Pathways Mediating Impaired Postural Control in Parkinson's Disease

The purpose of this project is to use transcranial magnetic stimulation (TMS) to explore the state of excitability of corticocortical and corticofugal (cortex to spinal cord, cortex to brainstem to spinal cord) pathways that project to muscles that control the legs and trunk in people with Parkinson's disease. The outcome variables will be further analyzed to understand their relationship to quantitative measures of postural instability and gait dysfunction. As such, the project can be classified as basic physiologic research. The protocol is not designed to determine if measures of corticocortical or corticofugal excitability can be used as a biomarker to predict disease progression.