If you are a healthy female and 42-55 years of age: The Neurophysiology of Movement Laboratory on the Boulder campus is conducting a study evaluating brain activity and fatigue to potentially benefit persons with multiple sclerosis. The study will involve three visits in Boulder on separate days: • Visit 1 (~ 30 minutes in duration): Complete cognitive test • Visit 2 (~ 1-2 hours in duration): Several tests of motor and cognitive function • Visit 3 (~1 ½ hours in duration): Brain imaging using magnetic resonance imaging (MRI)