For prefrontal BD subjects, only adult patients with focal damage confined to the prefrontal lateral or orbitomedial areas of either or both hemispheres will be included in the study. Cortical damage will be determined on the bases of neurological and neuropsychological examinations and confirmed by MRI or CT studies. All patients with stroke and penetrating head injury will be tested at least 3 months post-onset of neurological damage to ensure a stable medical condition. All patients with resected brain tumor will have completed radiation therapy and regimen of steroid medication. Dates and course of radiation therapy will be documented.