simple walking. I observed increased PFC activation during dual-task walking compared to simple walking, and heterogeneous PFC activation patterns that differ in walking performance. Brain is important for spacing and timing control during walking, and is increasingly engaged as the challenges of community walking increase, shown by the results of structural and functional correlates of complex walking compared with simple walking. The public health significance of this work includes evidence for 1) identifying early subclinical brain impairment using walking performance; 2) interventions to improve the performance of community walking; and 3) goal-oriented exercise and training that restores efficiency in PFC control to improve community walking