Fig. 1: The order of study interventions and measures for the two arms of the study is shown.

The arms were conducted sequentially, with Arm 1 completed prior to Arm 2 commencing. The order of treatments within each arm (active drug or placebo first) was randomised and counter-balanced to ensure approximately equal numbers of subjects receiving drug or placebo first. Subjects and investigators were blind to the treatment allocation. The washout period was a minimum 10 days for amisulpride, and a minimum of 28 days for aripiprazole. Cognitive testing and assessment of parkinsonian symptoms using the Simpson Angus Scale (SAS) were performed at baseline, follow up (FU) 1 and FU 2 visits.