2. Subject has an established close relationship of at least 6-months duration before screening (Visit -1) with an informant who will be able to observe and be willing to report on the subject's behavior and symptoms in multiple social settings during the course of the study. Informant is defined as a person who has a domicile relationship with the subject. When applicable, the informant should be the subject's spouse/significant other. Additionally, the informant cannot participate as a subject in the study and can only serve as the informant for a single subject.