Top-Down Attentional Control of Visual-Processing

* INCLUSION CRITERIA: All Subjects 1. All subjects will be 18 years of age or older and have at least a high school education. 2. Capacity to provide their own informed consent, understand and cooperate with study procedures. 3. Able to read and write in English to guarantee understanding of all written and spoken instructions, which are in English. Patients: 1. Unilateral or bilateral focal lesions of prefrontal, parietal, occipital or temporal cortex, or amygdala. 2. At least three months post-stroke, lobectomy and or neurosurgical resection. Healthy volunteers: 1\. Neurologically normal and in good general health. EXCLUSION CRITERIA Patients: 1. Any neurological or psychiatric disorder not related to the focal lesion (e.g., epilepsy, schizophrenia, etc.). Epilepsy patients who have undergone surgery and as a result are seizure free may be recruited. 2. Previous head injury. 3. Present or past (within past 6 months) drug or alcohol abuse or addiction as determined by a qualified study neurologist/psychiatrist. 4. Radiation treatment to the brain during a three-month period prior to the experiment. Healthy volunteers: 1. Any neurological or psychiatric disorder (e.g., epilepsy, schizophrenia, etc.) 2. Previous head injury. 3. Present or past (within past 6 months) drug or alcohol abuse or addiction based on DSM-5 criteria as determined during History and Physical exam. ADDITIONAL EXCLUSION CRITERIA FOR MRI SCAN: Patients and Healthy volunteers: 1. Women who are pregnant and women of child-bearing potential who refuse to undergo a urine pregnancy test will be excluded from fMRI experiments. 2. Subjects who have contraindications to MRI scanning will be excluded from fMRI experiments but included in cognitive experiments. These contraindications include: 1. central nervous system aneurysm clips; 2. implanted neural stimulator; 3. implanted cardiac pacemaker or defibrillator; 4. cochlear implant; 5. ocular foreign body (e.g., metal shavings); 6. insulin pump; 7. metal shrapnel or bullet; 8. any implanted device that is incompatible with MRI. 3. Conditions that preclude scanning, e.g., morbid obesity, claustrophobia. ADDITIONAL EXCLUSION CRITERIA FOR TASKS INVOLVING COLOR DISCRIMINATION: Patients and Healthy volunteers: Subjects who are determined during screening or history and physical exam to be color-blind will be excluded from participating in certain tasks that involve color discrimination.