Yeah, it's a mouse study, but there are tons of human studies backing the whole gut-brain connection. There are even a bunch of books on it [1][2].

What's really cool is that the paper used low-dose capsaicin (just 5 μg/kg injected), and it completely restored hippocampal FOS activity and memory in older mice. Basically, that's the same stuff you get in cayenne pepper supplements - pretty easy to get your hands on.

[1] https://www.goodreads.com/book/show/28837738-the-mind-gut-co...

[2] https://www.goodreads.com/book/show/35210457-the-psychobioti...