From the Vault: Devourer of Memories, Part 2

Stuff Work. Hey, welcome to Stuff to Blow Your Mind. My name is Robert Lamb and I'm Joe McCormick. And we're back with part two of our exploration of planarians, memory learning and conditioning. And of course today we're going to get to the cannibalism. That's right. If you did not listen to part one, do go back and listen to it, because we lay the groundwork. We discussed these or isms, why they're interesting. We discussed their regenerative powers.

We talk about McConnell himself. We talk about his personal and professional history as well as his run in with the unit Bomber. Right, uh, So that figure, of course is James V. McConnell, the American psychologist. But if you listen to the last episode, as you should before this one, you already know that. So we're picking up after McConnell's initial research demonstrating in the nineteen fifties that despite conventional wisdom that invertebrates could not learn, could not be trained

through classical conditioning or any other kind of associate of learning. Uh, McConnell and colleagues did in fact demonstrate that that's not true, at least for planarians, these flatworms, that that could be trained to react to something like a light stimulus. And we also discussed how it's just generally known to be true today that invertebrates can learn. The conventional wisdom at the time was wrong. But so to pick up with

McConnell's career. After completing his graduate degree at the University of Texas, I almost said Jerry O'Connell, not Jerry O'Connell. James McConnell moved on to the University of Michigan, where he continued his research into flatworms with the team that came to be known as the Polenarian Research Group or PR g So another piece of context for this research is a sort of quest for the holy Grail within twentieth century psychology and neuroscience, and this was the hunt

for the elusive ingram. It was believed by many in the mid century that a researcher, that the first researcher to actually pinpoint something known as the ingram, would receive the Nobel Prize for their work. But what was the ingram? The short version is that the ingram was believed to be the fundamental physical unit of memory represented in the body. In order for an animal to learn an association between two things, that memory has to be accompanied by some

kind of physical change inside the body. But what is the fun no mimental unit of that change. Is it a structural change in the brain that can be located or is it something else? So the idea is that you would see the physical evidence of learning and then potentially like that is physical evidence that could be then manipulated. Of course, yeah, it's sort of like searching for the atom. What the atom is to matter, the ingram would be to memory. What is the fundamental unit that that physically

indicates in the body a memory has been formed? And of course one motivation for studying whether simpler organisms like worms and other invertebrates could in fact learn associations through classical conditioning was that this might help move along the search for the ingram. If a biological phenomenon seems too complex to understand in one organism, you know, if you can't find it in a rabbit, everything is just too complicated.

Maybe you can get a foothold to understanding by looking for analogous phenomena in simpler organisms and then build your way back up. And it's a sensible way to go about it, of course. Uh So research in the middle of the twentieth century tried to locate the ingram two changes in a specific part of the brain and a rat,

but these efforts failed. In fact, rat brain memory research he demonstrated that there was no one location or structure in which the fundamental unit of memory association was to be found. Instead, learning seemed to involve wide swaths of the rat cortex, and today we know that certain regions

of the brain are especially important for memories. For example, fear based conditioning, like if you condition somebody to respond to a stimulus through conditioning due to an electric shock, that this seems to strongly implicate the amygdala, not just fear actually, but other types of emotional memory as well.

I think while memory of spatial locations and physical maps seems especially to implicate the hippocampus, But memories for complex actions maybe finding your way around a maze, as was often tried with rats, will involve lots of different parts of the brain at so you can't point to the memory in one specific part of the brain. It's using the whole brain basically. In the nineteen fifties, this wasn't

yet clear. It was It was just clear that memory, contrary to the expectations of many psychologists, couldn't be located in one particular structure or single point physical change in the brain. And because of the failure of researchers to locate a structural ingram at a single point in the brain, some researchers began to turn to other explanations, and McConnell was one of them. McConnell wondered, what if memories were

not stored exclusively in structures in the brain. Could you have memories in your hands, in your blood, in your guts. Was there a deeper chemical rather than structural basis for our memories. And here's where the planarians again become an invaluable research tool in looking into could you have memories outside the brain? Could there be such a thing as a memory chemical or a memory molecule found throughout the body. And yeah, this we come back to the regenerative powers

of the planarian. We described this in the first episode as being something like The Sorcerer's Apprentice, the old Disney animation from Fantasia, in which the uh what what is it? It's a broom that is brought to life to do a particular task to carry water from a well, I think, and then yeah, it was it's a well. And then and then Nikki, the Sorcerer's Apprentice in this case, ends

up having to to destroy it. So he chops in into a million pieces with his axe, and then all those millions of pieces, each little sliver of the broom comes back to life and grows into a whole new, fresh, uh broom with that walks around on two legs and carries buckets of water. Right, And this connects to the regenerative powers of planaria, because if you cut a planarian in half, one of these flatworms just chop it in

half crosswise, separating the head from the tail. Each half of the worm would grow the part it lost, So the decapitated head could regrow a tail, and the decapitated

tail could regrow ahead, which means regrowing a brain. So McConnell's question was, if I condition a flat worm to learn something, maybe have a response to a stimulus like a flashing light, and then I cut it in half, which half of the worm will retain the response if either Now you might think the answer is obvious, right, Well, obviously the head half is where the brain is, so the head half will retain the conditioning if either side does,

and the tail half won't. Right that that seems like the obvious conclusion, right, Yeah, that's what you would assume. That's what like a basic understanding of monster movies would have you assumed. Yes, McConnell found this was not exactly true in his experiments on freshwater flat worms called dogs

a Dorado cephala. If you classically condition the worm to respond to a light and then you cut the flat worm into two halves, both halves retained the condition ng, and in a few cases the tail retained the conditioning more strongly than the head. So you could cut the head off, the tail would regrow ahead, and it would still respond like the way it had learned to respond when it had its original head. So if all the learning was in the brain, how could that be possible? Right?

This would seem to indicate that there's some sort of memory retention or memory storage going on within the body itself. Right, And these results were eventually published in the Journal of Comparative and Physiological Psychology. But then it gets even weirder because we're going to start playing flat worm Ship of Theseus? Uh So a refresher on the Ship of Theseus thought experiment, Robert, do you want to do the honors here? Oh? Sure?

This is the basic idea. If you you have this ship, for this legendary Ship of Theseus, you're celebrating it across the decades. Think about it. Is a ship that is docked for decades tends to fall apart piece by piece, so you replace it piece by piece. Eventually you reach the point where you have replaced every single piece of this vessel. The question is, is the Ship of Theseus any longer the Ship of Theseus? Is it? It's It's not physically the same ship it was before, but it

is the same shape. It's just all the pieces have been at this point replaced. Now, what if you in fact do this with flatworms since they can regenerate, And this is exactly what they tried in a series of experiments. McConnell and the Planarian Research Group showed that if you cut a word, like, for example, you cut a flat worm's head off after it's been conditioned and trained, so it has this memory response, and then that tail regrows ahead, and then you cut the original tail off, so the

regenerated head regrows a tail. Now you've got no original part of the worm left. So you've been through these multiple generations of cutting a worm apart and letting it regenerate, and yet their experiments found that some learning training memory was retained across the multiple generations where there was no original part of the worm left. Again, how would this

be possible? Like if memories are stored exclusively in the brain, how could a memory necessary to establish a conditioned response still operate within a tail that had its head cut off, or a segment of a worm grown from a segment of a worm grown from a segment of a worm that had been through the conditioning, and this led McConnell to suppose that he had evidence that memory may have strong chemical components. They're not limited to activity within the brain.

There could be actual molecules of chemical memory coursing through the worm's body. Now, if this were true, this would of course be a revolutionary discovery, right right right, because of course it would conceivably apply to other organisms. I mean, that's that's the thing. It might force us to completely rethink what we thought we knew about memory, right And of course if it were true of flat worms, as possible, it would only be true of flat worms. But yeah,

you don't know where else this would lead. Could it even be true of more complex animals. So it was this line of research about cut up flatworms retaining memories that led actually to the founding of the magazine we talked about in the last episode, The Worm Runners Digest. This was McConnell's magazine that quite strangely combined both real research on on planarians. It was like real flatworm research published alongside weird poems and joke articles and satirical articles

and stuff. It's such a weird title. The worm part clearly relates to the worm experiments. But it also brings to mind like blade Runner, except it's worm runner. And it also makes me think of various Gary Larson far Side cartoons which a worm is perhaps, you know, wearing

sweatpants and linn running. That's good, But the joke and title in the title is actually a reference to like common terms used by psychologists of this period, lots of research about learning and memory involved rats and mazes, and oh, researchers who did this kind of work referred to themselves jokingly in the nineteen fifties as rat runners. McConnell's variation is self explanatory. Jerry the worm Runner, not Jerry Jr. Jerry O'Connell, James JF there James the worm Runner then,

but yeah, actually so coming back. So this led to the founding of this strange magazine that he became very well known for. Uh. The story has summarized by Larry Stern, and I mentioned several sources at the beginning of the last episode. We're still referring to those sources in this episode. One was an article by Larry Stern that that talked

about the founding of this magazine. So in nineteen fifty nine, McConnell presented some of this work uh this work about chopping up flat worms and then supposedly retaining memories to an annual convention of the American Psychological Association the a p A. And this included results collected by a member

of the planary in research group named Riva Jacobson. And again, this research showed that not only could a decapitated flatworm retain associate of learning, but essentially the ship of THESEUS flatworm containing no tissue of the original worm could also retain learning. And after the presentation, Newsweek published an article summarizing the research. This led to a huge surge of popular interest in McConnell's work, and so Larry Stern writes quote.

Shortly after the Newsweek coverage, McConnell was inundated with letters from high school students from around the country asking where they could obtain worms for their projects and how they should go about caring for and training them. Some students, according to McConnell, demanded that he sent them a few hundred trained worms at once, as their projects were due within days. It sounds a little familiar, right, Students don't do things like this, But McConnell did want to help

students conduct their own flatworm research. I get the feeling he was into this idea, but he realized very quickly that it didn't make sense to try to respond to each letter individually, so instead he decided to publish a manual on how to replicate the experiments performed by the PRG,

and he titled this document The Worm Runners Digest. However, after publishing this manual under that title, McConnell started getting submissions to appear in future issues, so he began publishing this so called journal on a regular basis, again, including both real research and psychological in jokes, cartoons, poems, and all that kind of stuff interesting, So it's kind of

accidentally became a continuing publication. Yeah. Now, as you can imagine, some people didn't take kindly to this mix of subject matter. In nineteen sixty four, after some readers complained that they couldn't tell the real research from the jokes and the satire, they started publishing the satirical elements upside down in the back half of the journal. So there was some attempt there to clear up the confusion. But I think for a lot of scientists, the pure proximity of the different

material was was a problem no matter how clear the division. Well, I think that's understandable. We talked before about the Ignoble Prizes, for instance, about most of the individuals involved and honored by these prizes that celebrate, you know, scientific studies that are legitimate scientific studies, but that are in on some level humorous or amusing. But you still have some individuals in the scientific world who do not see the value

of that. So if they're so, if feathers are ever ruffled by the Ignoble Prizes, obviously something like this would ruffle feathers as well. Yes, uh so. Then in nineteen sixty seven there came another split where the serious half of the journal was just formally cleaved and renamed in fact cloven and half like a flatworm, uh, chopped right off, decapitated. The serious half was renamed the Journal of Biological Psychology, and the worm runners Digest became the soul Haven of Humor,

and it continued publishing that way until all. Right, on that note, we're going to take a quick break, but we will be right back. Alright, We're back alright, So to jump back into the progression of James McConnell's research. We're we're brought back to this uestion of a non brain chemical basis for memory. Couldn't memory, or at least some memory, some types of memories be stored chemically rather than structurally dispersed in the body, in molecules. And here's

where we get to the cannibalism. So if there were in fact molecules within an animal representing some kind of chemical memory, such as memory of how to navigate a maze, could this be demonstrated? Could those molecules be shared from one animal to another? And this makes sense, that's what creatures do. They take molecules from each other, from other organisms and put them into themselves. Sure, we absorbed the

molecules existing in other organisms for nutrition. Uh so maybe you could molecules be absorbed from one organism to another four memory transfer. So the first method they tried, and this is based on the reporting of one of those Larry Stern articles. The first method they tried was to splice the head of a conditioned worm onto the tail of an unconditioned worm to see if it would share molecules, right to force them to exchange the alleged memory molecules,

but the transplant did not work. The head would not stay attached. Then they tried to liquefy fully conditioned flatworms and inject their juice into untrained worms, but this was also difficult. The planarians were too small to be injected basically, and sometimes they exploded when injected. In Larry Stern's words, quote, it was like trying to impale a prune with a javelin a lot of horrific things done to diplanarians in

these experiments. I guess they are a simple enough organisms that have to be so upset about them, I guess, But it's still one can't help but pause a little on some of these, right, some of the grinding, the sauce, the gravy, the flatworm sauce. So how do you get those hypothetical memory molecules in there? If you can't inject them, you can't transplant ahead on. So the next route they tried, and this in the year nineteen sixty was experimental planarian cannibalism.

This would be the old fashioned way of getting molecules from one organism into the other. Sure, so apparently the idea came from a flatworm researcher named Jay Boyd Best, who communicated to McConnell about the fact that one particular species of planarian was known for cannibalistic behavior. So here's

the answer. You train the worms to respond to to a maze or to the light, whatever the conditioning stimulus is, and then they learn the conditioning and then you grind them up into worm gravy, and then you feed the worm gravy to the untrained naive worms, and you see what happens. And astonishingly, their early experiments with this method looked very promising, including a number of early replication attempts with blinding procedures to remove the possibility of experiment or bias,

supposedly confirming their early results. So, if it were true that memory molecules are being exchanged through this strange cannibalistic ritual, could I, you know, with this extend to humans? Could could I drink your flesh and gain your memories? And how was it happening? What was the chemical basis here?

So one interesting line of reasoning here followed from the still somewhat recent discoveries about genetic information being stored in and mediated by nucleic acids DNA and RNA remember, you know, we're not too far from from the discovery of the double helix here. So, if DNA and RNA could be involved in an information management process passing genetic information across generations from parents to offspring, could the same molecules also in code and mediate other types of information? I mean

information is in the DNA. So specifically, could the information content of memories somehow be coded into DNA or RNA and then dispersed through the body, but also transferred from one body to another. And so this is the line

they took. A McConnell and his team conducted experiments and published results that seemed to back up the idea, at least for a while, that RNA played some important role in facilitating memory, and that RNA could be used to chemically inoculate naive worms with the memory associations of their more worldly predecessors. And again, just consider how revolutionary this would be If it turned out to be true. You'd be forced to wonder how far the principle could be taken.

What did this only apply to planarians or did it extend to other more complex animals. Would there be ways in which humans could undergo chemical learning? Could you train the mind in some way with an injection alone or even a pill. Even if it only worked for like broad associative learning such as you know, the kind of things you get through classical conditioning with an electric shock and a single stimulus, you could still possibly imagine profound benefits.

Just one idea comes to mind, like say you're struggling with a drug addiction. You could you seek out an injection of of memory molecules to establish a strong averse reaction to your drug of choice such that you wouldn't want to take it anymore. Yeah, Or to get into some of the behavioral his ideas that we discussed in the first episode, some of those ideas that that that

McConnell's very outspoken about it, even later in life. You could have some sort of a cocktail that could be injected into an individual that had a history of violence and history of of you know, breaking the law and rebelling against authority figures, and you could potentially fix them with this injection. Yeah. And of course there you get into the more nefarious possible thing, like you can probably instantaneously imagine so many horrible, insidious uses for injectable conditioning.

If such a thing were possible. Oh yes, I mean, as with any science, many many fabulous uses come to mind, but so many nightmares as well. But we should stop and be real for a second here. Even if these findings had turned out to be totally solid for plenaria and more on that in a moment, we should know better than to freely extrapolate from worms to humans. I think this is one of the most classic traps that people fall into and interpreting biological research. I'd say more

often as people extrapolating from like rats to humans. But this isn't a much larger jump. This isn't even a vertebrate animal. Yeah, I mean, you can't help. I often find that I can't help, but but at least think about that on some level when I read a science headline, I can't help it. Put myself into into it somehow and imagine myself as the creature, right, And it's often

I mean, it's just done right there in the press. Again, it's fine to wonder about what possibilities could be implied by studies in rats for humans, but you can't just you know, conclude from one to another. We can't help but anthropomorphize virtually any creature, and if that creatures in a study, we're also going to end up anthropomorphizing that as well. But James McConnell, true to form, as we know from the last episode, was not one to be

shy or cautious about interpreting his findings. He loudly proclaimed them to the public, advertising his results on TV programs. He apparently embraced the nickname mccannibal. Uh. And he predicted an era of memory pills like we just discussed. So you might be thinking, like, wait a minute, he should know better than to extrapolate from planarian even if you assumed the planarian research to be on solid uh. And

we'll introduce some caveats to that. But even if you did assume that, how could you jump from that to human memory pills? That seems like a you know, a leap of miles of assumptions. Yeah, very much. And it does seem from from what I was reading, especially in Rilling's paper about McConnell, that it seemed like to him he sort of had a sense of humor about talking about memory pills, like as if he were sort of

joking when he talked about memory pills. But that was not clear to the popular audience that was listening on the TV. You know, they weren't psychologists. They didn't understand that he was kind of kidding when he said that makes sense, so certainly. And then also they're going to be like a few different levels, so I could see like he may joke about it here in this paper or joke about it to this individual, but then you're gonna have different levels of coverage and it's going to

get out of out of control pretty quickly. Yes, so really writes that quote. McConnell's work on retention following regeneration and Planaria provides a case study in sensational journalism and illustrates how his media work escaped the normal mechanisms of

peer review. So the idea is that McConnell and colleagues would do an experiment, they would obtain a very strange and interesting result that looked solid enough to get published in an academic journal, and then McConnell would immediately want to engage in quote, wild sounding conjectures interpreting the meaning of his results and how they would be applied in the future. And scientific journals generally are like One example was the editor Harry harlow Uh generally refused to publish

these wild interpretive or speculative addendums to the research. They just say, well, we'll publish your study, but you've got to cut out this section about memory pills that doesn't belong in here. But of course there's no peer review

in the popular media. So he could go on TV and say memory pills as much as he wanted, and it turned out that that kind of thing on TV gets you booked on TV again because it's exciting, right, I mean, that's like something that people can picture, it's not hard to understand, and it's it's very like what revolutionary. That's what you want in a science segment on your

your news programs. You want something relatable, and here's this guy that is making it relatable and exciting with promises that are not at all implied by the research being discussed. Even if the research itself is a solid and retrospectively that maybe in doubt. So just one example, in nineteen fifty nine, an article in Newsweek covering McConnell and the PRG research claimed it may be that in schools of future students will facilitate the ability to retain information with

chemical injections. Apparently, there was also a lot of misunderstanding in the media, misunderstanding the fact that multiple generations of regenerated planaria could retain training, and they misunderstood this is the fact that memories can be inherited in apparent to child sense, which led to all kinds of Lamarckian interpretation. So I think there there's all. There was also just confusion stemming from the use of the word inherited and generations.

He was talking about like generations being chopped up and regenerating, which is quite different than what we understand, right, and again he's coming down he's talking about memories here. There are other things that you know, there's certainly things that affect that have generational effects in biology and in human biology. I think we've talked about studies before and about body size following periods of starvation, that sort of thing. But

but again we're talking about memories here. He is explicitly talking about memory. Yes, And and the one that that was quoted in Rilling was regarding cannibalistic memory transfer, the one where you eat the worm gravy and you gain

that worm's memories. Supposedly, there was a nineteen sixty four article in the Saturday Evening Post that claimed we quote might someday enable us or it might someday enable us to learn the piano by taking a pill, or to take calculus by injection, which at that point is is very crude, gross, kind of like over interpretation of what the memories here are and the you know, the leap from one organism to another, you just like do a

line of ground up Beethoven. Yeah, I mean, this is this is so outrageous that, like I I feel like I would I would feel like I was over stretching to use this as an outrageous example of a possibility, you know, like earlier I I did the the far future example of criminals being treated like this seems even this is even seems crazier, but on the same hand also attractive the idea of being able to, uh, say,

master calculus by simply in acting something into your body. Yeah, though I hope also our questions about potential applications if this were true were heavily caveat, so in the mid nineteen sixties there were even studies following up on this, cannibalism research claiming to bear out chemical memory transferring other species, such as in rats. Again, that's kind of hard to believe. And so like. For a few years there in the sixties,

things looked incredibly promising with this research. But fortunately or unfortunately, depending on how you look at it, it was not to last. There was a problem with the p RGS cannibalistic memory transfer research, and it was just that it didn't hold up to sustained scrutiny over time. Over time properly blinded and controlled efforts to replicate McConnell's results, a few of them came in saying yeah, we replicated, but a lot did not produce the same effects for cannibalism

or other chemical methods of memory transfer. According to Rilling in nineteen seventy one, I guess this would be as a result of some of these failures, the Planary in Research group lost its grand support and this led McConnell to change focus. And after this in the seventies he went on to write a very influential and from what I can tell, mostly well regarded textbook for introductory psychology. Apparently, one thing that set it apart in the field was

that it used a lot of fiction. It introduced students to psychological research methods with the use of stories and like fictional framing narratives to explain the principles that were discussed in each chapter, even including one chapter about memory, it seems to begin with a fictionalized version of the story of his research with Thompson in nineteen fifty four five or so, uh, though incorporating lessons about control groups that he had not learned very well back then, and

as we discussed more in the previous episode. Later in his career, I think he was known more maybe for being a fierce public advocate of the powers of behavior modification through conditioning. Again, this was an era in which behaviorist psychology was seen by many as a potentially revolutionary scientific tool for minute control of human minds and lives.

This is the birth of the modern concept of brainwashing, right, and McConnell wrote and appeared on TV arguing the behavioral conditioning would fundamentally alter the nature of criminal justice in democratic society itself. I think there was one article he wrote that was titled something like we must brainwash criminals. Now, well, that's a great headline though, no doubt about it. Yeah, certainly,

if you want to get the clicks. Uh, yeah, he was maybe he maybe he was clickbait before the internet. He does, he does seem very clickbaity. And this is something some of his colleagues said about them. Is quoted in the Rilling paper that he wanted to shock people. He wanted to say things that would make people say, what, what's this guy talking about? That can't be true? And he said, you know, the idea was you you bring people in by shocking them, and then you educate them

with the science. And you know, I guess that can be an okay method if what you if what you say in order to shock people isn't fund mentally dishonest in some way, right, Yeah, I mean it's it's kind of it kind of gets into a similar of like leading with an example, you know, and sometimes it's an

outrageous example. Sometimes, like on this show, we we bring up a monster, something fantastic, and we use that to talk about something that is that is real and talk about actual scientific studies or actual biology that someone matches up to that. But well, I hope we never do. I hope if we start with god Zilla, we don't leave you with the impression at the end of the episode,

that Godzilla is real and true. Right, Yeah, But it is interesting how it seems like some of the things that did make him such a great communicator and ultimately like a great author of an introductory psychology book. Uh, those are also some of the things that got him in trouble. Yeah, that totally seems to be true based

on everything I've read. But but coming back to the memory transfer issue, I just want to say that I think the conclusion, unfortunately at the end, is that the cannibalistic memory transfer saga is widely regarded now as a dead end. Despite a few reports of moderate replication successes, McConnell's results ultimately did not hold up to widespread scrutiny

and the rigorous application of controls by others. And it looks like his supposed discoveries about memory transfer through injection or cannibalism were probably wrong, but not all of his

conclusions were necessarily wrong. I mean again, one of the points of Rilling's article seems to be that despite the ultimate failure of the memory transfer through cannibalism theory, McConnell did make truly important contributions to research on invertebrate learning in the nineteen fifties, and while the memory transfer, the memory molecule transfer through cannibalism is almost definitely a dead end, more recent studies have sort of raised the question of

whether his like decapitation and transplantation research might have been on the right track. All Right, we're gonna take one more break. When we come back, we're going to discuss some of these modern follow ups regarding planarian decapitation and

brain transplant. Alright, we're back. So we discussed through through the end of the career of of James V. McConnell, who studied planarians memory memory transfer, or memories outside of the brain, and we we brought up the idea that this subject has been revisited by researchers just in the past few years who think that while McConnell was probably wrong about, like say, eating flat worms and gaining their memories, there may be some truth to the idea of memories

somehow being stored outside the brain or transferred without a full brain. Yeah. So, for instance, it has been demonstrated that if you transplant the planarian's brain into another worm's body, uh, it will result in at least partial recovery or of function, even if the brain is put in backwards or transplanted

across species. Uh. The author Pagan, who we brought up earlier, who wrote the first brain uh, he points this out, points out that basically the cross species transplants held meaning there was no rejection, and forty eight hours later the worm retained mostly normal behavior. I mean, that's pretty weird, but again it's worms. Like Yeah. One of the big take comes from all of this is that planarian brains

and polinarian in general are strange. Right, So a lot of what we determine what a lot of what we learned from this research you could interpret as some fascinating deeper insight about biology as a whole, or you could

interpret it as fascinating specific facts about these flatworms. Absolutely h So in particular, though, the gun and there are referring to a study by Davies at all, and they were working with a species of planarian that actually can't regenerate brain tissue, but a transplanted brain will take root and quote nerves exiting the brain tended to join with the peripheral nerves closest to them, which I think is a hederful image of the brain being implanted in this

creature and then like the like the like roots forming, like the vein connects itself, it hooks itself up like a car battery that has been placed in the inside another via a new vehicle, and all the things just kind of hook up automatically, plug and play. Yeah. Well, or like like mistletoe or some other kind of parasite that like sticks, it's little, it's how stori um or whatever, the little spikes down into the host. Yeah, it's it's

it's weird. It's definitely not the human experience. I mean not to not to discuss, you know, the whole body transplant or human brain and head transplant much in this episode, but basically it's very complicated, if not impossible in humans. Yeah. Well, and again to look at memory more broadly, neuroscientists today

mostly broadly understand memories to be neural networks, right. Networks within the brains are strings of reinforced connections between neurons and brain regions that specified memories by their cross linked structure. A memory is in some way a series of connections between neurons and the brain. Uh. Though that does seem

to be the case. Beyond that broad picture, there's still a lot we don't know about the physical basis of memory, and so even in especially in organisms like flatworms, there are ways in which memory could be operating and that are still mysterious to us right now. Of course, the

quest to solve these mysteries continues. A great deal of planarian research is still going on, and you see quite a bit of it come out of Tufts University, and you'll see UM a researcher by the name of Michael Levin often is a is a head author or co

author or contributing author on these papers. Yeah, and there was one big study that got some press being connected back to McConnell's research that Levin was at least one of the authors on UM and and basically it had to do with replicating a version of the decapitation experiment showing that somehow it appeared memory if the study was designed properly and there wasn't some kind of flaw that people didn't notice in there, that memories maybe were somehow

being transferred through the decapitation process. Right This is a two thousand thirteen Tough University study that found that a decapitated flat worm that grows a new head keeps its old memories. Uh. For instance, the serahs sing article about this, it appeared in Nautilus, carried the title decapitation but not cannibalism. Might transmit memories without context. That's a pretty weird title, right, But then within context of the article refers back to

McConnell's work quite a bit. And the idea here is that some trace of the of memory might be stored in neural circuits outside the brain. And certainly when you take that and you compare it to these you know, these other into this previous study. Uh, with with one brain being dropped into a new creature, a new a new individual and seeing it to you know, take root and uh and seemingly bounced back. Uh, that becomes all

the more interesting. Yeah. One of the things that has clearly been the case, and this was discussed in that article in the Verge we talked about in the last episode, is that Levin's research has been focused on trying to eliminate some of the problems that could have existed in the original McConnell research. One example is that that he helped to create um and a thing called an automatic

training apparatus. Basically, it's a robot for conditioning the flatworms to take the human element element out of the training process, to eliminate any kind of bias or error that could be introduced that way. But I love the idea in general of a robot for training worms. So that that two thousand thirteen study especially generated quite a bit of interest, and at the time there was there was mixed response

from the scientific community. Now, I do want to drive home that it is not my interpretation that Michael Levan

is anything like a McConnell figure. He seems he seems to be a very suspected researcher, and most of his work, like I said, he's seeing on a lot of studies for this general planaria research right now, I mean I don't I haven't seen anything where Michael Levin is going on TV and saying memory pills right right, uh and and and by and large it seems like most of his work just deals with with regeneration, uh in these

planaria worms. But yeah, so you had plenty of people that that were supportive and thought that, you know, they might be onto something. Others were a little critical at the time. Robert Kintridge, as a it was a psychologist at Durham University, and he pointed out in a two fifteen Verge article that Verge article we cited earlier that it might be simply related to quote behavior induced by a stress hormone itself triggered by the the textualized petrie

dishes unquote. And to clarify, they're part of what the study looked at to see conditioning in the flatworms was you'd have these textured petrie dishes where they would be swimming around the food they were gonna eat, and how fast they approached the food in a newly textured petrie dish environment was taken as a signal of their memory

or familiarity with the environment. Like you put a new flatworm and a textured petrie dish its circles for a while before going for the food because it's exploring its environment. It doesn't know. But after it's been trained with the texture and a petrie dish, it goes straight for the food because it already knows the environment. Right. Yeah. So so basically a number of individuals said, well, there there are aspects of the study that could have been better designed. Sure.

Now again, Michael Levin his research continues, he and you you'll find a number of studies from very recently that he's been involved with. He was an author on a study earlier this year neural control of body plan access in regenerating planaria. And in two thousand fifteen he put out a paper on the planarian regeneration model is deciphered by artificial intelligence and uh that same year he was also a co author on another study, uh that included

the growth of extra heads. Yeah. I've seen also that I think, both within and outside of planaria has just generally studied regeneration. Yeah. And with the pouplinaria, of course, it's it's just such an amazingly regenerative creature. You get things like like this. Uh. The second study that I mentioned from they were able to induce one species of flat worm to grow heads and brains characteristic of another species of flat worm without altering genomic sequence, and then

the individual later regenerated to the appropriate head shape. Huh. Now quickly, I guess one thing worth discussing is if the research associated with with Michael Levin is in fact correct, the results are valid, there's not some kind of flaw we're missing in the design of the study. And uh, and this is really going on the memories are surviving the regeneration without an original brain. How would you interpret this, Like, what does it mean if this is in fact true?

Uh So, a couple of ideas are given in the Verge article. Leven Hy Quote hypothesizes that memories could spread beyond the brain thanks to electrical charges generated by cells and the rest of the body. So there's some kind of information encoding that's just like coming from cells in the other body that are electrically stimulating something like a

memory response. But then there's another thing cited in the same piece by Ava Jablanca, a developmental biologist at Tel Aviv University, and she offers a speculative explanation involving particles called quote small r n a s, which are short copies of DNA, but they don't turn into proteins. They

don't generate proteins. So when a flatworm learns an association or an episode, something in this model about the brain chemistry would change, and then these changes alter the small RNA's present in the body, which of course are not confined to the brain because they migrate around between cells.

And by migrating around between cells, she says, perhaps they end up in stem cells that remain in the body after the worm's head is cut off, and to read from the article quote, when the worm's head grows back, the small rnais migrate back to the head, changing the brain's chemistry and allowing it to learn certain behaviors more quickly. Um. If true, the memory that Levin thinks is stored outside

the brain wouldn't be memory at all. Rather, the small RNAs would allow the flatworm to recover a brain environment that helps them learn a specific behavior more quickly. So the idea there is that if this speculative idea is correct, and again she she's very clear to stay this, this isn't something we know. Is just a speculative interpretation. Maybe

it works this way. Then what would be happening is these little chemical molecules don't transmit the memory prepare the new brain to learn a memory that was previously learned more quickly. Okay, so at least we have a hypothetical model of how this would actually work, which or at least here's one model presented anyway, Sure, but ultimately we don't know for sure. And again, another thing that we don't know for sure is if these results do hold up.

Is this something that's specific to planaria. Is it flatworms only that can transfer memories in this way, or could this be more applicable beyond flatworms to other organisms, because that's the thing. Other organisms can't regenerate like a like

a planaria can. But at the same time, we one of the one of the things that's often cited for research and clanaria regeneration is that we might learn something that could be appliable to humans, of course, especially and we're not even getting into memory implantation, just the idea that they have such impressive neural regenerative powers, the ability

to regenerate like damaged brain cells. You know, if we can, if we could develop some better method of doing that based on our studies of these organisms, then that would be tremendous. Of course. I mean though it when you introduce the idea of brain regeneration or anything like that to a human context, things emerge that don't necessarily seem

to be of concern when you're talking about planaria. Planaria don't seem to have extremely distinct personalities, uh, you know humans, do you know, however much we want to joke about humans acting like sheep and all being the same we you know, we we've got a lot of different stuff

going on in our heads. If you cut your head off and regrw it, what indication would you have that the new head would be you in any sense other than sharing your d n A. Well, I guess as long as it's said all the right things and I mean just go along just fine, it would be like a psmbie perhaps, Well, I mean, would it? I guess it would be a question of whether it would retain

any memories from your life. You could you talk about whether that might be stored in the body somehow, or even if you assume it, okay, it retains no memories whatsoever because those are just stored in the brain. Whatever may or may not be happening in flatworms doesn't happen in all at all in humans. Even if you assume all that, you'd also have to ask, like, what it's per senality be the same as your as personality is

so shaped by life experience. I don't know. It makes me wonder has anyone ever considered creating as like a science fiction yarn in which you look at what would human society be like if we had regenerative properties like this, like, what would war be like? What would uh what would reproduction and society be like? I mean, granted, I think the obvious answer, it would absolutely change everything. But the fun thing about science fiction is you don't you don't

have to go all the way. You can just sort of like tweak it, Like, what would this if we if I were to look at this particular vision for a totally regenerative clinary in human species, then what could I perhaps unravel about our actual human condition? Well? I mean I think we pretty much all at some state, at some point or other, get into a get into a place where not very happy with our own brain. We don't like the emotional patterns were feeling. Maybe we're

ruminating in bad ways. I mean, this happens pretty often to people. So what if you had the option to you get into a bad state like that, you know, you can just cut your head off and grow a new one. These are exactly what the horrifying orange creatures in Labyrinth they're all about when they come up to Sarah and they encourage your Hey, take your own head off, throw it around, try on a different head, Let your head try it out, try itself out on a different body.

See how it shakes out. Just you know, have to have a little fun. You're not a flat worm. Don't try it people, All right, We're gonna go ahead and close this out then, but we hope that you have enjoyed and then learned from this exploration. Perhaps you'll think of flat worms in a new light now, and perhaps you will even second guest memory a little bit as well. In the meantime, if you want to check out other episodes of Stuff to Blow your Mind, you'll find them

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