Despite the prevalence of working memory deficits following traumatic brain injury (TBI), the scientific data regarding pharmacological treatment of this problem is limited. As deficits in working memory are known to have a significant impact on functional outcomes for individuals with TBI, further research in this area is essential in order for physicians to be able to treat this problem more effectively. The primary goal of the proposed project is to examine the efficacy of a particular pharmacological agent, CDP-Choline, in the treatment of working memory deficits following traumatic brain injury (TBI). The study sample will consist of 48 subjects: A group of 24 individuals who have sustained moderate to severe TBI, and a group of 24 healthy controls. Each group will be divided into a placebo and treatment group. The project will utilize functional Magnetic Resonance Imaging (fMRI) to investigate the cerebral neurophysiological effects of treatment with CDP-Choline. A working memory task (N-Back) will be employed during fMRI sessions. In addition, the effects of treatment with CDP-Choline on neuropsychological testing performance will also be evaluated, and the correlations between behavioral performance and neuroimaging results will be observed. We will achieve these goals by comparing baseline neuropsychological testing results as well as fMRI results, with a second set of testing and neuroimaging results obtained following 1 month of pharmacological treatment with CDP Choline or placebo. Based on our preliminary studies and the available literature, we expect to see the following: Baseline fMRI results are expected to show that individuals with TBI display altered patterns of cerebral activation during a working memory task, as compared to healthy controls. With CDP-Choline treatment, we expect TBI subjects to display fMRI laterality and dispersion patterns that more closely resemble patterns of healthy controls. In addition, we anticipate improvements in behavioral performance on both the specific working memory task (N-Back), and on traditional neuropsychological tests to be associated with CDP-Choline treatment, with greater magnitude of change on testing results for the TBI group as compared to any changes noted for the control or placebo groups. Finally, we anticipate that specific significant correlations will be observed between neuropsychological testing results and neuroimaging findings, and that the strength of these relationships will be greater for the TBI treatment group, as compared to the placebo or healthy control groups. By conducting the proposed study in this manner, we hope to provide scientific data that will allow for improved treatment, and ultimately improved functional outcomes for individuals who have sustained TBI.