<qa>  What is the effect of modafinil on cognitive function and brain physiology?In the present investigation our goal is to examine, in normal controls and patients with schizophrenia, the effect of modafinil, a drug that increases DA output in the frontal cortex, on cognitive function and brain physiology. We predict that both normal controls and patients with schizophrenia with the valval genotype will have a significant improvement in working memory compared with individuals possessing other genotypes. Furthermore, in conjunction with other NIMH imaging protocols, we predict that modafinil will produce a similar genotype-dependent effect on the neurophysiological correlates related to working memory assayed with fMRI. The present protocol will provide new insights on the importance of this genetic polymorphism in the regulation of aminergic-controlled cognitive function in normal individuals. Furthermore, this protocol will test whether modafinil offers a new treatment -based on genotype - for cognitive impairment in schizophrenia. The FDA granted a waiver for the use of Modafinil in this study. 