5. Contraindication to MRI/ MRS scanning, including pacemakers or other implanted electrical devices, brain stimulators, some types of dental implants, aneurysm clips (metal clips on the wall of a large artery), metallic prostheses (including metal pins and rods, heart valves, and cochlear implants), permanent eyeliner, implanted delivery pump, or shrapnel fragments. Patients requiring low dose oral lorazepam for mild to moderate claustrophobia will be allowed to participate.