Role of the Right Brain in Recovery of Language Function in Chronic Stroke

This study will examine in healthy individuals and in patients with aphasia (a language disturbance that is usually caused by stroke, brain disease, or injury) which parts of the brain are involved in naming everyday objects. In most people, language and speech originate in the left side of the brain. When this side of the brain is damaged, language function is often impaired. Often, however, function partly recovers, possibly because the right half of the brain takes over some language functions when the left half is injured. Healthy volunteers and patients with aphasia due to stroke may be eligible for this study. All candidates must be 18 years of age and older. Patients' aphasia must have occurred as the result of a stroke that occurred more than 12 months before entering the study. In addition, their stroke must not have affected the brainstem or cerebellum. Candidates will be screened with a medical history, brief physical examination, and questionnaire about handedness. Participants will undergo the following tests and procedures: Session 1: Magnetic resonance scanning (MRI) MRI is a diagnostic and research tool that uses a strong magnetic field and radio waves to obtain images of body organs and tissues, including the brain. The subject lies in a cylindrical machine for up to 60 minutes. Loud thumping noises occur when the radiofrequency circuits are switched; this noise can be muffled by the use of earplugs. Sessions 2 and 3: Picture naming during transcranial magnetic stimulation (TMS) For transcranial magnetic stimulation, a wire coil is held on the subject's scalp. A brief electrical current is passed through the coil, creating a magnetic pulse that stimulates the brain. The subject hears a click and feels a pulling sensation on the skin under the coil. There may also be a twitch in the muscles of the arm or leg. During the TMS, subjects are asked to name pictures of common everyday objects that appear on a computer screen. They are asked to name th