This NIH-funded study is a collaborative effort among a number of investigators across Pitt and the University of Michigan. The Co-Principal Investigators for this project are Dr. Caterina Rosano and Dr. Nicolaas Bohnen. The goal is to determine the causes of resilience in some of the elderly population to walking disturbances that are linked to changes in both cerebral small vessel disease and peripheral systems. It examines the nigrostriatal dopamine (DA) system as a potential source of resilience shown in a portion of the elderly population. The main hypothesis is that resilience may be due to a superior connectivity of sensorimotor networks driven by a higher nigrostriatal DA neurotransmission resulting in increasing the automaticity of walking and reducing prefrontal engagement while walking. The HMBL focus is testing mobility and balance function in subjects.