Dose Response Analysis: Logistic regression analysis will be used to assess the likelihood of complications to functionally critical brain regions as a function of radiation dose. The dependent variable will be the binary indicator that identifies patients' manifesting complications (decline of 3MS examination score and N-Back test, radiological/functional changes identified on MRI and fMRI) attributed to radiation exposure. The logistic regression model will include relevant subject level factors (e.g., age, gender, baseline Karnofsky performance status, tumor location, recent seizures, anti-epleptic medications) as covariates. The fitted logistic normal tissue complication probability (NTCP) model will permit estimation of the probability of significant complications associated with any radiation dose to the area, allowing the limiting dose to be calculated as the dose expected to induce complication with an acceptable probability (e.g., 5%).