- Participants must have a reliable informant (relative, partner, or friend). The informant must be willing to participate as a source of information and has at least weekly contact with the participant (contact can be in-person, via telephone or other audio/visual communication). The informant must have sufficient contact such that the Investigator feels he/she can provide meaningful information about the participant's daily function. If possible, an alternate informant meeting these criteria who can replace the primary informant should be identified prior to randomization