Parkinson's disease (PD) is a neurodegenerative disorder with major clinical sensorimotor signs, including bradykinesia (slowed movements), rigidity, tremor and postural instability with gait disability. It affects multiple aspects (domains) of balance and gait, namely, anticipatory postural adjustments prior to voluntary movements, automatic postural responses to external perturbations, postural sway in stance and dynamic stability during gait. The goal of the present work is to improve our understanding of brain networks involved in balance and gait disorders by studying the associations between structural/functional characteristics of the brain with motor behaviors in people with PD and older adults.