In order to do so, study subjects who fit inclusion criteria, including those with moderate to severe TBI who show persistent working memory weaknesses based on a screening, will be recruited. They will have three visits to UCLA. During the first visit, subjects will undergo an MRI protocol before and after taking a pill (drug or placebo, blinded). They will also participate in a number of paper and pencil cognitive tests. Then subjects will be enrolled in a 6 week computerized cognitive training program (CogMed). They will also be prescribed a drug/placebo pill (depending on which group they are randomized into), which they'll have to take at regular intervals during the 6 weeks. They will have weekly check in phone calls or visits by a coach trained in the program to make sure they are following the study protocol accurately, to have their questions answered, and for motivation. At the end of the training period, subjects will return to UCLA to again complete the MRI protocol and cognitive testing. After three months of enrollment, they will have a final visit to UCLA, including only cognitive testing. A total of 30 subjects will be entered into the study.