Citation: Tal Shomrat, Michael Levin. Journal of Experimental Biology 2013. Published July 2, 2013
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.
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
...each piece has the ability to regenerate into a fully formed individual.
Reminds me of the famous https://en.wikipedia.org/wiki/Lernaean_Hydra
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.
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.
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 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."
My guess: barely long enough to die from dehydration.
"Brain Cells Share Information with Virus-Like Capsules"
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.
Would the worms remember without this “refresher course”?
So, no. But they do better with the refresher course than other worms if I understand correctly.
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.
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.
Or maybe it has something to do with bioelectricity as one of the researchers Mark Levin theorizes:
Interesting stuff though.
Has there been any further research or developments relating to this since then?
Same with decapitated chickens who are clearly still experiencing panic and attempting to flee until they die.
"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) 
Decapitated chickens could be entirely driven by processes already communicated just before decapitation. This claims to be much more.
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.
"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/
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.
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 :-)