A fMRI(Functional Magnetic Resonance Imaging) Research Study to Learn More About Multiple Sclerosis and Individuals Potentially Experiencing Memory Difficulties

Inclusion Criteria: Between 18 and 65 years of age and experiencing some forgetfulness Diagnosed with MS, currently taking Rebif® and experiencing mild memory problems Participants will have stable medication dosages 1 month prior to testing With no past or present neurological disorders (e.g. head trauma, seizures, encephalitis, stroke) except MS With no known medical illnesses (e.g. diabetes, uncontrolled hypertension, arthritis) With no psychiatric illness With no current substance abuse Females should not be pregnant or nursing With no metallic devices in the body or claustrophobia Exclusion Criteria: Previous history of CNS disturbance other than MS Severe motor or visual impairment that might interfere with the cognitive activation tasks Prescribed psychoactive medications Memory deficits caused by other significant neurological disease or psychiatric disorder Active malignancy within one year of study participation Known human immunodeficiency virus (HIV) Current diagnosis of unstable glaucoma; history of myocardial infarction Symptomatic Coronary Artery Disease within the last 12 months or evidence of ongoing ischemia or uncontrolled atrial or ventricular arrhythmias as shown by ECG; poorly controlled or labile hypertension History of epilepsy or other seizure disorder within the past 12 months Allergy or hypersensitivity to amphetamines or other sympathomimetic amines