Increases in intrasynaptic (extracellular) dopamine concentrations associated with medications are routinely measured by changes in C-11 raclopride binding in PET scans. C-11 raclopride binds to postsynaptic D-2 receptors. If the intrasynaptic concentration of dopamine increases, it competes with raclopride leading to a weaker signal (i.e. decreased raclopride binding to D-2 receptors). After administration of a stimulant, associated increases in intrasynaptic dopamine compete with C-11 raclopride binding in this manner (Volkow, Wang et al. 2002). By using this technology we can document the change in D-2 binding in the intrasynaptic space achieved by armodafinil, and compare it to that achieved by a typical stimulant.