This is a double-blind, placebo-controlled, crossover study testing whether Vyvanse (lisdexamfetamine; LDX) improves executive functioning (EF) in 100 postmenopausal women who report onset of EF difficulties after oophorectomy. This study involves magnetic resonance imaging (MRI) to see how LDX affects brain chemistry while undergoing two 6-week trials of the study drug and placebo capsules.