Additional Study Information: The purpose of this study is to better understand how to manage behavioral symptoms of frontotemporal dementia over time. These symptoms include agitation, aggression, and repetitive behaviors. During the study, we will give the participant low doses of lithium carbonate, or a placebo (sugar pill). Over the course of three months, the participant will come in every two weeks with a study partner, who may be a family member or friend, for medical assessment. Each visit will last 1-2 hours. Participation and transportation costs will be reimbursed.