Researchers transferred gut bacteria from old mice to young, healthy animals. The result was clear: the young rodents suddenly performed just as poorly on memory tests as their elderly counterparts https://www.nature.com/articles/d41586-026-00768-6 Gut bacteria influence memory https://www.fr.de/wissen/wahrscheinlich-auch-bei-menschen-darmbakterien-beeinflussen-das-gedaechtnis-zr-94218486.html