Eligible participants will be randomly assigned to receive the investigational medication or placebo. All study participants will take their assigned study medication twice a day for 12 weeks. Study participants will be asked to attend 7-8 study clinic visits for health exams and tests.
Caregivers will be asked to attend study clinic visits with the participant, as well as regularly monitor the participant's symptoms and answer questions about the participant.
During some study clinic visits, participants will look at a computer monitor and be asked to do a few simple activities.
Total participation in this study will last approximately 14-18 weeks.