TRACK-HD is unique as it uses the most cutting-edge assessment techniques available to date, such as 3T MRI (3 tesla magnetic resonance imaging) and a range of computerized assessments that allow objective measurement of cognitive and motor functioning. In addition, the study is dynamic, in that it will incorporate promising new measures and refine its existing measures over time. These steps ensure that the final measures will be the most sensitive to subtle changes related to HD progression.