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Decapitated Worms Regrow Heads, Keep Old Memories (blog.nationalgeographic.org)
283 points by sethbannon 1 month ago | hide | past | web | 70 comments | favorite

Study: An automated training paradigm reveals long-term memory in planaria and its persistence through head regeneration

Citation: Tal Shomrat, Michael Levin. Journal of Experimental Biology 2013. Published July 2, 2013

Link: http://jeb.biologists.org/lookup/doi/10.1242/jeb.087809

DOI: 10.1242/jeb.087809

Summary: Planarian flatworms are a popular system for research into the molecular mechanisms that enable these complex organisms to regenerate their entire body, including the brain. Classical data suggest that they may also be capable of long-term memory. Thus, the planarian system may offer the unique opportunity to study brain regeneration and memory in the same animal. To establish a system for the investigation of the dynamics of memory in a regenerating brain, we developed a computerized training and testing paradigm that avoided the many issues that confounded previous, manual attempts to train planarians. We then used this new system to train flatworms in an environmental familiarization protocol. We show that worms exhibit environmental familiarization, and that this memory persists for at least 14 days – long enough for the brain to regenerate. We further show that trained, decapitated planarians exhibit evidence of memory retrieval in a savings paradigm after regenerating a new head. Our work establishes a foundation for objective, high-throughput assays in this molecularly tractable model system that will shed light on the fundamental interface between body patterning and stored memories. We propose planarians as key emerging model species for mechanistic investigations of the encoding of specific memories in biological tissues. Moreover, this system is lik ely to have important implications for the biomedicine of stem-cell-derived treatments of degenerative brain disorders in human adults.

So the body grows a head back. Does also the head grow a body back, resulting in two worms?

I know totally nothing about these worms, but my armchair guess now is that the brain in the head is a visual center for those eyes, and the nerves in the body have the memory.

I hope they'll figure it out! And that they'll be able to map individual neurons like the 302 neurons of a Caenorhabditis elegans. And finally that they'll be able to simulate those neurons in software

In reply to your first question, according to wikipedia, yes.

...each piece has the ability to regenerate into a fully formed individual.

That's rather nightmarish. "Cut a worm in half. Now you have two worms."

Reminds me of the famous https://en.wikipedia.org/wiki/Lernaean_Hydra

What if you cut the top off the bottom you cut off of the old top? Now we're in Ship of Theseus territory. https://en.wikipedia.org/wiki/Ship_of_Theseus

I don't understand why this is considered a paradox.

It is only a paradox due to flawed thinking of what is considered the same. The problem is when you think of same object as a binary (it is same or it isn't). If you think of same object as a spectrum it becomes trivial.

In case of the mentioned ship, as individual pieces are replaced, what's same becomes smaller and smaller part of the entire ship. If you take these parts and build another ship, that will be the same ship that you originally had.

Thing is, considering an object as a spectrum leads to other problems. If continuous spectrum, then _any_ adjustment gives you a new object: e.g., a wave eroded a few atoms from the hull, now it's a new ship. If discrete spectrum, then same problem as before.

With the same memories that will then result in a pair of worms terrorizing you.

At some point a software engineer actually sat down and implemented a worm "torturing" algorithm.

I'm not a worm rights activist or anything, and the paper was a fascinating read, but man I'd hate to be a flatworm in these guys' lab. Makes me wonder if some dark agency somewhere in the world is using AI to perfect their autonomous human-torturing machine.

Maybe someone or something [0] already invented the perfect human-torturing machine and that’s what life is.

[0] https://en.wikipedia.org/wiki/I_Have_No_Mouth,_and_I_Must_Sc...

Check out Silent Weapons for Quiet Wars.


”At some point a software engineer”

More likely a Ph.D. student in biology. And, reading the paper, I get the impression the decapitation was still done manually. That must be a dangerous job, given that these animals have “a high tendency to undergo spontaneously fission” :-)

But yes, the paper doesn’t mention an ethics committee, so it appears the hunting season for flatworms is completely unrestricted.

Humanity is very good at torturing itself already.

There was a similar experiment where a research ground up flatworms and fed them to other flatworms and they learned the behavior faster. [1]

I suspect the worms aren't "learning" anything, but are simply adapting an inbuilt behavior based upon local conditions. If local conditions cause a hormone or epigentic shift, that would appear the behavior was learned and could be preserved when the brain was regrown. It would also explain how feeding the remains of other worms could "teach" it something. In reality it could just be an adjustment of hormone levels.

[1] https://en.wikipedia.org/wiki/Planarian#Regeneration

I was thinking that as I read it. Maybe their outer cells are just getting use to something and an evolutionary fitness mechanism keeps those other cells seeking whatever provides it nutrients.

I mean it get into the definition of what _memory_ is. When humans talk about muscle memory, we're not actually talking about memories actually being held in those muscles. We're just training our brain an nervous system to be faster and more precise at a given task.

When we train certain animals, their learning may have nothing to do with a central nervous system at all. And even the concept of "learning" could be a human personification we apply to an animals when really it is simply adapting or has some type of evolutionary fitness or propensity to repeat certain tasks that bring it food or warmth.

On a side node, I really dislike it when people say "our feet were designed to" or "this animal's webbed feet are designed to." I always try to say they "evolved to" or "adapted to." It's similar to when people say "It's suppose to rain all well," when you should really say, "They're predicting rain all week."

Yes! I sometimes wonder if Frank Herbert was aware of this study, reported in the press [1] three years before the publication of Dune, with its tales of transgenerational memory transmission and sandworms..

1: https://news.google.com/newspapers?id=BrgeAAAAIBAJ&%20sjid=R...

As a related story, meet Mike, the headless chicken.


For some reason i'm reminded of chicken little, the delicious chicken tissue growth from Frederick Pohl's The Space Merchants

A question comes to my mind: what could Mike the chicken not do without those "higher brain centres" the article mentions?

How long do you think Mike would have survived had he not been specially cared for?

My guess: barely long enough to die from dehydration.


Traumatic memories are accepted as sometimes being stored in some capacity in human body regions other than the head, I'd be very interested in seeing if this is connected, as research progresses.

Source: https://www.amazon.com/Body-Keeps-Score-Healing-Trauma/dp/B0...

I'd give my right arm to forget that trauma.

Meanwhile, this was posted on HN a few hours ago:

"Brain Cells Share Information with Virus-Like Capsules" Discussion/Link: https://news.ycombinator.com/item?id=16139798&ref=hvper.com

Maybe this is how the brain achieves back-propagation. This could explain how a headless worm grows back old memories (in other words, because the mechanism that allows it is infra-neuronal).

Funnily enough, I also wonder if, at least from an abstract and blurry viewpoint, this kind of "ambient" diffusion of information could explain why one could spot links from one paper to another like I just did. In this particular case, this is of course speculative but I think the idea i'm drawing on here can be particularly interesting, at least to a computer-science-minded audience like that of HN. If I were to give this idea the flesh supplement it lacks to make it more palpable, I would ask: what would it take for a theory of the way ideas form and diffuse to explain how itself has been formed and diffused ? My guess is that it requires the theory thinker to rephrase the question in this way "Where, thinking this idea will lead me to ?" if he ought to be able to explain not just what the ideation process is like but also how he has found himself caught in its loop. This is the question I'm asking.

The real feat here is that they convinced the worms it was safe to eat there even though they got their heads cut off.

Maybe they know, so they don't really care. :D

> Then the team showed the worms with the regrown heads where to find food, essentially a refresher course of their light training before decapitation

Would the worms remember without this “refresher course”?

Although I didn't read. I'd assume and hope they had some basic controls in place like an untrained worm decapitated and also a trained worm non decapitated

The experiment does not sound too good to me. They had to retrain the formerly decapitated worms. The article does not mention how much faster the "refresher course" trained the decapitated worms.

>Headless fragments regenerated from familiarized worms displayed slightly shorter feeding latency compared with headless fragments from unfamiliarized worms ... However, the effect was not statistically significant.

So, no. But they do better with the refresher course than other worms if I understand correctly.

>However, the effect was not statistically significant. //

AKA - there's no effect as far as we can tell without further experiment.

Correction: the paper (http://jeb.biologists.org/content/early/2013/06/27/jeb.08780...) is talking about the worms before re-familiarisation. They claim significance for previously "trained" worms being faster at picking up the training post decap+regen.

Sorry to be a bore, but does the brain of the flatworm have the same functions as that of the vertebrates? If an octopus, for example, has a "decentralised nervous system", I would not be surprised if it were the case with the worms.

I'm working on extending this work, now. For those of you interested in the history of memories outside of the brain, I would suggest reading the first chapter of 'The Golem: What Everyone Should Know About Science': http://cstpr.colorado.edu/students/envs_5110/collins_the_gol...

The idea of memory outside of the brain originated in the 1950s, when it was believed that memories may be stored in genetic material. This idea was discredited for interesting sociological reasons which the book explains well.

For those of you asking if the worm brain is a decent model: the work was done in planaria, which is the simplest organism known to have a centralized, two-hemisphere nervous system. So there really is a 'brain' up there in its head, the worm shows little behavior without it.

You can email me if you'd like to know more.

Rupert Sheldrake explains his wild theory on where memories could be are stored in this interview series with scientists ('A Glorious Accident'): https://youtu.be/RtofjlCkUno?t=2912

Or maybe it has something to do with bioelectricity as one of the researchers Mark Levin theorizes:


Ouch. Turns out even worms backup more frequently than humans do.

What's the possibility these worms have some off-body cloud like memory storage!

You haven't heard about the controversial theories of morphogenetic fields and morphic resonance? Rupert Sheldrake explains his idea on where memory is stored: https://youtu.be/RtofjlCkUno?t=2912

very interesting, no I have not heard about this theory before.

Worms have very few neurons though. Someone simulated one with a toy robot and it acted very much like an earthworm.

There is the http://openworm.org/ project that tries to simulate a simple worm. It's not as easy as one might think, even if the whole connectome of the worm is known.

There is also the "person lives normal life, found to have almost no brain" phenomenon:


Worms don't really have a head though. One end is a mouth, the other is an anus. Their neural function happen within the handful of neurons they have in-between. There is little wonder that the memories in these neurons are kept.

I've read that with ECM (extracellular matrix) we can regenerate fingers, but more complex organs are possibly out of question.

"Then the team showed the worms with the regrown heads where to find food, essentially a refresher course of their light training before decapitation."


Could be the regenerated heads learn faster because they are fresh, just like after a good night of sleep.

there's a good null control for that experiment which i presume they did.

Do they remember having their heads cut off?

Should add (2013) to title.

Interesting stuff though.

Has there been any further research or developments relating to this since then?

They need to make this happen for humans, it would revolutionize the cosmetics industry

I see what you did there ;-)

More evidence that memories are at least partially epigenetic.

Surprising but I guess it makes sense since we know of "muscle memory" as storing information outside of the brain.

Same with decapitated chickens who are clearly still experiencing panic and attempting to flee until they die.

I was always pretty sure "muscle memory" was a misnomer that actually referred to memory in the cerebellum. The headless chicken thing does put a damper on that theory, though.

Keep in mind that, while Mike (the chicken) did have most of his head cut off, some of his brain—and indeed most likely his cerebellum—was left intact.

"If the bird still has a bottom beak, the cerebellum and brain stem are likely still intact, which makes the chicken’s basic motor functions and ability to breathe quite likely." - Dr. Wayne J. Kuenzel (a poultry physiologist and neurobiologist) [1]

[1] https://modernfarmer.com/2014/08/heres-chicken-can-live-with...

"Muscle memory is stored outside of the brain" -- reference?

Decapitated chickens could be entirely driven by processes already communicated just before decapitation. This claims to be much more.

(In mammals) neurons lace the gut and other organs, and are implicated both in cognition and recall. For example Damasio's Somatic Marker Hypothesis holds that affective decision making 'polls' physiological responses which direct affect, providing intuitive 'system 1' information to aid decision making.

There's a whole field of embodied cognition which studies the interaction of the body and brain / central nervous system in behaviour and decision making.

While all this is a far cry from regenerating memories in the sense we think of them; the authors are merely referring to conditioned information, which could certainly be stored in the extra-cortical nervous system.

What’s the relation to “muscle memory”?

Could it be some extreme form of muscle-memory ?

That's even better regeneration than Wolverine

Rather a side point but I've always been bemused by how people refer to decapitation.

"Decapitated body" makes sense. But we mostly consider the head when talking about people (mugshots are heads, etc) -- so why aren't people decorporated rather than decapitated? Lavoisier's blinking experiment after his beheading didn't involve picking up his body!

(yes, yes I know that that is why this planaria experiment is so interesting).

If you don't know about Lavoisier's alleged extreme science experiment: http://www.strangehistory.net/2011/02/06/lavoisier-blinks/

People are decapitated, because they're the direct object of "decapitation" – the verb describing the removal of the head from the body.

I disagree that "we mostly consider the head when talking about people". We might mostly consider the face when talking about identity, but what specifically we consider in a person is context-dependent.

Also, "decorporation" would indeed suggest the removal of the body – but from what? "Decapitation" makes sense because the head is a part of the body. "Decorporation" would require the body to be removed from a larger whole, if it's to follow the same latinate prefix pattern.

Indeed, to remove the body from the important part — the head.

Likewise a “head transplant” always seems like a weird thing to discuss. It’s really (from my PoV) a “body transplant.” Unless you’d be happy receiving a head transplant from me :-)

OK, I reconsidered slightly my response to you (but can’t edit any more). The construct “a decapitated body” doesn’t sound odd to me, but “He was decapitated” does sound odd.

The head is the larger whole just not physically. Conceptually.

Historically the soul was seen sitting in the heart or the diaphragm, the chest basically, as far as I know. Because the torso exhibits features looking like a face (nipples as eyes and so on) which works to scare animals, at least. Therefore, as far as there is a concept, its should be stronly tied to the torso, from a developmental perspective. Decapitation is a rather archaic practice, anyway.

Regarding Lavoisier, "alleged" is correct. There seems to be no historical evidence that Lavoisier was the subject of this experiment, though it does make for a good story and was probably tried by someone at some point. See http://msgboard.snopes.com/cgi-bin/ultimatebb.cgi?ubb=get_to...

Makes you wonder what kind of secret research is going on in China where the communist Govt has fewer "ethical concerns". A Chinese doctor friend of mine mentioned that Chinese no longer much care for Western research. I don't know if this was an exaggeration but interesting to know

The title is misleading. I did a science project on this in the early 1990s. The paper mentions that the retention of memories after decapitation has been known since the 1950s. The news here seems to be that they have developed a computerized system to allow for easier, more consistent study of this phenomenon. This reminds me of Feynman's Cargo Cult of Science essay where he talks about the research that went into how to research rats, and why that was good science that many others ignored.

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