In French Revolution-style, researchers decapitated flatworms—then did something that would give even Madam Defarge the creeps. 
 
 The scientists let the worms’ heads grow back and found that their memories returned along with the new noggins, according to a new study in the Journal of Experimental Biology. 
 
 Michael Levin and Tal Shomrat, biologists at Tufts University, have been studying how animals store and process information, whether it’s memories in the brain or the blueprint for developing organs in the body. 
 
 The team turned to flatworms because, despite their relative simplicity, they have many of the same organs and body organization as people: a brain and nervous system, bilateral symmetry, and even some of the same behaviors. 
 
 Flatworms “also have many of the same neurotransmitters as we do, and have been shown in older studies to remember complex tasks,” Levin said. (Read more about memory in National Geographic magazine.) 
 
 Yet unlike people, these worms have a remarkable ability to regenerate organs and body parts, including their brains—making them perfect research subjects. 
 
 In the Spotlight 
 
 Planarian flatworms are a hugely diverse array of small non-parasitic worms found in both freshwater and saltwater environments. 
 
 They have primitive eyes that can detect light, which they generally avoid—being in light makes them more obvious to predators. 
 
 To train the worms that lighted areas were safe and contained food, the researchers used a computerized device to continually track the worms’ behavior, providing rewards when a worm ventured into the bright spots and punishments when it remained in the dark. 
 
 “We used this device to get worms used to a dish with a peculiar laser-etched surface. When they remember this surface, they will rapidly approach a piece of liver to eat it, as opposed to spending much time circling around the dish to get the lay of the land,” Levin said. 
 
 Off With Their Heads 
 
 After the team verified that the worms had memorized where to find food, they chopped off the worms’ heads and let them regrow, which took two weeks. 
 
 Then the team showed the worms with the regrown heads where to find food, essentially a refresher course of their light training before decapitation. 
 
 Subsequent experiments showed that the worms remembered where the light spot was, that it was safe, and that food could be found there. The worms’ memories were just as accurate as those worms who had never lost their heads. (Test your memory with a National Geographic game.) 
 
 Memory Beyond the Brain 
 
 The obvious question remains: How can a worm remember things after losing its head? 
 
 “We have no idea,” Levin admitted. “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.” 
 
 Researchers have long confined their investigations of memory and learning to the brain, Levin said, but these results may encourage them to look elsewhere. (Read about a tadpole that can see through an eye implanted on its tail.) 
 
 “We’ve established a new model system in which our future work will be able to figure out how memories get encoded and decoded to and from living tissues.” 
 
 And given that we can’t regrow their heads, it’s unlikely that decapitation will ever become a serious memory aid for frantic students before exams. 

 Animal Loses Head But Remembers Everything 
 
 When I first saw this," says cell biologist Alejandro Sanchez Alvarado, "it was with total amazement." 
 
 Robert Krulwich/NPR 
 
 This is a worm. It's called a planarian. It's about an inch long, and you'll find it gliding along the bottoms of rivers and ponds all over the world. It's very flat, like a moving bit of pasta — nothing special to look at, but it has a hidden talent that has made it famous. It can regrow its body parts better than almost any other animal on Earth. So if by some chance something bites its head off ... 
 
 Robert Krulwich/NPR 
 
 ... or removes its tail, or zaps its head and its tail simultaneously ... 
 
 Robert Krulwich/NPR 
 
 ... the dangling middle piece will, within a couple of weeks, grow both its front and its back to full size. Meanwhile, the severed head, if left alone, will also generate a full-sized new worm. The lonesome tail will do that, too, so where you started with one worm, you'll now have three. This worm likes to regenerate. 
 
 Robert Krulwich/NPR 
 
 You can even remove a single, special cell from an adult planarian (not an infant cell, but a cell taken from a mature adult), and from that one cell, scientists discovered a few years ago, the worm can regenerate a whole new creature — the skin, guts, nerves, muscle, eyes, mouth, everything. It will be genetically identical to the donor. 
 
 Robert Krulwich/NPR 
 
 How do they do this? How does a random slice of worm (often with no brain, just a clump of meat, says Alvarado — "I mean, really, it's a piece of flesh") figure out where its front is, where its bottom is? Clearly, this is a genetically driven talent, but do we know which genes, how many genes are involved? 
 
 No, we don't. Intriguingly, we share a bunch of genes with these flatworms. If we ever figure out how they do it, we might be able to pick up a few of their tricks, which are astounding to see. Just click below, in a video from San Francisco's Exploratorium, to watch a severed head grow back a body, and — my favorite — see a worm sliced down the middle like a banana split create its other half. Professor Alvarado is the swooning narrator. 
 
 But we haven't gotten to the most remarkable part. Two biologists at Tufts University, curious to learn how this little worm remembers things, decided to do an experiment. 
 
 Michael Levin and Tal Shomrat know that planarians don't like light. In the dark, the worms can hide from predators, feel safe and skulk about gathering food. They have those two weird little eye cups — angled, so they seem to be cross-eyed — so these worms can detect light. And when they do, they normally scuttle off (or, in my imagination, cover their eyes). 
 
 i Robert Krulwich/NPR Robert Krulwich/NPR 
 
 But Levin and Shomrat wanted to implant a memory in their laboratory worms, and the memory they decided on was, "Light's OK. Good things happen when you go to lit spaces." To do that, they placed a delicious liver snack on a well-lit plate, and rewarded the worms who ventured close (and punished them if they sought the safety of the dark). So, gradually, their worms began to trust the light, and venture in more quickly. 
 
 Robert Krulwich/NPR 
 
 Then (sorry PETA), they chopped off their heads. That would be mean if they were chopping off, say, Marie Antoinette's head. But remember, these are planarians, so in a couple of weeks the beheaded worms had new heads. What Levin and Shomrat wondered was, did those new heads keep their old memories? 
 
 Yes they did! 
 
 According to National Geographic's account, after a short refresher course, these worms-with-new-heads "remembered where the light spot was, that it was safe, and that food could be found there. The worms' memories were just as accurate as those worms who had never lost their heads." 
 
 Robert Krulwich/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." 
 
 The unanswered questions here are so fascinating. "When I see a planarian," says Professor Alvarado, "I just see a big void of mystery." How does an animal know how to build itself? Is there a body plan in the brain? In our cells? Which cells? What triggers those cells? Could we ever do this? Could we ever build what the worms have into ourselves? Questions, questions, questions and, so far, hardly any answers. 
 
 But the worms — they know. 
 
 The mysteries of the planarian are so cool, there's a "regeneration" T-shirt that celebrates these worms. I found it here.
– Ever heard of planarians? These inch-long worms are famous for their remarkable ability to regrow body parts that get cut off. Slice one worm into three parts—head, body, and tail—and each part will regrow the rest of the worm. From one planarian, you get three! How they do it we don't know, but two biologists at Tufts University conducted an experiment to test whether a decapitated planarian could retain its memories, NPR reports. Knowing that planarians shy away from the light, Michael Levin and Tal Shomrat lured them into lit areas with tasty liver snacks until they got comfortable with light. Then the scientists cut off the planarians' heads. When each body grew back a head, lo and behold, the worms remembered that lit areas were safe and had good food. So how did the bodies regrow heads with that memory? "We have no idea," Levin told National Geographic. "What we do know is that memory can be stored outside the brain—presumably in other body cells," and memories "can get imprinted onto the new brain as it regenerates."