Evaluate the Effect of Switching From Daily Injections of 20mg Glatiramer Acetate (GA) to 40mg GA Three Times a Week in Subjects With Relapsing-remitting Multiple Sclerosis

The primary aim of this study is to observe the effect of switching from daily injections of 20mg glatiramer acetate (GA) (20mg/daily) to GA 40mg three times a week (40mg x 3/weekly) on thalamus pathology, as measured by changes in diffusion-tensor imaging (DTI) in patients with relapsing-remitting multiple sclerosis (RRMS). We hypothesize that GA 40mg x 3/weekly will exert similar, if not better effect on prevention of thalamic pathology, as compared to GA 20mg/daily. The secondary objective of this study is to investigate the effect of switching from GA 20mg/daily to GA 40mg x 3/weekly on evolution of microstructural changes in normal appearing white matter (NAWM) and normal appearing gray matter (NAGM), as measured by DTI.