Methylphenidate Enhances Working Memory by Modulating Discrete Frontal and Parietal Lobe Regions in the Human Brain

The indirect catecholamine agonist methylphenidate (Ritalin) is the drug treatment of choice in attention deficit/hyperactivity disorder (AD/HD), one of the most common behavioral disor-ders of childhood (DSM-IV), although symptoms may persist into adulthood. Methylphenidate can enhance cognitive perfor-mance in adults and children diagnosed with AD/HD (Kempton et al., 1999; Riordan et al., 1999) and also in normal human volunteers on tasks sensitive to frontal lobe damage, including aspects of spatial working memory (SWM) performance (Elliott et al., 1997). The present study investigated changes in regional cerebral blood flow (rCBF) induced by methylphenidate during performance of a self-ordered SWM task to define the neuro-anatomical loci of the beneficial effect of the drug. The results show that the methylphenidate-induced improvements in work-ing memory performance occur with task-related reductions i