[1] Duke Univ, Dept Neurol, Durham, NC 27708 USA
[2] Univ Pittsburgh, Dept Behav & Community Hlth Sci, Pittsburgh, PA USA
[3] SSRS, Glen Mills, PA USA
[4] Michael J Fox Fdn Parkinsons Res, New York, NY USA
[5] Univ Penn, Dept Psychiat, Philadelphia, PA 19104 USA
[6] Univ Toronto, Toronto Western Hosp, Edmond J Safra Program Parkinsons Dis, Toronto, ON, Canada
[7] Univ Pittsburgh, Dept Neurol, Pittsburgh, PA 15260 USA