The Trail Making Test in prodromal Huntington disease: contributions of disease progression to test performance. - O'Rourke JJ; Beglinger LJ; Smith MM; Mills J; Moser DJ; Rowe KC; Langbehn DR; Duff K; Stout JC; Harrington DL; Carlozzi N; Paulsen JS (Journal of clinical and experimental neuropsychology, 2011)