Inclusion CriteriaAll subjects will be between the ages of 18-80, fluent English speakers, premorbidly right handed, and literate for stimulus sentences that are written at a minimum of a 4th grade reading level. In addition, all subjects will have a minimum high school or GED education, sufficient hearing acuity (aided or unaided) and auditory comprehension to follow task instructions, adequate visual acuity (aided or unaided) to read at least 14 pt. print on a computer screen, and adequate dexterity to press keyboard keys in response to stimuli.
Healthy subjects will have no history of mental, cognitive or other neurological deficits, adequate hearing and visual acuity (corrected or uncorrected) to follow task instructions and read at least 14 pt. print on a computer screen, and adequate dexterity to press keyboard keys to response stimuli. As with BD subjects, healthy subjects will be right handed, native English speakers, and literate for stimulus sentences. The Mini-Mental State Examination (Folstein et al., 1975) will be administered as a cognitive screen for healthy subjects, using a cut-off score of 27 (of total 30) for inclusion on the protocol.
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.
It should be emphasized that the BD subjects to be included on this protocol will have selective deficits (on the basis of neuropsychological test findings and screening to determine candidacy) and will be able to understand the purpose of our studies, the instructions for our tasks, and response demands. Patients who cannot understand the purpose of our studies, or the instructions or response demands of the tasks would not meet entry criteria. Only those subjects who pass the screening will be accepted on the protocol.