1. Ataxia Center, Massachusetts General Hospital and Harvard Medical School , Boston, MA 02114 , USA
2. Cognitive Behavioral Neurology Unit, Massachusetts General Hospital and Harvard Medical School , Boston, MA 02114 , USA
3. Laboratory for Neuroanatomy and Cerebellar Neurobiology, Department of Neurology, Massachusetts General Hospital and Harvard Medical School , Boston, MA 02114 , USA
4. Biostatistics Center, Massachusetts General Hospital and Harvard Medical School , Boston, MA 02114 , USA
5. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School , Boston, MA 02129 , USA