1. To perform a 5-year study in which three consecutive days of DAR-0100A at a dose of 15 mg or placebo are administered intravenously over 30 minutes to 60 patients with SPD (12/yr) in a between-groups, randomized, double-blind design. Cognitive testing will be performed at baseline (Visit 1) and on the third day of drug/placebo administration (Visit 4). Subjects will return a minimum of two weeks later for Visit 5 to receive drug (if randomized initially to placebo) or placebo (if randomized to drug) in a double blind fashion in an identical protocol. This allows all patients to receive drug for Secondary Aim 1 while maintaining the blind. Baseline (Visit 1) and repeat cognitive testing (Visit 4) is also administered to 60 healthy controls per year (12/yr). The cognitive tests of working memory serving as primary outcome measures will include the modified AX-CPT (accuracy scores for AX, AY and BX and ANOVA), the N-back (delta difference 0-back-2-back), and the Paced Auditory Serial Addition Task (PASAT) (% correct and ANOVA). Other tests included are tests of working and verbal memory, executive function, and verbal learning for secondary outcome measures as well as comparison tests not hypothesized to change with drug.