When a decapitated flatworm regrows its head, it gets all of its old memories back, too. Source Source 2 Source 3

Photo: Journal of Experimental Biology, Shormat and Levin

Researchers trained the creatures to travel across rough surfaces to get food, and then cut off their heads. Two weeks later, when their heads had grown back, the worms remembered how to navigate the rough terrain to eat, just like they had before they were decapitated.