The researchers aim is to investigate the effects of Tysabri on cognitive fatigue and on specific brain areas that have been shown to underlie cognitive fatigue in individuals with RRMS. The researchers will investigate the effects on the cognitive fatigue that develops during the performance of a demanding task and also on how cognitive fatigue changes as a function of duration of treatment.
The purpose of this research study is to investigate the effectiveness of Tysabri on cognitive fatigue in persons with Relapsing-Remitting Multiple Sclerosis (RRMS). Cognitive fatigue is the kind of fatigue that occurs after intense mental concentration as after a session of problem solving.