1. McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
2. Ataxia Unit, Cognitive Behavioral Neurology Unit, Laboratory for Neuroanatomy and Cerebellar Neurobiology, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
3. University of Nebraska, Lincoln, Center for Brain, Biology, and Behavior, Department of Psychology, Lincoln, NE 68588, USA
4. Boston Children's Hospital, Division of Developmental Medicine, Boston, MA 02115, USA
5. Department of Psychology, Northeastern University, Boston, MA 02115, USA