From the archive: Of molecules and memories
Many Minds
Hi friends! We're taking a much-needed August pause—we'll have new episodes for you in September. In the meanwhile, enjoy this pick from our archives! _____ [originally aired February 8, 2024] Where do memories live in the brain? If you've ever taken a neuroscience class, you probably learned that they're stored in our synapses, in the connections between our neurons. The basic idea is that, whenever we have an experience, the neurons involved fire together in time, and the synaptic connections between them get stronger. In this way, our memories for those experiences become minutely etched...
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From the archive: Consider the spider
Many Minds
Hi friends! We're taking a much-needed August pause—we'll have new episodes for you in September. In the meanwhile, enjoy this pick from our archives! _____ [originally aired May 30, 2024] Maybe your idea of spiders is a bit like mine was. You probably know that they have eight legs, that some are hairy. Perhaps you imagine them spending most of their time sitting in their webs—those classic-looking ones, of course—waiting for snacks to arrive. Maybe you consider them vaguely menacing, or even dangerous. Now this is not all completely inaccurate—spiders do have eight legs, after...
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The shaman with a thousand faces
Many Minds
When you hear the word "shaman," I'm guessing a web of associations starts to form in your mind. Perhaps you imagine strange ceremonies and strong substances; maybe you think of an earlier time when magic and superstition reigned. But shamanism is not just some relic of the past, or a curio from exotic lands. It's part of our present, and it will almost certainly be part of our future. This is because the roots of shamanism lie within us all. My guest today is . Manvir is an Assistant Professor of Anthropology at the University of California, Davis and to The New Yorker. He's also the author...
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Varieties of childhood
Many Minds
Childhood is a special time, a strange time. Children are adored and catered to—they're given their own menus and bedrooms. They're considered delicate and precious, and so we cushion them from every imaginable risk. Kids are encouraged to play, of course—but very often it's under the watchful eye of anxious adults. This, anyway, is how childhood looks in much of the United States today. But is this the way childhood looks everywhere? Is this the way human childhoods have always been? My guests today are and . Dorsa is an Assistant Professor of Psychology & Neuroscience at Duke...
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Science, AI, and illusions of understanding
Many Minds
AI will fundamentally transform science. It will supercharge the research process, making it faster and more efficient and broader in scope. It will make scientists themselves vastly more productive, more objective, maybe more creative. It will make many human participants—and probably some human scientists—obsolete… Or at least these are some of the claims we are hearing these days. There is no question that various AI tools could radically reshape how science is done, and how much science is done. What we stand to gain in all this is pretty clear. What we stand to lose is less obvious,...
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The primeval soil of play
Many Minds
Puppies wrestling and mock-biting each other. Toddlers playing hide and seek. Kittens pouncing—repeatedly—on a toy mouse. You've no doubt looked on at scenes like this with amusement. And you've no doubt seen some of those viral videos—of ravens sledding down hills, of bumble bees playing with balls. All these moments make us smile, maybe even giggle. But the scientific questions they raise merit serious attention. Where do we see play in the animal kingdom? Where do we not? What functions does play serve? Do we—and many other creatures—have an elemental need for play? My guest today...
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The big five and beyond
Many Minds
If you've heard anything about the study of human personality, you've probably heard about the “big five.” This is a framework that attempts to characterize human personality in terms of five broad factors or dimensions—neuroticism, extraversion, openness, conscientiousness, and agreeableness. The big five framework has been enormously influential, generating heaps and heaps of data, and study after study on the stability of personality, on the factors that shape our personalities, on how our personalities predict success and satisfaction. But is the big five really the best we can do?...
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Philosophers on psychedelics
Many Minds
Some call it the "psychedelic renaissance." In the last decade or so, interest in psychedelic drugs has surged—and not just among Silicon Valley types and psychiatrists and neuroscientists. It's also surged among a stereotypically soberer crowd: academic philosophers. The reasons are clear. With their varied and sometimes transformative effects, psychedelics raise ethical questions, epistemological questions, metaphysical questions, questions about the nature of experience and the nature of the mind. My guest today is . Chris is a philosopher of cognitive science at the University of Western...
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The cuttlefish and its coat of many colors
Many Minds
We humans have a hard time becoming invisible. For better or worse, we're basically stuck with the skin and body we have; we’re pretty fixed in our color, our shape, our overall appearance. And so we're fascinated by creatures that aren't—creatures that morph to meet the moment, that can functionally disappear, that can shape-shift on a dime. And no creatures are more skilled, more astonishing, more bedazzling in their abilities to do this kind of thing than the cephalopods. But how do they do this exactly? What's going on in their skin? What's going on under their skin? And what's going...
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Life, free energy, and the pursuit of goals
Many Minds
You've probably come across the "free energy principle." It's become one of the most influential ideas in the broader cognitive sciences. Since the neuroscientist Karl Friston first introduced it in 2005, the theory has been fleshed out, extended, generalized, criticized, and cited thousands and thousands of times. But what is this idea, exactly? What does it say about the nature of brains and minds? What does it say about the phenomenon of life itself? And is anything that it says really that new? My guest today is . Kate is a philosopher at the University of Edinburgh and the author of the...
info_outlineHi friends!
We're taking a much-needed August pause—we'll have new episodes for you in September. In the meanwhile, enjoy this pick from our archives!
_____
[originally aired February 8, 2024]
Where do memories live in the brain? If you've ever taken a neuroscience class, you probably learned that they're stored in our synapses, in the connections between our neurons. The basic idea is that, whenever we have an experience, the neurons involved fire together in time, and the synaptic connections between them get stronger. In this way, our memories for those experiences become minutely etched into our brains. This is what might be called the synaptic view of memory—it's the story you'll find in textbooks, and it's often treated as settled fact. But some reject this account entirely. The real storehouses of memory, they argue, lie elsewhere.
My guest today is Dr. Sam Gershman. Sam is Professor of Psychology at Harvard University, and the director of the Computational Cognitive Neuroscience Lab there. In a recent paper, he marshals a wide-ranging critique of the synaptic view. He makes a compelling case that synapses can't be the whole story—that we also have to look inside the neurons themselves.
Here, Sam and I first discuss the synaptic view and the evidence that seems to support it. We then talk about some of the problems with this classic picture. We consider, for example, cases where memories survive the radical destruction of synapses; and, more provocatively, cases where memories are formed in single-celled organisms that lack synapses altogether. We talk about the dissenting view, long lurking in the margins, that intracellular molecules like RNA could be the real storage sites of memory. Finally, we talk about Sam's new account—a synthesis that posits a role for both synapses and molecules. Along the way we touch on planaria and paramecia; spike-timing dependent plasticity; the patient H.M.; metamorphosis, hibernation, and memory transfer; the pioneering work of Beatrice Gelber; unfairly maligned ideas; and much, much more.
Before we get to it, one important announcement: Applications are now open for the 2024 Diverse Intelligences Summer Institute (or DISI)! The event will be held in beautiful, seaside St Andrews, Scotland, from June 30 to July 20. If you like this show—if you like the conversations we have and the questions we ask—it's a safe bet that you'd like DISI. You can find more info at disi.org—that's disi.org. Review of applications will begin on Mar 1, so don't delay.
Alright friends, on to my conversation about the biological basis of memory with Dr. Sam Gershman. Enjoy!
Notes and links
4:00 - A general audience article on planarian memory transfer experiments and the scientist who conducted them, James V. McConnell.
8:00 - For more on Dr. Gershman’s research and general approach, see his recent book and the publications on his lab website.
9:30 - A brief video explaining long-term potentiation. An overview of “Hebbian Learning.” The phrase “neurons that fire together wire together” was, contrary to widespread misattribution, coined by Dr. Carla Shatz here.
12:30 - The webpage of Dr. Jeremy Gunawardena, Associate Professor of Systems Biology at Harvard University. A recent paper from Dr. Gunawardena’s lab on the avoidance behaviors exhibited by the single-celled organism Stentor (which vindicates some disputed, century-old findings).
14:00 - A recent paper by C. R. Gallistel describing some of his views on the biological basis of memory.
19:00 - The term “engram” refers to the physical trace of a memory. See recent reviews about the so-called search for the engram here, here, and here.
20:00 - An article on the importance of H.M. in neuroscience.
28:00 - A review about the phenomenon of spike-timing dependent plasticity.
33:00 - An article, co-authored by former guest Dr. Michael Levin, on the evidence for memory persistence despite radical remodeling of brain structures. See our episode with Dr. Levin here.
35:00 - A study reporting the persistence of memories in decapitated planarians. A popular article about these findings.
36:30 - An article reviewing one chapter in the memory transfer history. Another article reviewing evidence for “vertical” memory transfer (between generations).
39:00 - For more recent demonstrations of memory transfer, see here and here.
40:00 - A paper by Dr. Gershman, Dr. Gunawardena, and colleagues reconsidering the evidence for learning in single cells and describing the contributions of Dr. Beatrice Gelber. A general audience article about Gelber following the publication of the paper by Dr. Gershman and colleagues.
45:00 – A recent article arguing for the need to understand computation in single-celled organisms to understand how computation evolved more generally.
46:30 – Another study of classical conditioning in paramecia, led by Dr. Todd Hennessey.
49:00 – For more on plant signaling, see our recent episode with Dr. Paco Calvo and Dr. Natalie Lawrence.
56:00 – A recent article on “serial reversal learning” and its neuroscientific basis.
1:07:00 – A 2010 paper demonstrating a role for methylation in memory.
Recommendations
The Behavior of the Lower Organisms, by Herbert Spencer Jennings
Memory and the Computational Brain, by C. R. Gallistel and Adam Philip King
Wetware, by Dennis Bray
Many Minds is a project of the Diverse Intelligences Summer Institute, which is made possible by a generous grant from the John Templeton Foundation to Indiana University. The show is hosted and produced by Kensy Cooperrider, with help from Assistant Producer Urte Laukaityte and with creative support from DISI Directors Erica Cartmill and Jacob Foster. Our artwork is by Ben Oldroyd. Our transcripts are created by Sarah Dopierala.
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