The purpose of this protocol is to investigate plastic changes in human cerebral cortex in health and disease. The overall hypothesis is that it is possible to identify neuroimaging patterns reflecting reorganization in the human cerebral cortex using fMRI and that it is possible to obtain information on the mechanisms underlying some of these plastic changes by using magnetic resonance spectroscopy (MRS) of GABA. This information is potentially important for the understanding of mechanisms of cortical reorganization operating in humans. Patients and normal volunteers will be scanned at rest and during performance of different tasks. These studies should provide new information on mechanisms of human plasticity. The MRI techniques used for that purpose are functional MRI (fMRI), MR spectroscopy (MRS), and conventional MRI with magnets between 1.5 and 4 tesla.