Are there any volunteer groups which pay visits to Alzheimer's patients for enrichment?

Both of my parents have dementia. My father has Alzheimer's. They live in an apartment with a full time care giver but he does nothing to enrich their lives. They just sit like lumps on the couch all day. They were thrown out of a wonderful assisted living place because my father kept threatening people. He's on medication now and much better. I worry that they don't have anything to keep their minds active. They won't even go anywhere when their caregiver offers to take them for a ride. I try to converse with them but it's like talking to people who don't have a grasp of English. My mom keeps repeating things and asks me the same questions over and over. My dad simply doesn't understand most of what is said. My mom also gets very anxious and scared that we will take dad away.