The planarian is just a little, flat worm that lives in dark places, like the bottom of ponds. It has one secret skill, though, and it’s a good one: The planarian is incredibly good at regenerating. It can grow back its tail. It can grow back its head. It can grow back its body from either of those shorn-off bits. If you snip off both its head and tail, one worm can become three worms. And all three may share the same memories.
A group of scientists taught these dark-loving flatworms to approach the light rather than flee from it — they baited a patch of light with liver, and over time the worms learned that this particular bit of light was safe and full of tasty food. Then the scientists chopped off their heads. The bodies grew new heads — and the new heads still knew that the light was good.
As Robert Krulwich puts it at NPR:
So these worms grew new heads with old memories, a remarkable finding, particularly when you consider it took 14 days or so for the head to grow back. How’d the worms do it? Once again, “We have no idea,” Michael Levin told National Geographic. Since these animals were briefly brainless after their decapitation, he says, “What we do know is that memory can be stored outside the brain — presumably in other body cells — so that [memories] can get imprinted onto the new brain as it regenerates.”
New year’s resolution: Learn how to do that shit in 2014.