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NCT01266577
Background: \- Magnetic resonance imaging (MRI) is a widely used scanning technique to obtain images of the human body and evaluate activity in the brain. A particular MRI method called magnetic resonance spectroscopy (MRS) can be used to study brain chemistry as well, which may help researchers who are studying new treatments for psychiatric illnesses. Researchers are interested in improving current MRI and MRS techniques, as well as developing new MRI and MRS techniques to view and measure brain chemicals and brain activity. Objectives: \- To implement, develop, and optimize brain chemistry imaging techniques using magnetic resonance imaging and magnetic resonance spectroscopy. Eligibility: \- Healthy individuals between 18 and 65 years of age. Design: * This study will involve a screening visit and a scanning visit at the National Institutes of Health Clinical Center. * Participants will be screened with a full medical and physical examination, blood and urine tests, and neurological testing. * During the second visit, participants will have an MRI scan of the brain. (Participants who have received an MRI within the past year will not need to have a second one; the images of the previous scan will be used for this study.) All participants will then have an MRS scan using the same scanning equipment.
NCT00884702
Background: * The brain needs sleep to function normally, but the purpose of sleep is not understood. Brain activity decreases during sleep, so it may be that sleep is important to maintain, repair, or reorganize brain cells. In animals, the formation of brain proteins increases during sleep, and the same thing may happen in humans. * There is also evidence that learning and memory are helped by sleep, and that the synthesis of proteins in the brain are involved. Objectives: * To examine the formation of proteins in the brain while people are awake, deprived of sleep, and during sleep. * To look at the formation of proteins in the brain while awake or asleep and following learning a task. Eligibility: * Healthy volunteers between 18 and 28 years of age. * Volunteers must not have psychiatric, neurologic, or sleep disorders or certain types of vision problems, and must be able to undergo imaging studies. Design: * Study Part I (protein formation in waking, sleep deprivation, and sleep): * Participants will wear an actigraph (a unit to record motor activity) for 2 weeks prior to admission. * Participants will have physical and psychological examinations, along with a blood sample. * After admission participants will have three positron emission tomography (PET) scans to study protein formation and one magnetic resonance imaging (MRI) scan over the course of two days. * Participants may be asked to stay awake for as long as 20 hours and will be monitored throughout. * Participants will be able to sleep overnight after they complete the required scans and monitoring, and will be discharged the following morning. * Study Part II (protein formation in waking and sleep combined with a learning task): * Participants will wear an actigraph (a unit to record motor activity) for 2 weeks prior to admission. * Participants will have physical and psychological examinations, along with a blood sample. * After admission participants may be asked to stay awake for as long as 20 hours and will be monitored throughout. * The next morning, participants will be trained to perform a computerized visual discrimination task, and will be tested 8 hours later (after sleep or after remaining awake) on the visual discrimination task. * Some participants may have PET and MRI scans as part of the study. * Participants will be able to sleep overnight after they complete the required tests and scans, and will be discharged the following morning. * Participants will receive financial compensation for their participation in these studies.
NCT01195961
Background: \- Developmental dyscalculia is a learning disability in which individuals have difficulty learning or comprehending mathematics or other number concepts (such as keeping score during games, measuring time, or estimating distance). Developmental dyscalculia affects certain parts of the brain that are required for processing numbers. Research has shown that a form of brain stimulation called transcranial direct current stimulation (tDCS), applied when healthy individuals are being trained to carry out tasks with numbers, improved the ability to process numbers and solve math problems. More research is needed about whether tDCS can improve number processing in people with developmental dyscalculia. Objectives: \- To examine whether the effects of transcranial direct current stimulation can help individuals with developmental dyscalculia perform mathematical calculations. Eligibility: \- Individuals between 18 and 50 years of age who have been diagnosed with developmental dyscalculia, or are healthy volunteers without dyscalculia. Design: * Participants will have a screening visit and seven study visits. The screening visit and six of the study visits will take place consecutively over the course of 6 days, and the final visit will take place 3 months after the initial participation. * Participants will be screened with a medical history, physical and neurological examination, and a brief examination to test for dyscalculia and determine the participant's dominant hand. * Participants will be randomly assigned to one of two groups for the study. One group will receive tDCS during training to perform a task with numbers, and the other group will receive the same training with sham stimulation. Participants will not know which group they are in. * During the study visits, participants will be trained on number tasks on 6 consecutive days. Before the tDCS or sham stimulation is applied at the beginning of the experiment and at the end of each training day, participants will perform other tasks with numbers. Participants will be evaluated based on the accuracy and speed with which they respond to the questions. * At the followup visit, participants will perform the same number tasks they completed during the study visits. No tDCS will be performed at this visit.
NCT00001926
The purpose of this study is to test the belief that specific areas of the brain are connected differently in blind patients than patients with sight. In addition, the study will examine the different anatomical connections between brain areas of patients who became blind early in life versus patients who became blind later.