Decapitated Worms Regrow Heads, Keep Old Memories

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.

Researchers decapitated a flatworm (left), and then allowed its head to regrow (far right). Photograph courtesy Michael Levin and Tal Shomrat, Tufts University

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.

Carrie is a freelance science writer living in Virginia. When she's not writing about cool critters, she's spending time outside, drinking coffee, or knitting. You can visit her website at http://www.carriearnold.com
  • Ima Ryma

    When humans found us flatworms can
    Lose our head then grow it back.
    All kinds of experiments began,
    So many on me – I’ve lost track.
    The latest – getting me to go
    Into the light which I avoid.
    Predators see me – doncha know!
    Humans stuck food there, I enjoyed.
    I think okay. They chop my head.
    Two weeks later a new head grew.
    I went to the light to get fed.
    It was food and safe. I just knew!

    I remember food, but don’t ask me
    When’s my wedding anniversary.

  • Douglas Raybeck

    Very encouraging. Perhaps my elbow knows where my car keys are?

  • Chris Williams

    This must be muscle memory.
    Try a change of terrain and see if results are replicated.

  • Felipe heba

    Genial. Que interesante

  • Bill

    This was known at least 50 years ago! What’s new about it now?

  • robert easterbrook

    Just watch, some idiot will say this research is linked to the study human brains and human memory. :i

  • charith

    but in the experiment scientists have assumed brain functions always limited to head. Majority of cases brain functions limited to heads especially in mammals. We still dont know whether those animals have memory cells which act completely differ from the usual animals. May be the memory cels of this animal situated everywhere in the body. Any way this is a very important experiment.

  • kevin Guthrie

    It has been long suggested that memory of many animals are contained in the genes. A previous test was done with a black bird or raven, can’t remember which. The bird was bound to be wingless and put in a maze till it found its way out, then after breeding the young was placed in the same maze and found its way out without fail. It might be a possibility that because humans are capable and do absorb so much information over such a long time that there simply is no room for it all in are own genes, providing that we have the same feature. Specially considering how every human can have such an array of personal features both physically and mentally, that much like the class room one can never place a single set of guidelines/instincts for us to follow. That any attempt to do so has only met with with death and exstinction in short order.

  • Suraj Singh

    Fascinating discovery.
    Thank you for sharing the knowledge. A simple experiment to some unanswered questions, can now be relooked as to what humanity is all about physcologically and physiologically.

  • mei

    wow, it’s really interest. I know something like earthworm or lizard regrow their body or tail, but this is totally different- regrow a head with memory. All I want to say is I have great esteem for your work.

  • Amy Baron

    These are not worms like earthworms. They are flat worms called planarians.

  • Spring

    Ancient Egyptians believed the stomach was the seat of the brain, so some ancient cultures knew that the brain is not the only source of memory.
    All cells contain DNA, the guide for making all animals and plants. DNA works by making RNA, which stores our memories as proteins. Since all cells make RNA, they probably all have memory. They need it to “remember” what they are supposed to do and how to do it. If we learn to access those memories maybe we can retrain cells to perform other functions, like “teaching” a fat cell to make insulin when the pancreas doesn’t make enough of it, or retraining insulin cells to make better, more usable insulin. There’s a series of research projects at least equal to mapping human DNA.

  • Nilufa Nizar

    amazing! may be in the future we could find a cure to the Alzheimer, and this shows how important worms are

  • Nilufa Nizar

    I mean the worms are given another chance to survive, so they can finish the task fixing the Eco cycle

  • Jaysham

    It is possible as duck can fly without head after the head is choped away.

  • Ian Brown

    I once was accused of being stupid and had no brains and I have to say i just lost the head with them. lol. seriously though I think this is amazing and should be studied further, I believe the soul holds all our information so when we die we its not entirely the end if you see what i mean, I think I am saying that I believe in the afterlife. regards Ian Brown

  • Rob Crampton

    This is old news. If you were to talk to any John Barnes Myofascial Therapist, we could tell you that already. When we release the fascia, our patients remember old memories long forgotten. Fascia is throughout our entire body. You’d be surprised how much the body can remember……

  • Chris Fisher

    Cool stuff, and is this post by Rob Crampton for real? I hope not…because it is….soooo…stupid.

  • Heather

    I also read how the human digestive system has a large amount of nerve tissue and has actually been referred to as a second brain.

    The digestive tract would have evolved early in most species, so this is where I would look in these worms for the source of this retained memory!

    I would suggest they run the same tests they did to confirm the retained memory on the worms that resulted from the regenerating heads they severed off the bodies.

  • Joao

    I think what happends here is that the brain processes the situation but then sends a specific signal to the body, which delievers a response that can be modulated by feed back. Emotions are, in humans too, organic responses, and very primitive ones at that. What changes the behavior of the worm is the associated emotional response, rather than a memory. I think what we have here is predicted by neurologist Antonio Damásio works. Exciting discovery.

  • Oguz Ceylan

    Proof of soul 😛

  • Robert Gray

    Rob, what do you mean by “release the fascia”? And what part of the body do you release the fascia in that brings back memories in patients?

  • Suraj

    I dont understand…
    “Then the team showed the worms with the regrown heads where to find food, essentially a refresher course of their light training before decapitation.”

    It says they were retrained to find food. So where is the memory coming into play? Its basically new memory right? Or did they conduct other experiments where there were no re-training?

  • John

    I had the same thought as Suraj- to prove anything you’d have to compare the “retrained” (and re-headed) worms with worms that were not exposed to the initial training, but were given the same “retraining”. That’s a critical step, and without it you’ve only proven that the re-headed worms are as good as the worms that had the initial and re-training, but weren’t beheaded, which could happen if the (non-beheaded) worms forgot the initial training in the interim.

  • Aliya Ivlow

    Why would you decapitate a worm?

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