Decision Making Deficits in Traumatic Brain Injury

Background: - People with a traumatic brain injury (TBI) can have trouble making the best possible decisions. Researchers want to learn more about the parts of the brain that control decision making. They also want to know how these are different between people. This may help predict how people make decisions after TBI. Objective: - To learn more about which parts of the brain are involved in making decisions and how decisions may be hurt after TBI. Eligibility: - Adults age 18 to 60. Design: - Participants will be screened with medical history and physical exam. They will also take memory, attention, concentration, and thinking tests. - Participants will do up to 2 experiments. - For Experiment 1, participants may have 3 scans: - PET: a chemical is injected through a thin tube into an arm vein. Participants lie on a bed that slides in and out of the scanner. - MRI: a strong magnetic field and radio waves take pictures of the brain. Participants lie on a table that slides in and out of a metal cylinder. It makes loud knocking noises. Participants will get earplugs. They might be asked to do a task. A coil will be placed over the head. - MEG: a cone with magnetic field detectors is lowered onto participants head. - After the scans, participants will perform a decision-making task. - For Experiment 2, participants will perform a decision-making task before and after receiving transcranial direct current stimulation (tDCS). - tDCS: wet electrode sponges are placed over participants scalp and forehead. A current passes between the electrodes. It stimulating the brain. - Participants will return 24-48 hours later to repeat the decision-making task.