The purpose of this study is to determine if fMRI is precise enough to be used in preoperative decision making for patients who have brain tumors. Before a patient has brain surgery to have the tumor removed, functional mapping of the brain takes place either intra-operatively or post operatively after a subdural grid implant has been placed. Mapping helps the surgeon determine which areas of the brain are responsible for different important body functions. During this mapping procedure the surgeon determines if they can safely remove all or part of a brain tumor. The investigators are hoping to show that fMRI is just as accurate in mapping out different areas of the brain, without having to utilize an invasive form of brain mapping.