Richard, I wouldn't call what I have dementia, but I have a very hard time speaking coherently when I'm going off medication, and/or stressed or tired. I'll know what/who I'm trying to say, but the words won't come. Extremely frustrating and depressing. Weirdly, (is that a word?) I can usually type OK, if I can get my fingers to work. You might check and try to find out if your dad is understanding, but not able to respond. bob