Specific Aim 2A. To test whether aripiprazole is superior to risperidone in permitting modafinil enhancement of LC and PFC activity and cognition. Hypothesis 2A. The ARI group, vs. RIS group, will exhibit 2A) greater effects of Modafinil (vs. Placebo) on task-related LC activity and greater cognitive control task improvement. Specific Aim 2B. To test the role of α2 autoreceptor antagonism by antipsychotic medications as a source of blunted LC response to Modafinil. Hypothesis 2B. Across groups (ARI+RIS), α2 autoreceptor antagonist load correlates with impaired Modafinil effects (vs. Placebo) on task-related LC activity and cognitive control performance. These aims are related but not interdependent: antipsychotic effects on LC/PFC/cognitive function, vs. antipsychotic effects in moderating modafinil actions on these same measures, represent distinct research questions.