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
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.
You're still thinking in binary there. If a wave eroded a few atoms from the hull it's now the tiniest bit a new ship. If you round it to the nearest binary result you'd end up with "It's not a new ship".
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.
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.
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.
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..
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.
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.
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.
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:
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
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.
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.
"Then the team showed the worms with the regrown heads where to find food, essentially a refresher course of their light training before decapitation."
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]
(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.
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).
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.
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.
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.