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Discover 23,284 clinical trials near Maryland. Find research studies in your area.
Showing 16941-16960 of 23,284 trials
NCT01246128
Background: \- Previous studies have suggested that smoking cigarettes affects the number of receptors in the brain for nicotine, a chemical present in cigarette smoke. The receptors play a role in an individual's ability to think and concentrate. Many people with schizophrenia and similar disorders smoke, and research suggests that smoking may temporarily improve concentration and focus in individuals with schizophrenia. Researchers are interested in studying both current smokers and nonsmokers with schizophrenia to determine whether smoking affects the number of nicotine receptors in the brains of people with schizophrenia. Objectives: \- To study the distribution and volume of nicotine receptors in the brains of individuals with schizophrenia who are either nonsmokers or current smokers. Eligibility: * Individuals between 18 and 50 years of age who have been diagnosed with schizophrenia and are either nonsmokers or current smokers (at least 10 cigarettes per day for the past year). * Current smokers must be able to give up smoking for 48 hours. Design: * This study involves an initial screening visit and up to five study visits. * After the screening visit, participants will have two sessions in which they will complete questionnaires about thoughts, memory, and smoking habits. Smokers will also have nicotine blood and carbon monoxide breath levels taken during these sessions, before and after smoking a cigarette. * Participants will have sessions with imaging studies (e.g., magnetic resonance imaging) to provide baseline measurements for later tests, and will also have tests to measure brain electrical activity. * Participants will have a positron emission tomography (PET) scanning session to examine the nicotine receptors in the brain. Participants will need to stay overnight (nonsmokers) or for 2 nights (smokers) as an inpatient before the session. The PET scan session will take up to 6 hours, although participants will only be in the scanner for up to 3 hours. * Participants will have a follow-up phone call with study researchers 1 week after the PET scanning session.
NCT00728741
This study will locate areas in the brain that help people devise action plans to carry out complex tasks requiring use of strategy. The ability to plan strategically is impaired in patients who have had a stroke affecting the front parts of the brain. This study will use functional magnetic resonance imaging (fMRI) to examine the activity of different areas of the brain during the formulation and execution of plans. Right-handed healthy volunteers between 18 and 60 years of age may be eligible for this study. Participants come to the NIH Clinical Center four to five times to complete the following procedures: Visit 1 - Screening * Medical history * Physical and neurological examinations Visit 2 - MRI brain scan (if one has not been done within the past year) MRI - This test uses a strong magnetic field and radio waves to obtain images of the brain. The scanner is a metal cylinder surrounded by a magnetic field. The subject lies on a table that can slide in and out of the scanner, wearing earplugs to muffle loud noises that occur during the scanning. Visits 3 to 5 - Task training sessions and two fMRI scans Functional MRI involves taking MRI scans while the subject performs a task in order to learn about changes in brain regions that are involved in the performance of the task. Subjects are trained in two tasks (see below) and then perform the tasks while in the MRI scanner. * Task 1: The subject presses computer keys in response to the direction of arrows shown on the computer screen. The keys are pressed according to a given set of rules the subject is taught. * Task 2: This task is similar to task 1, but the subject is also asked to remember certain previous actions and responses.