Purpose of the study: AIM 1: Prospectively collect pre-operative \[functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), magnetoencephalography (MEG)\] and intra-operative mapping data in patients with intra-axial brain tumors to assess how well each modality predicts the location of eloquent brain function. In addition, each modality will be compared with the other. AIM 2: Assess reorganization of eloquent brain function and plasticity in patients with intra-axial brain tumors. This will be accomplished by prospectively collecting post-operative mapping studies and neuropsychological tests to compare them to prior mapping studies as stated above.