Physiology of Volition Studied With Nerve Block

Background: \- The experience of volition that accompanies voluntary movement can be divided into the sense of will, or deciding to move, and the sense of agency, or feeling that the movement just made was self-generated. Very little is known regarding the neurological origin of this sense of volition. Previous research has shown that a particular part of the brain, the parietal lobe, is involved in our inner sense that we control the movements we make. Researchers are interested in determining if this sense relies on sensory information from moving fingers reaching the parietal lobe. Objectives: \- To determine the brain regions responsible for the sense of volition and the associated sense of agency. Eligibility: \- Healthy right-handed individuals between 18 and 55 years of age. Design: * The study will involve a screening visit and two testing visits. The screening visit will last 30 minutes to 1 hour, and the testing visits will each last 3 to 4 hours. * Participants will be screened with a physical examination and medical history. * At each testing visit, participants will have a brain magnetic resonance imaging (MRI) scan, electroencephalography (EEG), and electromyography (EMG). The MRI scan and EEG will be done during a movement task that involves the thumb, second finger, and fifth finger of one hand. EMG will be used to monitor movements and muscle activity. * During the second testing visit, participants will receive a nerve block using anesthetic, followed by the MRI, EEG, EMG and movement task. The nerve block will temporarily numb and prevent the movement of parts of the hand and fingers. * After the MRI scan and EEG recording, participants will be asked to rate how much control they felt they had over choosing whether to move, and how much control they felt they had in actually making the movements.