The advice you've heard a thousand times in zombie lore (dating back to the 1968 classic Night of the Living Dead), is that if you destroy the brain, you kill the ghoul. Not so in the case of the worm species known as the planarian, which can survive its own decapitation by growing a new head... and a new brain that can just start up where the dead one left off. Just think about that for a second.
As detailed in this article on The Verge, researchers at Tufts University found that the planarian's well-documented regenerative skills (it can grow new body parts if dismembered) include the ability to regrow a brain that can also retain the old brain's memories.
The scientists tested those memories by measuring how long it took the worms to reach food in a controlled setting, much like the way they train mice to navigate mazes. They discovered how decapitated worms that successfully re-grew heads (which is creepy enough) could re-learn their training after just a little practice. You know, kinda like Bub the zombie in Day of the Dead, re-learning how to use items like a phone, a razor... and a gun.
While more testing is needed to support the researchers' hypothesis, the data suggests that the worm's memories are stored somewhere else in its body. This may lead to a breakthrough in our knowledge of how memory functions, but we just can't help but wonder what this is going to do the whole “destroy the brain” rule when the zombie apocalypse finally arrives.