Normal tissue response is critical for brain radiotherapy, especially for dose escalation which carries with it an increased incidence of radiation-induced brain injury. Although radiation toxicity and limiting dose for anatomically critical structures of the brain have been well studied and documented, little is known for functionally critical brain regions and treatment of cognitive sequelae of cranial radiotherapy is limited. The objective of this clinical protocol is to accumulate preliminary data for future studies aiming to quantify dose response for functionally critical brain regions for brain radiotherapy. We plan to achieve this objective by correlating the radiation-induced complications and radiological changes with the radiation dose to the selected functionally critical brain regions for 25 patients. Each participating patient will receive brain fMRI to identify brain regions for processing visual, working memory and language functions. The image co-registration algorithm developed previously by our group will be used to co-register these regions on the CT scans for radiotherapy treatment planning for radiation dose calculation. Radiation-induced changes in cognitive functions will be evaluated using the modified mini mental status exam (3MS) and fMRI during the routine follow-up. The knowledge derived from this study might significantly improve the quality of life and allow safer dose escalation for patients receiving brain radiotherapy.