Parkinson’s disease (PD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and essential tremor (ET) affect over 10 million people in the United States. These debilitating movement disorders can be very difficult to distinguish from each other, have different prognoses, and can respond very differently (if at all) to available therapies. The purpose of this grant is to identify structural and functional changes in the brain using non-invasive neuroimaging techniques to develop sensitive and specific markers for each of these diseases, and then to track how these markers change as each disease progresses.