I think my brain is atrophying. I have been going back and editing posts because I've made stupid typos or spelling errors. Even though I do (usually) proofread before I publish.
I haven't really had to use my brain much in a very long time. I've been out of school for almost five years, and there's little evidence I used my brain even when I was in school.
I try to keep it honed by reading a lot. And by doing sudoku and kakuro puzzles. Occasionally, I engage in a deep and intricate conversation. But I haven't really stretched my brain in ages. I don't know how to actually, it's just bored and it's making me feel slow and daft.