Nature
Two-thirds of an octopus's neurons live in its arms, not its brain
An octopus has roughly 500 million neurons, about as many as a dog, but only 40 to 45 million sit in its central brain. The rest run along nerve cords down each arm, so a severed arm can still reach, grip and recoil from a painful touch on its own. Each arm can taste what it touches and make local decisions while the brain handles the bigger picture.