fMRI and NIRS Imaging for Traumatic Brain Injury

Background: \- The amount of blood flowing in brain areas goes up when those areas are being used for activities, such as movement or seeing. Functional magnetic resonance imaging (fMRI) is a common way of measuring blood flow in the brain. Near infrared spectroscopy (NIRS) can also be used to study blood flow in the brain. However, NIRS has not been used as often as fMRI. Researchers want to compare fMRI and NIRS to see whether they give similar results. These studies will be used to look at people who have had a traumatic brain injury. Objectives: \- To test how well NIRS measure changes in blood flow in the brain after a traumatic brain injury. Eligibility: * Individuals between 18 and 60 years of age who have had a traumatic brain injury. * Healthy volunteers at least 18 years of age. Design: * Participants will be screened with a physical exam and medical history. Researchers may ask to see brain images during from previous MRI scans. * Participants will have a NIRS scan of the brain. They will be asked to do certain tasks while inside the scanner. These tasks will involve responding to images that appear on a screen. * Treatment will not be provided as part of this study.