1. Functional Magnetic Resonance (fMRI): brain BOLD fMRI - blood oxygen level dependent fMRI - harnessing the magnetic properties of the ferric ion of hemoglobin to image changes in blood flow to metabolically active brain loci. The underlying assumption of the imaging modality (similar to Positron Emission Tomography) is the metabolic coupling of cellular activity and blood flow. Analyses will focus but will not be restricted to subthalamic structures involved in the RAS.