View clinical trials related to Normal Physiology.
Filter by:The goal of this interventional study is to develop an individualized approach using transcranial magnetic stimulation (TMS) in a high-precision manner. This approach will use TMS to modulate brain activity at multiple locations simultaneously. Functional magnetic resonance imaging (fMRI) and electroencephalograph (EEG) will record the responses and guide the stimulation. Specifically, the placement and orientation of TMS coils will be tailored to stimulate the targeted functional brain areas informed by fMRI. To maximize the interventional effect, stimulation pulses will be delivered based on EEG oscillations.
The goal of this clinical trial is to learn how the pupil responds to different light stimuli and how that relates to sleep and daily rhythms in healthy people of different ages. The main questions it aims to answer are: - Does the eye's pupil response to light stimuli differ by the sex and age of the participant? - Is the eye's pupil response to light stimuli related to each participant's sleep timing, their body clock timing, and their hormone responses to light. Participants will have a special eye exam and complete questionnaires before starting the study to see if they can participate. If they can participate, they will wear a special watch that monitors their activity and light levels for one week. Then they will live in a research room at the Mass General Hospital for 3 days/2 nights during which we will test their pupil response to light, their body clock timing, and their hormone responses to light.
Background: Substance use disorders (SUD) can be considered disorders in the way people process incentives, learn, and make decisions. To understand why some people develop SUD, researchers need to develop reliable tests that show how people think and learn. This natural history study seeks to develop a set of tasks that could then be used to test how people learn and make decisions. Objective: To develop and validate behavioral tasks that could be used in future studies. Eligibility: Healthy people aged 18-45 years from the Baltimore area. They must also be enrolled in protocol 06-DA-N415. Design: Participants will perform different tasks. Most tasks require 1-4 study visits; some may require up to 12. Visits are 1-14 days apart. All visits will last about 1-7 hours. Participants will perform tasks on a computer. As they work they may be given different stimuli: Smells. Participants will sniff odors through a plastic tube or mask on their nose. Flavors. Participants will wear a mouthpiece and small amounts of different flavored liquids will be placed in their mouth. Pictures. Participants will look at different images. Sounds. Participants will wear headphones and various sounds will be played for them. Food. Participants may be asked to eat a meal before, during, or after a task. The researchers will provide the meal. During each task, participants will wear sensors to monitor their heart rate, blood pressure, breathing, and other physical changes in their bodies. Some participants will have a functional magnetic resonance imaging (fMRI) scan. They will lie on a table that slides into a cylinder. They will perform tasks on a computer screen during the fMRI.
Background: Laboratory tests that use blood and urine can provide a great deal of information about human health and disease. To develop even better tests and to improve the ways samples are handled for testing researchers need to experiment with samples from healthy people. Objective: This natural history study will collect blood and urine from healthy people. The samples will build a repository that will be used for all kinds of research. Eligibility: Healthy people aged 18 years or older. Design: Participants will have 1 study visit. The visit will last up to 2 hours. Participants will be screened. They will answer questions about their health history. They will list any medications they take. They will consent to donate samples for research and future use: Blood: Up to 4.5 tablespoons of blood may be collected from a needle inserted into a vein. Urine: Participants will be given a sterile container to provide a sample. Some participants may be asked to provide other types of samples. Some participants may be asked to provide new samples if their first ones are depleted.
Background: Magnetic resonance imaging (MRI), which uses strong magnets to get images of structures inside the body, is a valuable tool in modern medicine. But researchers are always looking for ways to improve this technology. To better understand how to use MRI to diagnose problems, researchers need to collect more data from scans of healthy people. Objective: To get MRI scans of healthy people to improve the measurements doctors can make from the images. Eligibility: People aged 18 years or older in good general health. Design: Participants will be screened. They will have a physical exam focused on their nervous system. They will complete questionnaires. Participants will have at least 1 MRI scan. The target of the scan may be the brain, liver, prostate, breast, or other body part. Before the scan, participants will remove any metallic objects. They will lie on a narrow table that moves into a long, narrow tube. They may have special pads placed around them to help them remain still. Participants will hear loud noises during the scan. They will get earplugs or earmuffs to wear to muffle the sound. They can communicate with the MRI technician and will have an emergency button to squeeze at any time if they want the scan to stop. The scan will take up to 2 hours. Some participants may be asked to perform tasks on a computer screen during the scan. Participants may return for up to 5 scans in 3 months. Some may have as many as 30 MRI visits per year. They may remain in the study for up to 2 years....
Background: Diet-induced thermogenesis (DIT) is the amount of energy one s body uses to eat food, absorb the nutrients from the food, and process those nutrients. Researchers would like to understand more about how changing the balances of protein, fat, carbohydrates, and total calories in the diet can affect DIT. Objective: To learn how different diets can change a person s DIT. Eligibility: Healthy people aged 18 to 60 years who have not intentionally lost weight in the past 6 months. Design: Participants will stay in a clinic for about 34 days. They will eat only the food provided. They will receive 8 different diets during the study, including 7 test diets. Participants will undergo multiple tests. They will be screened with blood and urine tests and a test of their heart function. During the first few days: Their waist, thigh, and neck circumference will be measured. They will have a DXA scan: They will lie on a padded table for about 20 minutes while an instrument measures the amount of fat in their body. They will be tested for diabetes. They will answer questionnaires about topics including eating behavior, hunger, and stress. Throughout the study: Their weight will be measured daily. Blood tests will be repeated. They will stay in a metabolic chamber a total of 9 times. They will remain in a closed room for 24 hours while researchers monitor the room temperature and levels of oxygen and carbon dioxide. Participants will collect all their urine for each 24-hour period. ...
Background: Nicotine dependence leads to about 480,000 deaths every year in the United States. People with major depressive disorder (MDD) are twice as likely to use nicotine compared to the general population. They have greater withdrawal symptoms and are more likely to relapse after quitting compared with smokers without MDD. More research is needed on how nicotine affects brain function in those with MDD. Objective: To understand how nicotine affects symptoms of depression and related brain function. Eligibility: People aged 18 to 60 years with and without MDD who do not smoke cigarettes or use other nicotine products. Design: Participants will have 2 or 3 study visits over 1 to 3 months. Participants will have 2 MRI scans at least 1 week apart. Each scan visit will last 5 to 7 hours. At each scan, they will have urine and breath tests to screen for recent use of alcohol, nicotine, and illegal drugs. Before each scan, they will take 1 of 2 medications: nicotine or placebo. Participants will receive each medication once. They will not know which medication they are receiving at each scan. For each MRI scan, they will lie on a table that slides into a cylinder. Sometimes they will be asked to lie still. Sometimes they will complete tasks on a computer. Tasks may include identifying colors or playing games to win money. Each scan will take about 2 hours. Participants will answer questions about their thoughts, feelings, and behaviors before and after each scan. They will have a blood test after each scan.
Background: Scientists have long used simple measures (such as height and weight) to estimate how much a person s body uses food (calories) as energy, as commonly called the metabolic rate. But metabolism varies among people with similar body sizes. Scientists now believe the old formulas for estimating metabolic rates may not work well for all people. Researchers want to find more accurate ways to measure a person s metabolism. Objective: This natural history study will examine the relationships between metabolism, body composition, and body surface area in a wide range of people. Eligibility: Healthy children and adults aged 2 years or older. Also, people aged 2 years or older with conditions that may alter metabolism. These may include diabetes, obesity, renal disease, or cancer. Design: Participants will spend 2 days and 1 night in the hospital. They will provide a medical history and answer questions about their activity levels, the foods they eat, and their lifestyle. They will also eat a special diet. Participants will undergo many tests: They will lie in a bed with a clear hood covering their head for 30 to 45 minutes to measure the gases in their breath. They will lie on a padded table for about 15 minutes while their body is scanned. They will stand on a platform while a 3D scanner measures their body. They will have a test to measure how fast an electric signal moves through their body. They will grip an instrument to measure the strength of their hands. They will drink salty water and provide blood and urine samples. Participants may be invited to return for these 2-day visits up to 8 times per year. Return visits must be at least 2 weeks apart.
Background: Irritability is an elevated proneness to anger. Children with irritability have difficulty tolerating frustration. They get angry and have temper outbursts more easily than their others their age. Irritability is a symptom of DMDD and ADHD. (DMDD is disruptive mood dysregulation disorder. ADHD is attention deficit/hyperactivity disorder.) Yet the reasons why some children get irritated easily are not well understood. Objective: To use brain imaging methods to study responses to frustration in youth. Eligibility: Youth aged 8 to 17 years with severe irritability (including those diagnosed with DMDD) and/or ADHD. Healthy volunteers are also needed. All participants are already enrolled in studies 02-M-0021 or 01-M-0192. Design: Participants will visit the clinic 3 times. The second and third visits will be 3 to 4 weeks apart. The first visit will be an enrollment visit. They will receive training on the tasks they will do during the study. Participants and their parents will take surveys. They will answer questions about their moods and feelings. Participants will train for an MRI scan. They will lie in a mock scanner tube and hear the noises an MRI makes. On the second and third visits, participants will have real MRI scans. They will play a computer game or watch a movie during each scan. The scans will last about 1 hour. The week after each scan, participants will wear a device on their wrist to measure their heart rate and activity level. Participants and their parent will use a smartphone to answer questions about how they are feeling and acting. Participants who do not have smartphones will be given one to use during the study.
Background: Current techniques used to measure the health and function of a person s nerves and muscles are generally effective, but they do have limits. Researchers are looking for ways to improve the ability to observe nerves and muscles and how they function in this natural history protocol. Objective: To study the use of ultrasound (sound waves) to learn more about nerves and muscles. Eligibility: Healthy adults, aged 18 and older, with no history of stroke, nerve or muscular disorders, or spine surgery are also needed. A smaller population of adults aged 18 and older who have a neuromuscular disorder or show symptoms of nerve or muscle disorder will also be evaluated. Design: Participants will be screened with a medical record review. Participants will have up to 5 outpatient clinic visits. Most participants will have 1 or 2 visits. Visits will last for less than 3-4 hours each. During each visit, participants will give a brief medical history and have a physical exam. Participants will have ultrasounds to get pictures and measurements of their nerves and muscles. Gel will be applied to their skin. A probe will be placed on the skin surface. Sound waves sent through the probe will be used to create pictures. Participants may have nerve conduction studies. Wires will be taped to the skin surface near a muscle or nerve in the arm or leg. The nerve will be stimulated with a small electric current that feels like a rubber band flick. The response will be recorded through the wires.