Dr. Michael Kilgard on Huberman Lab: How to Rewire Brains

1. 0:00 – 3:24

   Michael Kilgard

   1. AHAndrew Huberman0:00

      Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Michael Kilgard. Dr. Michael Kilgard is a professor at the University of Texas at Dallas, and he is one of the world's leading experts in neuroplasticity, which is the brain's ability to change in response to experience. Since the beginning of the field of neuroscience, meaning for well over 100 years, it was understood that the young brain can change. Kids can learn things. They can learn languages, new skills. And young adults can learn. But that the adult brain was less capable of learning. Then in the late '90s, it was Dr. Kilgard, in collaboration with his colleagues, that discovered that indeed, the adult brain can change massively if the right conditions are set. His work showed that if specific neuromodulators, meaning acetylcholine, norepinephrine, serotonin, or dopamine, are triggered to be released in the adult brain, you can achieve massive rewiring of brain circuits and learning, even as an adult. This opened up an entire new field within neuroscience, and of course, has profound implications for health and disease. It's also completely changed the way that we think about learning, longevity, and brain health. More recently, Dr. Kilgard's research has focused on vagus nerve stimulation to precisely control the timing of neuromodulator release. As you may know, the vagus nerve connects the body with the brain and the brain with the body, and by stimulating a particular branch of the vagus nerve pathway, his laboratory has shown that people can overcome debilitating conditions such as tinnitus, stroke, and even restore mobility to people who have suffered spinal cord injuries. During today's episode, we discuss the specific actionable strategies that you or anyone can use to rewire your brain at any stage of life. So as you'll soon see, Dr. Kilgard has an exceptionally clear and practical understanding of how to apply what we know about neuroplasticity so that you can learn better and improve your brain health. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero-cost-to-consumer information about science and science-related tools to the general public. In keeping with that theme, today's episode does include sponsors. I have a brief announcement to make about my upcoming book, Protocols: An Operating Manual for the Human Body. I've completed the book now several times, and yet it's not quite ready for release, and I'll tell you why. Some years ago, somebody I highly respect in the research science field that I was working with on a project said to us as a group, "If you have the opportunity to make something better, you do it." Now, I realize that runs counter to what we all so often hear, which is, "Never let perfect get in the way of completed." But I must say, when it comes to providing the public health protocols, I absolutely insist that you have the most up-to-date science and information in the Protocols book. And so that's the reason why I've decided to go through and basically revise each and every chapter, adding some things based on new research and improving the protocols overall. I strongly feel that's my obligation to the data and to all of you. I confess, part of the delay is also because I've decided to do all the illustrations for the book myself. As a consequence, my book is now going to be released in September 2026. If you'd like to pre-order the book, it's available in English and other languages, and yes, it will be available in audio form. If you'd like to pre-order, go to Protocolsbook.com. Thank you for your patience. I'm excited to share the book with you next year. And now for my discussion with Dr. Michael Kilgard.

2. 3:24 – 5:13

   Neuroplasticity

   1. AHAndrew Huberman3:24

      Dr. Michael Kilgard, welcome.

   2. MKDr. Michael Kilgard3:26

      Nice to be here.

   3. AHAndrew Huberman3:28

      You and I both share a fascination with neuroplasticity, the ability for our nervous system to change itself for better or worse. So to start off, let's just talk about plasticity, what it is, how plasticity in childhood differs from plasticity in adulthood. I know how I think about these topics. I'd love to know how you think about neuroplasticity and why you've essentially devoted your professional life to studying it.

   4. MKDr. Michael Kilgard3:52

      Yeah. I mean, I don't love the word. "Plastic" makes it seem like something artificial and, and, uh, uninteresting. But the idea that the brain can change is a new idea. We used to think everything was hardwired and you are the way they are and nothing can change. Uh, now we know that you're making new connections every day, every time you learn something new. And that change in our way of thinking about things has implications up and down the aisle on how we interact and everything we do. The science of it, oh, is so exciting. They, the types of experiments that have been done, the ways that you can literally see these new connections. Our forefathers 100 years ago could only look at dead tissue and imagine all the changes and excitement that was going on, Ramon y Cajal and others. Uh, but now we can, real time, watch these new connections and imagine that there's not hundreds of them, there's not thousands of them, there's not millions of them, there's not billions, but there's trillions of new connections every second of your day are trying to decide, should I strengthen this one? Should I weaken this one? Or should I leave them the same? Uh, and that idea that your brain is as active as you feel is so different than what we were told. We were told, "You've got this brain. It's very dangerous. You should wear a helmet, and you should not mess with it." Uh, and the fact that it's alive and moving, uh, to me, is just much more consistent with my experience with, uh, my own inner life and interact with other people. Uh, so the fact that the science matches the everyday experience, I think is one of the most, um, enlightening parts of

3. 5:13 – 9:37

   Child vs Adult Plasticity, Childhood Development & Learning

   1. MKDr. Michael Kilgard5:13

      those experiments.

   2. AHAndrew Huberman5:14

      So when you think about developmental plasticity, uh, which I sort of been from birth up to about age 25 is what we always hear, "Oh, you know, up until age 25, the brain is ultra-plastic, and then after 25, it's much harder to change, but it can be done." You have kids. When you were raising your kids, given what you know about neuroplasticity, what were some of the thoughts going on in your mind about things that you should do or shouldn't do? I know you're not giving parenting instructions, but I think, uh, there are many parents out there. Uh, all of us were children once or perhaps still are, and are curious, like, how does a neuroscientist who works on neuroplasticity think about learning in general and also just passive exposure to life? Uh, because as a child, every day is new learning.

   3. MKDr. Michael Kilgard6:01

      I mean, they always tell you, "Don't sweat the small stuff," and then you learn every little thing matters, and you start sweating the small stuff.

   4. AHAndrew Huberman6:06

      (laughs)

   5. MKDr. Michael Kilgard6:06

      You start realizing that the kinds of mobile you got matters. That it's, uh, interesting. I, we had a mobile, and the mobile would go around in a circle, and it was just boring. I thought it was uninteresting, and I'd, I'd move it so that it would bump into something and do something a little more interesting from time to time. Uh, my kids spend a lot of time looking out into the natural world, so there were birds flying and coming and going, and not-predictable kinds of patterns. And again, tried to avoid some TV. But the idea that we're kind of in a hurry. You've got to hook up all these neurons that you... You know, being an adult is going to happen fast, and you've got trillions of connections to make. Every experience is contributing to that. So, bedtime stories and songs and walks in the park are all making those changes. Uh, that's surprising. It's surprising that all that stuff matters. Um, but it does. And so from my point of view, um, the fact that the young brain is a sponge and that every little background sound, little clicking sound, road noise, all those things have the potential to impact the way the brain is wired is, is a cautionary tale. It makes you worried about having the wrong sounds in the wrong place. But of course, you don't really know exactly what the best sounds are going to be, the best sights, the best, uh, friendships, and all the rest. Um, so neuroplasticity is, uh, a gift to all of us. Um, and it makes the point that the details matter. But it also makes the point that there's lots of details, lots and lots of experiences. No one, um, formative experience is going to ruin some kid's life, uh, and I think that's a little bit relieving as well.

   6. AHAndrew Huberman7:28

      Yeah. There's plasticity in both directions, I suppose. You can wire things in one direction, and if, uh, if you don't like it or if your parents don't like it, you can wire it back in another direction. Although, as we both know, there's a little bit of an asymmetry to that. It's kind of easier to get negative experiences wired into the brain, and a little bit harder, or a lot harder as th- the case may be, to undo those. So, um, I guess it was the early '90s when we heard a lot about the so-called first six years. There was this emphasis on zero to six years of age, uh, as being so critical, and this had parents who understandably were interested and concerned with their kids having the most, n- you know, knowledge, the most capability in life, the best life. Um, it had parents playing classical music to kids while they were asleep. It had them doing multiple sports. There was this idea that you have six years to, like, cram everything in there. I think we now understand that's not the case, that those first six years are critical, but there's a long window for plasticity. Would you agree?

   7. MKDr. Michael Kilgard8:30

      Absolutely. No, I mean, I think we, we worry about doors slamming shut. Uh, we worry about, uh, every little sight being the thing that's going to define a child for the rest of their lives. And that's just not the case, right? Lots and lots of hours. We always talk about 10,000 hours to be good at anything, and you realize you get a lot of 10,000 hours. I mean, you really do, and not just your language abilities. Each person knows 100,000 words. Imagine. You don't have to sit and teach the kids every little word. They're going to pick them up. They're just in an environment, and 100,000 is a lot of words to imagine knowing their definitions, knowing their meanings, and all the rest. Uh, and the same thing of finger movements. Again, whether they're going to be a violin player or a soccer player, all the dextrous movements that have to go with that. We as coaches and parents try to train that, but really the kid is training themselves. They're figuring out how to do all that by practicing, seeing what works and what doesn't work. We can just set an environment where that's possible and where they can succeed and not quit. Uh, that's really one of the big challenges. Like you said, a kid gets exposed to food, they get sick, and now their brain has figured out that food might be poison. But it might be wrong, and they might end up with a plastic event in their brain that turns off a pathway for a long period of time. And it can really be hard to, to, to undo that kind of

4. 9:37 – 12:41

   Sponsors: Eight Sleep & Wealthfront

   1. MKDr. Michael Kilgard9:37

      work.

   2. AHAndrew Huberman9:38

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5. 12:41 – 21:13

   Kids, Real vs Artificial Experiences & Balance, Video Games, Natural World

   1. AHAndrew Huberman12:41

      description. What are your thoughts about when a kid has a particular love for one activity, p- perhaps to the exclusion of everything else because time is limited? Assuming that activity isn't outwardly destructive, like they're not harming themselves or others, uh, it doesn't involve the use of, you know, chemical substances, that kind of thing. But let's say a kid just loves to read, and w- and unless forced not to, would just use every possible moment to read or play video games or do any number of different things. You know, then the self-directed learning that they're doing, the plasticity, is being fed by these things that I know we're gonna talk a lot about today, neuromodulators, right? We know these as dopamine, uh, norepinephrine, epinephrine, serotonin, acetylcholine. Uh, these things amplify, in many cases, the activity of certain circuits. Like, if one of your kids was doing something at, say, age eight, nine, 10, 12, was doing one thing almost to the exclusion of everything else when they had the opportunity to do something, like free time hits, they're doing that, would that excite or concern you in terms of what you know about plasticity?

   2. MKDr. Michael Kilgard13:50

      Um, my kids know that it would depend upon whether I viewed, in my judgmental nature, the experience as a real experience, an adventure, something that's happening, or an artificial or a fake one. My concerns about video games and other things like that are these could be really detrimental 'cause they don't have the statistics of the natural world. If you're engaged, as my daughter was, with people, and you just want to hear people talk... She was infinitely fascinated by, "What are they talking about? What are they thinking about?" And there was no end to her interest in people. People are interesting. People are complicated. Uh, on the flip side, if you're talking about a video game, I won't name any particular one, um, where it's an artificial currency, where you're, you're sort of constrained to be interested in it, similar to what would happen in Vegas where you'd say, "I'm gonna let you win at first (laughs) so that you can get hooked on it, and then I'm gonna adjust it," well, you're being manipulated actively. Most experiences kids are interested in, they're not being manipulated. It's a game. 50% of the time you win, 50% of the time you lose if you're playing football or soccer. But there are some experiences where someone is actively messing with you, uh, in a way that can be negative, so we would always distinguish between that. Kids would share they had this great experience on a video game or a great video they saw, and I would just point out, "That wasn't an experience you actually had. That was an experience you watched online or something else or that was a video." And we just kept emphasizing that there's something different about real experiences, and for me, that's about the statistics. That's about the pattern in the natural world. You're working the visual system. There's spatial frequencies. There's distributions. There's, uh, peripheral vision. In the auditory system, there's reverberations. There's all these things that you can remove if you want to and simplify the world down, but we evolved in an environment where there were risks. There were opportunities. There were ways for us to explore our smell, our touch, our taste, and they were all integrated together. When they all get separated and the touch doesn't have anything to do with the, um, the sound, and the sound doesn't have anything to do with the sight or the smell, there's a potential for them all to sort of drift off on their own and not be integrated in a way that I think is most helpful. So for me, it was just, is it real? Would my grandparents recognize this as a good way to spend a day? Uh, and if it wasn't, I'd at least take some time to think about whether or not there might be some negative consequences of that artificial environment.

   3. AHAndrew Huberman15:58

      I think it's really interesting that you say certain experiences aren't really experiences because they don't include the full array or as large an array of the, quote-unquote, "statistics of the natural environment." And I think for us as neuroscientists, we're used to using this language, statistics of the natural environment, and you pointed this out, but I just, uh, want to go into this a little bit, uh, more deeply. You know, in a three-dimensional world like the one we're in now, sitting across the table having a conversation, or people listening to this and watching it, or both, there's a lot of information that we're not aware of, the depth information, motion information, lack of motion information, right? If I suddenly start waving my arms around, that's, uh, you know, gonna pop out because nothing else really is moving that much.

   4. MKDr. Michael Kilgard16:40

      Yeah.

   5. AHAndrew Huberman16:40

      I think people, uh, probably need to hear it from you in order to really appreciate how a developing brain is really a template for wiring all that capability in. You know, this time from birth until about 25 is really when all the predictions about the world are being formed, and I think we hear so often about, "Okay, make sure they learn an instrument, play a sport, uh, they're reading, um, maybe learn another language." By the way, (laughs) learn another language. You can learn other languages without an accent up until a particular age, and then it becomes very, very difficult. Uh, I wish I had learned another language. That's why I say that. I- i- you know, the... We hear about all the things that ought to make kids more, quote-unquote, "functional adults" once, once they get to adulthood, but what you're describing is a pretty kind of like low-level but foundational aspect to just building a, a brain that can do a lot of stuff and that wants to forage for interesting real-world experiences as an adult. So, um...When you were raising your kids, did either of them like video games particularly?

   6. MKDr. Michael Kilgard17:40

      Yep.

   7. AHAndrew Huberman17:41

      Yep?

   8. MKDr. Michael Kilgard17:41

      My son liked video games.

   9. AHAndrew Huberman17:42

      Uh-huh.

   10. MKDr. Michael Kilgard17:42

       My daughter did not.

   11. AHAndrew Huberman17:43

       Yeah.

   12. MKDr. Michael Kilgard17:43

       Um, it didn't end up becoming a significant problem, but, but it was certainly, uh, an interesting agility still. You know, I, I grew up playing video games as well with one joystick, one button. Uh, now it's much more complicated and elaborate, and I appreciate the beauty of it. I appreciate the, the finesse, the dexterity, the complexity. I think it's fantastic, all the things they can do to be running through a complex environment, navigating a map, looking at a certain direction, walking out, watching out for low contrast, uh, threats and, and prizes. Uh, so there's a richness to it that just, undeniable. It's really rewarding and satisfying. Um, the question is just how well does that generalize to other skills you might need in your life? How well prepared are you? And are you able to turn that off, uh, at the end of the day and go on to study for your tests, you know, do the dishes, uh, mow the lawn, whatever else needs to be done? Uh, and I think there are certain situations where it's really helpful, and there are certain situations where it's, it's overblown. And the same is true of reading. I mean, I think, uh, my grandfather was a head librarian at Arizona State University, and it seemed like reading, there's no end to reading. Couldn't we just all do more reading? And reading is great, but there's also restrictions of, uh, from reading. Um, um, Ralph Waldo Emerson's one of my heroes, and he says, you know, "Books well-used are among the best of things and poorly used among the worst." And the idea is, if you could be coming up with your own ideas, maybe you shouldn't need to be following someone else's story and their own adventure. Maybe you should go out and do your own a little bit. And the question of proportions is a challenging one. When it's raining and you can't go outside, maybe that's a good time for reading. When it's a nice day outside, you could be going outside, maybe that's a better time to go find friends and, uh, work on dexterity and skills and, and get some sunlight.

   13. AHAndrew Huberman19:14

       Thanks for mentioning sunlight, by the way. That's a big theme on this podcast across episodes. Uh, so are you telling me that Emerson himself, uh, suggested a b- that, um, the technology of books not be overused?

   14. MKDr. Michael Kilgard19:26

       He did. He absolutely did.

   15. AHAndrew Huberman19:27

       Which is a wild-

   16. MKDr. Michael Kilgard19:28

       Yeah.

   17. AHAndrew Huberman19:28

       ... thought in this day and age.

   18. MKDr. Michael Kilgard19:30

       No, it really is, and I love that, that's what I mentioned about sort of our grandfathers, the wisdom that people knew from a long time ago. He had an intuition about how we follow into habits. Um, he would find out that as I walk, I make paths, and the paths you just see, I keep doing the same way. And he would look at that and kind of intuitive that that's a habit that I'm forming that may be helpful, but maybe I should try to take a different way, uh, the next day. Uh, talked about the idea that consistency is overrated. Uh, he had this line, uh, from an American scholar, um, "Consistency is the hobgoblin of little minds," that you feel like whatever I said, I have to keep saying that, keep being right. And the real world will teach you no. If you're wrong, the world will teach you. If you think you're right about something, all your friends will teach you that you're not. If you think this is the best way to kick the ball, you'll find out someone else has a different way of doing it, or play the instrument or whatever it is. So I think that idea that there's some humility about there is no optimal, there's no perfect way, there's always some new way of learning is something that, uh, I appreciated in reading books, and it's awkward that here's someone writing a book telling you not to listen to people in books-

   19. AHAndrew Huberman20:32

       Mm-hmm.

   20. MKDr. Michael Kilgard20:32

       ... and go out and live the real world, and I think a lot of us are coming around to that, that we need to have our own real experiences and that there's value to that, not just reading about someone else's.

   21. AHAndrew Huberman20:41

       I forget where it appeared, but recently there was, uh, some photo or article published where, uh, an artist had taken images, real-world images of humans out in the world, um, and had deleted the phone from the image in any case where there was a phone in the image. And what you basically see is that people are out in the world staring at their palms-

   22. MKDr. Michael Kilgard21:00

       Yeah.

   23. AHAndrew Huberman21:00

       ... all the time.

   24. MKDr. Michael Kilgard21:00

       Yeah.

   25. AHAndrew Huberman21:00

       And these are, you know, images from the, the last six months or so.

   26. MKDr. Michael Kilgard21:03

       Mm-hmm. Mm-hmm.

   27. AHAndrew Huberman21:04

       So these, this isn't, these aren't paintings. They're not drawings. You really get the impression that, like, we, people are removing themselves from their natural environment almost entirely.

6. 21:13 – 33:42

   Social Media & Videos, Kids, Overstimulation & Development

   1. AHAndrew Huberman21:13

      Within the phone, there's something very interesting that I'm curious, uh, what you think of in, for sake of understanding plasticity and what this might be doing to our brains. A picture's worth a thousand words. A video is worth a billion pictures. And I know you're not on social media, um, but if I scroll through an Instagram feed or a Twitter feed, X feed that is, um, I can see 50 videos, 100 videos inside of 10 minutes easily from disparate contexts. It can be sports, dogs, this, that, so

   2. NANarrator21:49

      (laughs)

   3. AHAndrew Huberman21:50

      ... you know, I mean, and the algorithm's obviously deciding what I see. But I don't think there's ever been an instance in human evolution where that was the case. I mean, even with television with 200 channels, you can flip between channels. Okay, I guess you could keep looping, but that doesn't tend to be the case. People eventually would settle on a show or navigate a menu to a show. What do you think this, uh, means in terms of the processing capacity of, of young brains in particular? Like, if your son, I don't know how old he is, but if, but if he, he's still in the developmental window of plasticity or was at one point, if he, or your daughter, if they are seeing 50 videos that are, uh, not really linked to one another in any particular way, that feels like a university experiment where they came into my lab or your lab and we're measuring brain activity and we're trying to see what random videos presented rapidly does to the brain or something. It doesn't seem like a healthy thing, and I'm not trying to pass judgment without even understanding what it does, but this, I can't feel that that would be a good thing for the brain. The brain's never experienced that before.

   4. MKDr. Michael Kilgard22:53

      Well, let's talk about what the brain does. So we know these different areas which you've talked about, locus coeruleus releasing norepinephrine in the brain. Um, when something new and exciting happens, someone claps their hands or pokes your ear, you know, a bug flies in your face, uh, the neurons fire. They're, they're surprised that that happened. If it keeps happening, then the neurons stop firing. So one of the things that's most surprising to me and interesting to me is there are experiments by Richardson DeLong and others, um, recording from these areas, nucleus basalis releasing acetylcholine, locus coeruleus, even, uh, dorsolateral releasing, um, serotonin, is that they're excited the first time, and then they quickly get used to it. And so they're always waiting for what the new thing is. What's the thing that's going to be informative? What's the thing that's going to have, uh, the most rewards? What's the thing that's going to have the most risk? Um, and the problem is we don't know.... what the long-term consequences are of having over and over and over activation of that pathway. Um, we know that if you take a child and just sit them in orphanages for years upon years, they don't come out well. That's pretty clear with animals or humans, that deprivation is not good. But what happens on the flip side when you stimulate and then you over-stimulate? We don't really know. At least I don't know of any clear-cut, well-designed experiments. The suggestion, as you know, is maybe it increases depression and anxiety among adolescents. That, that appears to be what's happening, but there's no causal link because everyone is doing this experiment together. My children watched lots of videos, uh, exposed to lots of things. Uh, it's very difficult to get rid of it. It's sort of in the water, it's in the culture, having a phone and having that restricted view. On the flip side, this generation is great. They got a million things they know about because they were able to time travel and look at things in the distant past, th- look at things in the future, look at things in other countries. Their awareness of people who are different from them is so exciting. So it's hard to balance those two. But in general, the concern for me would be if you max out that neuromodulator release, if you do things all the time, including illicit drugs that push that up, it's intuitive to me that that would then push down all your other experiences.

   5. AHAndrew Huberman24:51

      Mm-hmm.

   6. MKDr. Michael Kilgard24:51

      So I've had the great pleasure of taking my face from the desert world of the, um, Sinai Peninsula and putting it down into the water of the Red Sea. It's miraculous. I mean, the level of colors and movement and textures, and you pull your head back up and you're recalibrated, like this is the moon. There's all this rock. Put your face back down. That contrast to me is real and very exciting. Others have told me that they have taken illicit drugs and had very similar experiences. And I'm not going to say that my experience of real colors and real life forms, uh, and real waves and patterns is superior, it's just my preference. And I think we know people for thousands of years have had these kinds of experiences, looking at mountains and streams and, uh, groups of people. What we don't know is what happens when you take a lot of fentanyl, a lot of methamphetamine, a lot of, uh, cocaine, or, or even nicotine at high levels. We don't know. Um, but the worry is Ben Franklin's "all things in moderation." Probably better to take it slow and make sure you didn't overdo this one. Uh, but I don't know what the negative consequences are going to be other than the potential increase in depression and anxiety.

   7. AHAndrew Huberman25:54

      You were snorkeling on a coral reef in the Dead Sea. Is that-

   8. MKDr. Michael Kilgard25:56

      That's right.

   9. AHAndrew Huberman25:56

      ... the experience you were describing?

   10. MKDr. Michael Kilgard25:58

       Yeah.

   11. AHAndrew Huberman25:58

       Yeah. I love aquaria. I have some at home, and I love snorkeling and, um, s- done some scuba diving. And I agree, when you see the richness of a coral reef and then you pop up, it's like, um, the contrast is a big part of that experience.

   12. MKDr. Michael Kilgard26:11

       Yeah.

   13. AHAndrew Huberman26:11

       But it stays with you, right? It's, uh, I mean, you're out of your element down there. You know, if you're doing scuba, you're more or less like a fish. If you're snorkeling, you're a pseudo fish. (laughs) You know, you're... But when you come back, those experiences stay with you as an enriching experience. Watching a video of a f- of a coral reef, well, that can be relaxing. It, it's a completely different experience, uh, as, as you pointed out. I have to be careful because I want... I'm almost 50 and I want to believe that real-world experiences are better than virtual ones. And now with the, you know, the, you know, huge arrival of AI, which is only going to expand, um, everyone's asking the same sorts of questions. You know, at what point is it true sensory deprivation? I mean, on the one end of the continuum, as you pointed out, uh, sensory deprivation is bad, especially for a developing brain. The other end of the continuum, sensory gluttony is also bad. And we could be talking about food here, right? Starvation is bad and gluttony is bad. Both make you sick.

   14. MKDr. Michael Kilgard27:07

       Yeah.

   15. AHAndrew Huberman27:07

       One kills you faster. Starvation kills you faster. (laughs) Um, but as we've now seen with the rates of obesity in this country, you know, gluttony is, I'm not calling people gluttons to be disparaging of them, but let's face it, people are consuming more calories than they burn for whatever reason. So I think when it comes to sensory input, I have a feeling we're going to arrive at a similar place in a few years where we are going to realize that, uh, we need to set upper limits on h- on how much sensory input and set quality standards for sensory input. Right now, we're just kind of drinking from the fire hose.

   16. MKDr. Michael Kilgard27:41

       Well, and, and how you interact with it and what the ways you interact with are, if the only way to interact with it is flipping the screen, that's pretty limited. And what, the human body does a lot of amazing things. We, the way we can navigate, whether it's skateboards or paragliding or whatever, people can do, uh, fantastic things with their bodies. But if you're not required to do it, we know this principle of use it or lose it. If you don't have that exposure to the sounds of Swedish vowels... When we were born, we could hear all the Swedish vowels, and then we weren't raised in a culture that used them, and they just disappeared. And the worry is that that ability, the natural predisposition of our brains to handle those kinds of inputs, that over time when we don't use it, we'll say, "I guess you don't need this. I guess swimming is not something that you're gonna need to do. I guess..." And a lot of people don't swim, which is fine. But how many of those experiences get turned off, especially at a young age where they're easier to pick up? That's one of the big questions. I don't know. But it makes sense that the kinds of training, the inputs in, you know, junk in, junk out. We used to think... Again, the bodies just grew. Brains, babies just got bigger. That's all that happened. And then we started realizing the things that they saw mattered. At first, we thought, "Well, let's find what they like. What do they like the most?" You may remember these old experiments where they, they found that if you give a baby a face and then you give it an, a cartoon face, it'll look more strongly at the cartoon face, the exaggerated black and white face.

   17. AHAndrew Huberman28:56

       Mm-hmm.

   18. MKDr. Michael Kilgard28:56

       And some babies had trouble disengaging from it. The attention mechanisms were so cued to two black circles and a mouth, and people sold baby mobiles that were these very engaging things that the babies couldn't get their eyes off of. Now, when you go to Babies "R" Us or whatever store, you don't see those anymore.

   19. AHAndrew Huberman29:11

       Yeah.

   20. MKDr. Michael Kilgard29:11

       You see much more naturalistic kinds of things. But there was a moment when we thought, "Well, if the babies like it, give it to them." And then we sort of thought, "Maybe just 'cause they like it is not sufficient. Maybe we should try to do a longer term re- Not that short-term immediate gratification, but the longer term, what does it do that the face I've seen is an extreme f- face, an exaggerated face?" And again, we think back to individual neurons, whether retinal ganglion cells or, you know, uh, cells in fusiform face area, these are parts of the brain that are involved in visual processing. If those areas are wired...... normally, appropriately, then we pay attention to the right cues. Um, it's typical when I'm looking at you when you're talking to look at your eyes, not look at your mouth. But there are a number of people who will be more interested in the movement of the mouth because it's larger than the eye movements, and that's a less effective way to look is to look at the mouth instead of looking at the eyes. These are very subtle things, but some of the microaggressions, microgestures that are critical, not just in our culture but in monkeys, where gritting your teeth might mean one thing and winking or looking away might mean another thing. We want our children to pick those things up and know about how to interact with humans. On the flip side, social media and online culture is part of our culture now too, and so depriving them of that and having them be, um, blocked, deprived of what their culture now is, is also seemed harmful. So for me and my wife, thinking about it, I don't want them to know nothing about the internet, but I don't want them to jump in with both feet and have all of their experiences. So what proportion is that? You know, 20% of your day on the internet? That seems reasonable, maybe. Many people are at 80, 90% sometimes. Uh, I think it might be better to be at 5%, only when you're needing it to reach out or do things. But I don't know the answer to that. We're doing this big experiment, but we've done these experiments before. We did this experiment, like you said, with television, 200 channels. We did this experiment with the radio. We did this experiment with the printing press when suddenly you could go into a library and just, there were books everywhere. What would that do to people? And I'm generally an optimist, you can probably already tell. Uh, humanity's done pretty good so far. The last 100 technologies didn't end things, whether it was machine guns or nuclear war or weapons. So I'm cautiously optimistic, but I think we will rebalance and it won't necessarily be someone telling us. It'll be people figuring out, "I don't feel good when I use this." So both my son and daughter routinely mention to me when they turn off apps, remove, pick your social media. They just need a break. And I think that's, again, a sign that people individually have enough autonomy to figure out for themselves what's working and what's not. But it would be good to have a body of knowledge to reinforce that and make it feel okay. You're not missing out. You're not punished because you turned this off for a few days or weeks.

   21. AHAndrew Huberman31:49

       Yeah, the algorithms punish you for turning it off for, uh, a while. They, it, it favors a pretty consistent cadence of posting and interaction. I'm very surprised that somebody had the good sense to steer parents away from buying mobile, mobiles. We should probably explain. These are like things that you hang above the baby's crib, of course, and they, uh, they spin around. They have kind of like branches on a tree. Uh, uh, they're colorful, they have motion, babies can interact with them safely, this kind of thing. I'm quite surprised, pleased but surprised, to hear that, uh, when the ideal mobile for getting babies to attend, uh, with just the simple faces, uh, was discovered (laughs) that somebody intervened and said, "Hey, just because they like it doesn't mean it's good for them." I mean, everything else in sort of a commercial industry runs exactly the opposite way until we discover it's actually harming us. Um, so I'm positively surprised. Um, I don't know who made that decision, but I'm relieved to hear that if you go buy a mobi- mobile now, it's not the one that would maximally cause the b- the baby to attend. It's the one that's best for their development of the visual system. And I immediately think of iPads.

   22. MKDr. Michael Kilgard33:04

       Mm-hmm.

   23. AHAndrew Huberman33:04

       I mean, you give a baby an iPad, they will, they'll just-

   24. MKDr. Michael Kilgard33:07

       Yeah.

   25. AHAndrew Huberman33:08

       ... be there all day and we think, "Oh, they like it." We sort of know it's not good for them, and yet it's become the digital babysitter that the television used to be. Now, I'm not anti-technology. I mean, I grew up in Silicon Valley after all, and I use technology, including social media. But I guess I'm concerned and struck by, you know, this question of where to draw the line. Um, so in this instance, somebody had the good sense, but this is the, the different... I mean, the, the food equivalent would be sure, I'm sure kids would prefer ice cream.

   26. MKDr. Michael Kilgard33:37

       Right.

   27. AHAndrew Huberman33:37

       They'd eat it all day long.

   28. MKDr. Michael Kilgard33:38

       Right, that's right.

   29. AHAndrew Huberman33:38

       As opposed to things that are more nutritious for them.

   30. MKDr. Michael Kilgard33:40

       But there are consequences.
7. 33:42 – 39:23

   Early Language Development, Passive vs Real Experiences, Kids & Adults

   1. MKDr. Michael Kilgard33:42

      yeah. I mean, there's a, a bunch of things that brings to mind. Um, one is how studying the brain informs how we should use our brains. One idea, as you mentioned, was, uh, language, early language development. Alison Gopnik and other people have looked into, there's contrasts in sounds that we can't hear and so my kids were young, we said, "Oh, we should expose them to all those sounds." And so there's a company called Baby Einstein and they play, you know, Spanish or French or... But we don't really know how much of these languages, um, should they be exposed to. What is the right mix to make them better world citizens, better learners, smarter, uh, more resistant to nerve disorders or whatever. We don't know the answer to that, so we're just running the natural experiment. I tell everybody that being a neuroscientist is way easier than being a parent. There's just too many choices and there's no control group. There's no way to run it again until you find out the actual answer. What's interesting was that it turns out exposing people passively, babies passively, to the sounds from other languages really doesn't change very much at all because there's no interaction. So the Chinese tones or the Swedish vowels, these different sounds, um, when they're not really interacting with you and they're just on the screen, you don't pick them up, which is really fascinating that your brain already knows that's a TV. And how does it know that? It knows it because your interactions with it are so limited. I took Spanish as a kid and they said, "You should watch telenovelas and learn Spanish and, y- you'll learn the culture and you'll pick it all up. You'll get the humor and the jokes." I didn't learn that much from it because no one was talking to me. I was watching passively. And so we now know that when you're actively engaged, you're going to have better neuroplasticity, better generalization, you're going to better connect it than when you just sit back and watch. Here, swiping is not exactly no interaction. You have some, but it's pretty impoverished, pretty limited. So I suspect a lot of it isn't that bad, just kind of comes in one ear, goes out the other. But that also means those hours aren't spent doing something else, playing in the mud, getting your immune system developed, interacting with children, hitting things with a ball. You may aren't taking as many risks. Maybe that's a good thing. Maybe you're not getting as many head injuries as we used to get. Maybe that's a good thing. So I think we got to take the good with the bad, but in general the idea that neuroscience is accessible and that we learn that our experiences really matter, I think that's the exciting part. Why is ChatGPT so smart?We trained it on every word we ever wrote, the whole species. And then that went into these billions of connections, and those billions of connections produced something that's relatively sophisticated. The same thing for a child. Here's a child, the experiences they have matter. All the kids are gonna learn to walk, or almost all of them, by a year, but a lot of things happen during that year. A lot of falls, a lot of tumbles, a lot of uts, a lot of stairs. Um, and so I think for me, having those, a large fraction of experiences be what I call real, having statistics of the natural world, things that our grandparents would've recognized and been familiar, that's likely to be something that's good for your brain both as a youth as well as, as a full-grown adult. Then you ask the question, how about at the end of life? At the end of life, is it now okay? My brain's already done. Can I swipe to my heart's consent? Can I watch Wheel of Fortune or whatever I want all day long? The evidence suggests it also causes depression and anxiety. If your day doesn't involve other people communicating, if there aren't surprises, someone knocks on the door... When I was a kid people knocked on the door a lot. It was a big surprise. That's not a surprise children have that much anymore, someone just randomly knocking, 'cause they would've texted. And so the surprises are now coming from da-donk, I got a text. Oh, Bill wants to come over. As the pa- population ages, many people are likely to find out that having too many experiences that are disconnected from reality, that are just a show that's made to be engaging and interesting, isn't as good as getting on a boat and driving someplace, visiting some location, getting on a bus, um, driving, flying, wherever it is. So travel gives you different experiences. You smell different smells, you hear different things, and those engage, again, those neuromodulators. Those neuromodulators then help make changes, because the vast majority of inputs we take in, we just throw away. We're not memorizing every place I ever was, every place I ever set my keys, every word everyone ever said. I mean, none of us are tape recorders. We're picking which moments are the moments that are useful, and that's hard to know because we don't know what the future looks like, but we're making guesses based on what the past looks like. And so when the past is abnormal, robotic, uh, exaggerated in its novelty, um, we make changes assuming the future's gonna look like that, and the future may not be. The future may be a job, and it may not be this exciting, and it may be hard to stay focused for eight hours a day if you're used to something exciting happening every two and a half seconds and I now have to do a job. For, for me it's writing where I have to sit and stay focused for hours at a time trying to put a handful of ideas together in a way that other people understand, or try to develop a new treatment for someone who's suffering from a serious neurological psychiatric disorder. It just takes hours and hours of focus. And for me, fishing was helpful for that. Sit there with your dad and just fish for hours (laughs) and you go, "What are you doing?" "We're not catching. We're fishing. It just means we have a line in the water and there might be a fish, there might not be." And it may only be 1% of the time you're catching a fish. It might be 1/10 of a percent of the ti- of your- time you're catching a fish, but that's enough because the time spent in anticipation and waiting and preparation, those were meaningful times as well. So I think there's a little bit of a shift toward what are the key parts? Is it the dopamine hit, the exciting, the novelty part, or is it all that other stuff? And we're now learning from the training of these networks all of it matters. All of those inputs, all of those syllables, all the junk words matter, um, and so I think that shift toward thinking we know what's important, the stuff we think of as important, that may not be all of it. All the rest probably plays an important role too.

8. 39:23 – 42:44

   Sponsors: AG1 & Carbon

   1. AHAndrew Huberman39:24

      I'd like to take a quick break and acknowledge our sponsor, AG1. AG1 is a vitamin mineral probiotic drink that also includes prebiotics and adaptogens. As somebody who's been involved in research science for almost three decades and in health and fitness for equally as long, I'm constantly looking for the best tools to improve my mental health, physical health, and performance. I discovered AG1 back in 2012, long before I ever had a podcast, and I've been taking it every day since. I find it improves all aspects of my health, my energy, my focus, and I simply feel much better when I take it. AG1 uses the highest quality ingredients in the right combinations, and they're constantly improving their formulas without increasing the cost. In fact, AG1 just launched their latest formula upgrade. This next gen formula is based on exciting new research on the effects of probiotics on the gut microbiome, and it now includes several clinically studied probiotic strains shown to support both digestive health and immune system health, as well as to improve bowel regularity and to reduce bloating. Whenever I'm asked if I could take just one supplement, what that supplement would be, I always say, "AG1." If you'd like to try AG1 you can go to drinkag1.com/huberman. For a limited time, AG1 is giving away a free one month supply of omega-3 fish oil along with a bottle of vitamin D3 plus K2. As I've highlighted before on this podcast, omega-3 fish oil and vitamin D3 K2 have been shown to help with everything from mood and brain health to heart health to healthy hormone status and much more. Again, that's drinkag1.com/huberman to get a free one month supply of omega-3 fish oil plus a bottle of vitamin D3 plus K2 with your subscription. Today's episode is also brought to us by Carbon. Carbon is a diet coaching app built by nutrition expert Dr. Layne Norton. Now, I've used Carbon for more than three years now, and I have to say, it's among the most powerful tools for nutrition coaching and effective weight management that I've ever encountered, especially if your goal is like mine, which is to maintain or build muscle while also losing fat. Now, I'm turning 50 years old this September, and even though I consider myself in pretty good shape and I've been training for a long time and trying to eat right, one of my goals is to hit 50 in the absolute best shape of my life. To do that, I'm dialing in my nutrition using Carbon, with the goals of increasing my muscle mass, increasing my strength while also decreasing my body fat.I've been raving about the Carbon app to friends and to family and to members of my Huberman Lab team over the last few years, and everyone who's joined me in using it has found it to be tremendously useful. In fact, some of those people are going to join me in my approaching 50 fitness goals and body composition goals. My birthday is September 26th, and so I'd like to invite you to join, if you would like to improve your body composition and fitness, to also use the Carbon app. Now, there are a lot of apps out there that are focused on fitness and nutrition, but what makes Carbon different is that it doesn't just hand you a one-size-fits-all plan. It actually learns your metabolism over time and it adapts your program based on your results. It also allows you total flexibility in how you eat. So if you're looking to take a smarter, more personalized approach to your nutrition, I can't recommend the Carbon app enough. To try Carbon, you can go to joincarbon.com/huberman. While Carbon does not typically offer trials or promotions, they've agreed to give a free seven-day trial to all Huberman Podcast listeners. Again, that's joincarbon.com/huberman to get a seven-day

9. 42:44 – 52:24

   Learning & Plasticity Requirements; Focus, Friction, Rest & Reflection

   1. AHAndrew Huberman42:44

      free trial. You and I both c- come from lineages of neuroscientists that focus on neuroplasticity. My lineage, through Hugh Boone Wiesel, uh, were really about the developmental plasticity piece. Your lineage, through Mike Merzenich and others, it's really about the adult plasticity piece. So I'm hoping that as we move forward, you'll be willing to, um, do a little bit of an experiment with me. Uh, as you were talking just now, uh, what I realized is my- my real wish, not just for this conversation, but in life, is to come up with some real understanding of what the requirements for plasticity are in a way that regardless of how the world changes, AI, social media, love scuba diving, snorkeling, et cetera, regardless of the inputs, that we can make the best informed choices. Understanding, of course, that not all of life is about rewiring ourselves. Some of life is about enjoying ourselves. So, i- if I may, I'm gonna just put up a couple of things on the- the, um, non-existent, um, whiteboard here, uh, to frame in people's minds. I think we understand, just by observation for thousands of years, but also now from science, that from the time we're born till about 25, there's a lot of passive, uh, experience that helps reorganize the brain. Negative experiences get kinda stamped down. They can be undone through s- through work like talk therapy and maybe some neural augmentation that we'll talk about later for PTSD. This is also true in adulthood. But that it's clear that there are at least two things that are required for plasticity at all stages of life. One is some degree of focus, right? You just can't be stuff in the room. Can't be classical music playing in the room. You're not gonna build a Mozart or even somebody that can play even a fraction of an instrument. Uh, but if a kid learns an instrument-

   2. MKDr. Michael Kilgard44:31

      Yeah.

   3. AHAndrew Huberman44:31

      ... they can do it. If an adult really focuses and tries to learn an instrument, they can do it. It's just slower in adulthood, in most cases. The other piece that I'm aware of, and tell me if I'm off here, um, is sleep is required. A lot of the rewiring of neural connections actually occurs during rapid eye movement sleep and deep sleep. Y- you can't just focus and just work infinitum. You need sleep. You need rest for the rewiring to occur. But as you're telling me about these experiments, and by the way, I d- I was not aware of this experiment that kids will attend more to a, uh, kind of a cartoon face than to a- a real face, I was not aware of that. Um, as you're telling me about that or fishing or we're talking about music learning or language learning, uh, I believe the best way to learn a language is to place yourself into an environment where it's critical that you learn it, like go to a foreign country, and if you need to learn how to navigate by virtue of understanding and speaking some remnants of that language, you're gonna use- learn it much more quickly than sitting in Spanish class back in the United States. Uh, so I'm wondering if, in my mental model of how to change one's brain, that in addition to focus, which requires alertness, right? In addition to focus and periods of sleep for the rewiring to occur, maybe I can, if you have a better word let me know, but I want to introduce this, an, uh, an element of friction. That there needs to be focus and friction, right? Because with the kid looking at the face, the- the cartoon face, there's focus but there's no friction to get there. With friction, like, there's some element of- of self-generated work. Like with the snorkeling, you have to get wet.

   4. MKDr. Michael Kilgard46:03

      Yeah.

   5. AHAndrew Huberman46:03

      You have to go under the water. You have to put the mask on. It's kinda weird to breathe through a snorkel the first time you do it. It's kind of uncomfortable. Um, there's- there are a bunch of things that go with it that make that experience so much more enriching in terms of how it rewires the brain. And traumatic events, unfortunately, engage focus and friction.

   6. MKDr. Michael Kilgard46:21

      Yeah.

   7. AHAndrew Huberman46:21

      So it meets this requirement. So I'm trying to come up with a table here, and as scientists, we should try and disprove what we're putting up, right? Um, but I feel like what one wants is just enough friction, a lot of focus, and then a period of rest in order for plasticity to occur. And maybe in a video game, there- there isn't enough friction. Um, your daughter, being i- involved in, uh, very interested, rather, in real world human experiences, it's- it's a pseudo-random walk. I mean, there's some regularities about how humans interact, but it's kind of a near infinite space. And it certainly is valuable to have so- social-emotional, uh, intelligence (laughs) -

   8. MKDr. Michael Kilgard46:59

      Yeah.

   9. AHAndrew Huberman46:59

      ... we know this. So what are your thoughts about, uh, about needing to work in addition to focus in order to get meaningful, and when I say meaningful, I mean really adaptive plasticity, stuff that makes us smarter, makes us better people, makes us feel more fulfilled? I mean, it's not all about, uh, you know, test scores. Um, but a really good life is one in which, you know, you feel like the things you're doing have meaning.

   10. MKDr. Michael Kilgard47:22

       Mm-hmm.

   11. AHAndrew Huberman47:22

       You don't look back on the past year and go, "Yeah, that was just a bunch of shmooey experiences."

   12. MKDr. Michael Kilgard47:27

       Yeah, I mean, to- to start on the part you ended on, I mean, I- I really think reflection on these topics, this is another one that was a big surprise, is that thinking about it later also rewires your brain, not just the sleeping part when you're clearly thinking about it and turning it over in your mind-

   13. AHAndrew Huberman47:39

       That's a very good point.

   14. MKDr. Michael Kilgard47:39

       ... but as you're on the way home from the game...

   15. AHAndrew Huberman47:42

       Hmm.

   16. MKDr. Michael Kilgard47:42

       ... as you're planning to drive to the game, uh, or the date, or the, you know, business appointment, or, or, or whatever it might be. Um, that idea that it's not this all the learning doesn't happen at this one moment, but there was some preparation that went into it. There was the actual event, which often has the friction you're describing where there's some engagement and, and decisions are being made, um, where there's, uh, information being transmitted and information being gained. Uh, and then this period of reflection where you're wondering about it, you're thinking about it. For me, often, looking back over my pictures, uh, either of having a child or, or going on vacation is helpful in reorganizing it and reframing it. And for me, those are helpful things to do. But the idea that this is all happening at one snapshot, that's how we used to think of it. We used to think of it as light bulbs went off, you memorize the picture, and you're done. But that's not how any of the ideas, it's not how math is viewed, it's not how language is organized in our brain as a, a series of these memorization events. We're trying to make use of it, and what's gonna be useful is hard to anticipate, hard to predict. So I like to think of it sort of from an information point of view. How many bits of information? So a bit of information is just a yes or a no, and we now live in a world where a floppy drive doesn't have a kilobit. You know, you're not a mega-

   17. AHAndrew Huberman48:51

       Some people won't even know what a floppy drive is, but I'm, I'm, we're, we're dating ourselves, so that's-

   18. MKDr. Michael Kilgard48:55

       Yeah. Y- you could get gigabits. You can get terabits. So we're talking about billions, trillions of bits, and you wonder how much did you learn when you were going up to the plate and you were gonna hit the ball? Well, there's this pitcher makes a particular look when he's gonna give a slider. This person gives a particular, uh, glint in their eye when they're about to say something mean. Um, each way you watch that person is giving information about what's happening in the future, but you have to be there and you have to see that person having that experience. Now, as the ball is traveling down to you or as the person is about to, you know, uh, pull the ball away from you in the Charlie Brown analogy or whatever the experience is, having that sequence of events, you have a prediction. It's pretty low reliability that this is gonna be a slider. Then I start to see, hey, it looks like a slider. Then I swing at it and I miss, and I say, "That was a slider. I missed that one." Uh, then I think about it at the end of the day, and I go back, and for many of us, you dream about it. What is all that about? My original interest in neuroplasticity actually came 'cause something happened to me, not something I chose to happen. I worked in a lab, um, uh, in college squeezing, um, the, um, salivary glands of Drosophila, so the little maggots and the fruit flies. Um, if you squeeze them, they have these banded patterns, which is where all their DNA and their chromatin and their organization of the DNA is organized, and my job was to look and find what looked like barcodes. So, it would be a thick line, thick line, thin line, thin line, thick line, thick line, thin line.

   19. AHAndrew Huberman50:29

       Wait. In the saliva?

   20. MKDr. Michael Kilgard50:30

       It's actually in the cells. They're, they're, um, it's this incision, so about 900 cells all fused together to make one cell. All the DNA then aligns when you stain it. Um, this is in Ron Davis's lab at Baylor College of Medicine. But when I would close my eyes, I didn't see what I normally saw. What I saw were these bands because I'd been staring every day at these patterns, and that happened to me several more times. When I g- spent a lot of time with that focus and that friction you're talking about, suddenly you start thinking about it differently. I had a conversation with a young man a few days ago. Uh, his native language is Spanish, but he told me, "I think my native language is English because I only think in English. And when I talk to my mom, I have to translate. Uh, and they told me when I took Spanish, you'd eventually dream in Spanish, and I did a few times, but I never quite got good enough." So that idea that when you have a really significant experience, you can close your eyes and see it. I believe that baseball pitchers are seeing the balls being thrown, the signs being given. I believe that someone who's playing violin really well or a neuroscientist who's doing surgery, they see those things, and that's a repetition. We now know from Olympic skiers that if you do all your time skiing, you're gonna wreck your knees. So they spend a lot of time in visualization. They spend a lot of time imagining what's going on, stepping through the motions because it's too dangerous to go down the hill at that speed too many times. You'll eventually wreck your knees or break your back. But practicing it can be done offline, and that practicing, the neurons don't know. So long as you're engaged, so long as you're modified by it, that's sufficient. The problem is you're not learning anything new if you're just visualizing it. Where's the new effe- where's the feedback from the world? There's not, but you get the repetitions. And so that idea that we can combine, and again, many, many traditions for thousands of years have had these kinds of notions, you should go back and repeat these aspects to us. We need that extra benefit, certainly that we should sleep. There are no cultures that say don't sleep. (laughs) Um, these are

10. 52:24 – 1:02:51

    Brain Connections, Complexity, Life Experiences & Plasticity

    1. MKDr. Michael Kilgard52:24

       well-received, good ideas. We're now learning, how does that work? And I'm personally excited about the idea that it's about the connections. We had this idea from thousands of years ago. There are four or five things that could be in balance or out of balance. They were famously blood, phlegm, black bile, and yellow bile, and they could be in different levels, and the levels were all that were needed. And that made a lot of categories because with four things at several different levels, you can make lots of categories. Uh, the Myers-Brigg Personality Test, you take a few dimensions and you can kind of explain anything. But whether that's really how we work, where we really are too much blood, too much bile, too much phlegm, or even too much serotonin, too much norepinephrine, too much dopamine, maybe there's more to us. Well, what could it be besides that? And the answer is, I think, the experiments from our forefathers, Ramon y Cajal, uh, Emelo- uh, Emilio Golgi, said it's the connections. And we went, "What do you mean connections? What, what would the connections do?" And now we know from some beautiful studies coming out recently, it's 150 trillion of these things, inside my brain, inside your brain, inside each of our listeners' brains. Uh, and how did they get to be the way they are? Did the genes make them? The genes? There's only three billion base pairs in the genes, not nearly enough.... we only have 20,000 proteins. How could 20,000 make 150 trillion? They couldn't. Genes are critical, they set us up to learn, but they're not enough to tell us how we work. And I think that's true. But the genes are interacting with our experiences. As we listen, as we hear, our brain is being rewired. Whether it's for Japanese, or English, or Swedish, whatever it might be, our brains can learn anything. We can fly the space shuttle. You and I can fly the space shuttle. We can do brain surgery. All of us can, just takes practice. That's the miraculous nature of the way our neurons work. And what's surprising to me is I think we're close to figuring it out, how do the neurons work. 1949, this guy Donald Hebb said, "Fire together, wire together." That's it. A lot of us went, "Does that make any sense? If all of the neurons who fired all wired together, wouldn't everything just fire together and everything just wire together and you'd have a seizure?" And the answer is that's exactly what happens. So his intuition, though partly right, that the covariance, the co-occurring of these events, is an important aspect of learning. It's not so simple. We found out that the neuron that fires a little late, they both fire together, but the neuron that fires a little bit late, instead of long-term potentiation, strengthening the connection, we get long-term depression, weakening. We've been working on the brain a hundred years, but we really only figured this out about 25 years ago. And then the fact that none of that happens, no firing together, wiring together, no out of sync, fail to link, none of that happens if the neuromodulators don't arrive. And the neuromodulators arrive a couple seconds later. So the timing, whether to strengthen or weaken, is a millisecond, a thousandth of a second. Says strong or weak? Which way should I go with it? And then I've got this two-second window that says sometime within a couple seconds, did it work? Was that a win or a loss? And if nothing happens, if it just wasn't important at all, then it all just gets flushed. In one ear, out the other. You just forget it. But when something exciting happens, you get release of acetylcholine, norepinephrine. These things go into the brain, they bind to receptors, they change what's happening inside the cell. And that computation is really sophisticated, and we don't have 100 billion things making that computation. We have 1000 trillion running that computation, and that computation is much more sophisticated than the computation that's happening when you train a large language network. Most of your listeners will have heard of artificial intelligence, machine learning, have some basic idea, but th- we know how that works, 'cause we built it. And it doesn't work how you and I work. There's a big, giant global learning signal, and we just keep running around feeding it back in, and everybody learns this is the right answer, and it threads through the entire network. Right and wrong is told to every single network, neuron in the network. It's something called gradient descent. And that process of improving the network, making it better and better and better at predicting has led to the revolution we've seen in artificial intelligence. What's cool is that our network is cooler. It's way bigger. ChatGPT has 540 billion weights. We're 150 trillion. So that makes us 500 times, each of us, 500 times bigger in scale. And instead of requiring huge amounts of energy, a light bulb is all it takes. Eat a hamburger a day, eat plenty of food, you can learn all day long with that amount of energy. There's not that much energy in a hamburger. Um, and that's miraculous. And so I think there's a lot of worry that when we learn about the brain, it will devalue humanity. We'll be less impressive. We'll be less exciting. I've just seen the opposite my whole career. If we were just genes, then you'd have eugenics, you'd have all these problems. You'd have people who are valued based on whether their genes are right or wrong. Turns out the 20,000 genes doesn't explain us. The hundreds of cell types don't explain us. It's the synapses. I think for a long time we were hoping there'd be an easy fix. If someone had a problem, it'd be nice if they just had too much blood. We can give them some leeches, drain the blood out, they'd be back to good. Right? That's how George Washington died. But now we're learning most people don't have four or five things that are right or wrong. They've got billions. But they're all changeable at any stage in life. They get really hard. Don't disagree to lose an accent, for example, or to get over a traumatic event. It could be really difficult. But the fact is, the brain is plastic till the very day you die. And that ability now to get our head around what do billions of connections mean, what is all this information for? It's informing me. Not just to make us better to be, better to beat someone else on a test or anything else like that, but it's just part of who I am. When I look at a cloud, I've never seen that cloud before. When I hear a baby coo or I pet a cat, all those experiences are really information-rich. Right? Different cats feel different. Different clouds look different. Different babies make different sounds. And the fact that I get my unique experience, you get your unique experience is what our great-great-great-great-grandfathers told us, that we were unique and special. And then a lot of people looked at the clockwork universe and said, "No, no, no, it's all very deterministic, it's all very fixed, it's all very rigid. You're just a machine that does what it's told." Doesn't really seem right. The math guys now tell us as soon as you put three things together in a non-linear way, it's hard to predict what it's going to do. And the computer scientists in the world, my brother's one of them, uh, have finally admitted, we don't fully understand what it's doing. We don't even know how you could understand it. It's so rich and complicated, and we're now okay with that. That kind of, uh, humility about what computers are doing and how they're working can reflect back on our own, um, bodies where I don't know exactly why I make every decision. I say lots of things I regret and go, "Ooh, I shouldn't have said that." All of us do. Um, but the idea that I can change it and I can make amends for that, I can say, "That wasn't what I meant to say. I apologize for that." That's really exciting that there's a biological basis for it, and it's this four-factor learning rule where there's some proteins, um, receptors that are having binding of glutamate, serotonin, norepinephrine, all these words you've talked about before, but they add up to something. They don't eliminate me. They add up to me. Uh, I think that's something we can really be proud of, and I think you're getting this information out to audiences is really exciting, because people have the right to know this. Your taxpayer money has paid for all this knowledge. We've learned all this stuff, and it has real implications, whether it's for how we treat people with disability, how we treat our elders, how we treat people who've committed crimes. All these things...... have implications. And I'm not saying everyone needs to become a neuroscientist by any means, but it's not just a curiosity. It's not just a laboratory trick we wanted to, uh, work out. This understanding has implications, and we've been building as our forefathers did in other fields, physics and all the rest. They've built all the way where their model of physics is pretty good. Our model of the brain is not there yet. We're not at that level of understanding everything, but moving in that direction toward eventually being able to find some child or some older person who's got a real problem, they just can't do it. We can switch from a mode of just labeling them, diagnose and adios, to a new mode of, "How can we assist you?" And it might be changing lifestyles, changing diet, changing, uh, experiences, uh, changing rhythms, changing friendships. But it might also be, in some cases, there's a real problem. Dopamine cells in the substantia nigra have died. We're gonna need to make this change. We need to put a stimulating electrode in. Or if the hair cells in your ears all die, you can't hear. We now know why that is. They're not punished by God. They can't hear 'cause the little vibrations in the air that we can't see aren't getting into their brain. So, we take a cochlear implant. We take a microphone. We record the vibrations. We put it into the brain in the right way, and now many people can hear. That was a miracle not too long ago. Now it's a technology you can just go buy. And moving that progress of neuroscientists, some things like schizophrenia we've made very little progress. It's very hard to figure out what we would do, but at least we understand the nature of the disease. It's not that they've got a germ or a bacteria or a virus. It's not that their one gene is big and bad and broken. It's not contagious, but that there's some wiring challenges and that most days someone with schizophrenia is perfectly normal. Most people with neurological and psychiatric disorders spend large periods of time normal between periods of migraines or depression. They are acting totally reasonable, and we want to spend more time, push them more toward those times of health and satisfaction and reward, and away from those times of disability, engagement limitations. And I think we're moving in that direction instead of labeling and putting people off in homes, more to engaging, understanding, and then eventually intervening.

    2. AHAndrew Huberman1:02:08

       I agree that progress is happening fast, and, uh, while sometimes it might seem that we're not moving in the right direction, I think neuroscience, uh, in particular is striving very hard. I say in particular because other fields like immunology, um, in particular, and physics have experienced great advances, as, as you've pointed out before, over the previous 100 years. Whereas, you know, anytime there's been a, you know, pathogen that we've wanted to deal with and, and humans have put a lot of time and energy toward it, done a pretty good job of dealing with that pathogen. The same can't be said for, um, neurologic diseases like Alzheimer's. I mean, progress is coming, but it's been much more slow, and we don't have cures. We don't have cure solutions.

11. 1:02:51 – 1:09:45

    Learning, Reflection, Visualization, Testing

    1. AHAndrew Huberman1:02:51

       I want to get into the neuromodulators in, in some degree of depth as it relates to neuroplasticity and certainly the, um, incredible work that you're doing with devices, uh, vagal nerve stimulation and, and so forth for, uh, treatment of everything from PTSD to tinnitus to, uh, you have a beautiful paper that came out recently in Nature. Congratulations. We'll provide a link to that paper as well as some of the others relating to restoration of motor function for people that have restricted motor function for various reasons. Before I do that, I can't help but, um, raise once again this, uh, sort of mental model of plasticity that I'm trying to build out as we go along here, which, whereby, um, focus and friction seem to be, uh, prerequisites. I mentioned sleep. You added to that reflection, and I just really want to underscore that and certainly add it to this list that I'm building here, uh, because about six months ago I did an episode on how best to study and learn.

    2. MKDr. Michael Kilgard1:03:43

       Mm-hmm.

    3. AHAndrew Huberman1:03:44

       I went into the literature. I, I, I know what my study habits and tools are and what I've used over the years, um, but I, I went to the literature, the peer-reviewed literature, and, uh, there were a number of takeaways. But perhaps the most salient one was that students who self-test learn much faster and the information they learn is much more durable over time, they forget a lot less of it than any other method. Uh, so tests are not just a way for others to evaluate us, but for us to evaluate ourselves. Um, and it created a whole different picture of learning and memory for me because a, a simple statement made by a psychologist, not a neuroscientist w- was, um, when something like, you know, self-testing protects against, uh, it's anti-forgetting. And most of learning is just intervening in the forgetting process. Just like there are a number of stimuli in this particular interaction that unfortunately I will forget, or fortunately perhaps, the irrelevant stimuli I won't remember. And so, so much of what we learn is, uh, is really about what we don't forget. It might seem like a trivial distinction to kind of flip, flip it that way, but, um, self-testing being key, and I think this element of reflection and mental reh- mental rehearsal is so key. Um, I think, uh, again, I don't want to, uh, demonize social media, but I think that one of the downsides of smartphones and social media is that after we leave a lecture or a movie or a social interaction, in the past, prior to 2010 say, the tendency was to walk to one's car, drive home, maybe think about that interaction, think about what was good, think about what was bad, maybe let it kind of stew in us a bit. And now we tend to look at our phone and start getting additional stimuli that I think collides with and, and occludes the learning that would have occurred. So, we don't get a lot of opportunity for reflection. There's a lot of sensory input. Some of it's deprived, some of it's rich, but, um, there's not a lot of time for reflection. So reflection and self-testing as, um, kind of falling into the same bin and reinforcing learning and plasticity. The, the other one was that y- you talked about visualization and these skiers who, to avoid, uh, harming themselves, uh, they'd use visualization as opposed to just more and more runs down the slope. We've heard before, all of us, that, you know, when you imagine an experience, the brain doesn't know the difference between that experience and a real world experience. But of course, a real world experience includes other things. There's, you know, uh, vestibular feedback. There's...... gravity feedback (laughs) , you know, feedback with our relationship to gravity, to put it in common terms. There's all sorts of stuff, the wind in our ears and all. And you said, and I find this very interesting and very useful, that visualization and mental rehearsal can be useful for reinforcing things that we've already done in the real world, but it's probably not the best way to learn new things that we haven't done in the real world. So, um, we can pick any number of different examples, but I think people are smart enough to just leap to those on their own. So if, if they're trying to learn something and they're doing that in the real world, dancing, maybe it's a physical skill, maybe it's a cognitive skill, maybe it's an emotional skill, mental rehearsal is useful is what I'm, uh, I hear you saying, provided that you're rehearsing something that you actually did as opposed to just imagining something and expecting that you're going to be able to do that something. Do I have that right?

    4. MKDr. Michael Kilgard1:06:51

       Yeah. No. I think that's exactly right. I mean, if, if you know you're not gonna need it, biology would've said, "You don't need this." It's just a r- it's a, it's a leaf that's wiggling in th- air. I don't need to know where that leaf is. But this is the thing that cues me to where I'm gonna find my next meal. That's gonna be something I'm gonna be, uh, interested in. If this is gonna help me get a mate, I'm gonna learn that. If this is gonna be an irrelevant fact about a cloud, I'm not going to. And I think children have a lot of trouble with that. There's a stage in childhood where they, they'll see a plane up there and they'll say, "Oh my God, there's a little plane up there." That plane has no interaction with you at all, but they're fascinated by it. They're cued into it. They're interested in it. We, all the time, have to figure out what are the things we're gonna be tested on? What are the things you're going to need to know? And one of the ways you do that as educators, which we both do, is you give them tests. And a lot of people say, "I can't wait to have the last test." Really? You wanna have no more time when someone judges and determines, "How'd you do? What is your evaluation?" I think, a lot of times, many of us become lifelong learners, and we're comfortable knowing that someone else knows more than me. I'm not gonna win, but that I'll be able to find out how much did I do, that I know what's possible. Um, and testing is good for us. Uh, educators do it not just to assign and rank and distribute and give Bs and Cs and Ds, but so someone says, "You could do better than that. If you got a D, you could have done better." I'm not saying you're flawed. I'm saying you didn't put in whatever was needed. Now, maybe that person does need to put more work in to get the B or even the A, but it's not my opinion that they can't get it. It's that they didn't get it. Explaining what's real. What percent did you know? What did you actually learn? How good are you at throwing the tomahawk, at shooting the arrow, at doing rock climbing? The visualization I'm thinking about is, like, from Free Solo when he's imagining doing this. He's already done it, but he's now going through imagining it again. All of us do that. Uh, my children did, uh, martial arts, so they're both black belts in TaeKwonDo. And they would practice these forms. I took it at Berkeley when I was a student there, and I just really enjoyed it. Is it useful? I don't... I've never been in a street fight. (laughs) I've never needed to, to apply these skills, but there was a beauty to it. There was a usefulness to it, and someone came and tested me. I made it to yellow belt, full disclosure. Um, but I was gonna need to know it. And so I knew I would stand in front of other people and admit I didn't learn it. I wanted to learn it, but I didn't learn it. Knowing that someone, a mentor you respect, a peer you value, uh, a, a spouse who cares about you, whatever it is, is gonna look and see, "How'd you do?" I don't think that's harmful, judgmental, negative. It's not part of the culture of exceptionalism and meritocracy. That's just, "Give me some feedback, how am I doing." Uh, and a lot of times, we can do extraordinary things when people do raise the bar on us a little bit, uh, and that can be very self-fulfilling. Certainly, an over test-focused culture. My mom was a master, uh, uh, primary education educator. She didn't really care very much for all of the testing-focused stuff. She thought, "I've got to get this kid to learn how to interact well with others and put away his crayons. I don't need to worry about these particular flashcard-based

12. 1:09:45 – 1:18:05

    Experience Diversity & Time, Happiness, Life Appreciation

    1. MKDr. Michael Kilgard1:09:45

       skills." But we go back and forth with the times table. Is that really important, memorizing how multiplication works? Or should you spend your time with all the states, 50 states and all their state capitals? I don't have an answer. I'm not here to tell you that I know what the right thing (laughs) to do is. I don't know all the state capitals. My children do. Is that useful? I don't know whether that's gonna come out valuable, and that's one of the exciting things about life. You don't know what's gonna be helpful. Maybe playing a lot of video games is gonna turn out to be really helpful. I can't... have to have enough humility. I think certainly one of the things I know you've experienced as a scientist is just the incredible humility that comes from recognizing this thing is way more complicated than how I'm thinking about it. It just is. We start there. We know that, and we're okay with that. We make our best model, our best explanation of what we've got, the explanation that fits the data that we have now that's as simple as possible. And the reason we choose the simplest one is it's the easiest to prove wrong when it's inevitably wrong. And we just make this incremental progress. Life's a lot like that too. Uh, certainly parenting is a lot like that. I think this is gonna be good for the kid, and then, no, this is not good for the kid. I think this is gonna be bad for the kid. Oh, that turned out to be a really good learning experience, when they're in tears and there's, uh, some big crisis. Um, so understanding that we don't know it all, um, that things are typically neither as bad as they seem or as good as they seem, uh, and that maximizing something, that's kind of one of the key concepts I worry about a little bit, min maxima- min maximizing. Minimizing all the bad things, maximizing all the good things assumes you know which things are bad and should be minimized, which things are good and should be maximized. And a lot of times, we come to recognize later in life, oh, many of those things that I really worked hard not to have happen, those are really valuable experiences 'cause they taught me either how to interact with other people who've had those experiences or taught me some skill that I didn't know I would need to do, how to change a tire or whatever (laughs) else it is you don't want. Your tire to go flat, but then you learn how to change a tire. Now you learn how a scissor jack works or whatever thing that later comes in handy. So to me, it's more the diversity of experiences than the, um, better experiences. And I think right now, we're a little bit at a time where there's enough judgment about which experiences should you be having. Uh, I just returned from Yellowstone National Park, and there's a, a little platform you can look down on Grand Prismatic Spring. And there's people who are just like, "You are looking at a 700-foot-across hot spring on top of a super volcano with rings of different colors of thermophilic bacteria and algae." And you go-... take my picture and go." And it, it's just difficult to say, "Stop. Look at how big this is. It will take more time." So I assume that the time you put into it, this is back to your friction idea, the time you put into it is probably proportional to the impact, lasting impact it's going to have on your life. And so when you're checking boxes, looking for things, it's probably not gonna have much impact. When you're playing violin for the 100th hour, I'm not a violin player, but, uh, there's a point where you eventually have changed who you are, you're now a violinist. I'm a neuroscientist. I don't think it's something that's hard to do. Anyone can do it. Just spend all day doing experiments. And that's what's neat about reading books or being a skier or being a parent. Everybody can get good at it, but you only have so many hours. And so I always think about the pie chart. You only get 100%. Coaches always say 110%. There's no 110%. There's only 100%. How are you gonna spend your time? Here I'm talking about the waking hours, because I'm not going to cut corners on the sleeping hours. And so you just look, "How am I gonna spend it?" Some time spent working, paying the bills (laughs) , getting the job done, some time in leisure and recreation, some time with spiritual, um, activities, and trying to make that balance. I find it looks a lot like it looked for my grandparents. Like, the proportions of that pie chart do not look like, "I just want to disengage and spend all my time streaming on social media, just me personally." People who have done that look a lot like you'd think someone who's addicted would look. They eventually realize, "It's just not doing it for me anymore. I don't get much satisfaction." Um, Gilbert Harvey did this great experiment looking at what made people happy, had these little things pop up, you may know about this experiment, and ask, "How are you feeling?" And like, people were happy when they were getting eggs. It was just like, "I'm at the store. My wife said get eggs. I'm getting eggs." "How are you doing?" "I'm pretty good. I got eggs." That idea that you're happiest when you're accomplishing some simple goal, not some Olympic-level impossible goal, but just some simple thing that needs to be done. What was surprising from that study was that when people were daydreaming, which for years we thought the pursuit of happiness, our forefathers thought if you could just sit and contemplate your navel and, you know, have the, uh, examined life, you'd be most happy. Not so. Oftentimes contemplating our own life leads us to find someone who's got a better version of it, leads us to realize we're not accomplishing every goal. Uh, and so maybe humans evolved, were created so that they would be actively engaged in doing something. That appears to be the case. And when we disengage, it appears that things happen that are not good. What are those? Typically, in psychiatry they're called anxiety and depression. They're different things, but they may be very similar sides of a coin where this is not working for me, um, and I think we can work back to how about we go do the laundry? How about we go to the grocery store and find out that that is in fact a satisfying activity, even though it's pedestrian, it's not something you're going to put an Instagram post on. You know, making a good, uh, pancakes, I'm pretty good at making pancakes. I flip it over, it's just brown all along, I go, "That's a good pancake." Some people are not as good as me. I take a little pride in that. But I'm not beating them. I'm not better at pancake making. I flip it over and go, "It's a pancake." I serve it to the kid, the kid goes, "Good pancake, Dad." You're sort of done. I think we devalue that by thinking I could just go to, you know, International House of Pancake and they make a better pancake. That, I did it myself, a lot of people during COVID found out, making it yourself. I'd never made a bagel in my life, and suddenly we're locked down for two whole weeks (laughs) and it's like, "Let's go make bagels, kids." And I went and made a bagel. It wasn't a good bagel. I can make a, get a better bagel any place. But I made that bagel. I learned a little bit about it and I appreciate better those people who master that. And now when I taste a bagel, I go, "Now I see why your bagel's better than my bagel." Um, and so I think those experiences are all coming into my brain. I still remember, obviously I wouldn't have mentioned it, this thing six years ago, when I'm sitting in my kitchen with my kids and a pot of water and some flour trying to figure out what I'm gonna do with myself, I didn't want the whole world shut down. But I got that gift from it, that I have that better appreciation now of bagels. And I just think that's a, a world view that we really could've gone down a path where studying the brain made us unimportant. It made computers good and humans bad. I've not seen that at all. I'm super proud of all my friends. I don't, wouldn't rather hang out with a, a chat bot than with my friends. Uh, and I think that's gonna continue to happen. I don't expect, uh, there's gonna be a major revolution in that. And that's a surprise. It's a surprise that discovery keeps leading to good things, not bad things. Uh, and there are a lot of dangerous things, I mentioned machine guns and nuclear war- weapons, but we mostly haven't used those things. We've made all this good stuff. So you can see I'm an optimist, and it partly comes from studying the brain. I get to study the brain while it's alive and listen to neurons while they're actually firing. Other people looked at it while it was in dead tissue under a microscope, but they were both able to see this thing is alive, and that was reflective of how I feel as a live person. Not as a machine, not as a pawn, not as a, a, you know, um, one vote in a democracy, but as a real person. Uh, and neuroscience is supporting that. And that's been the history of science. We didn't ruin things when we found out that the sun's not revolving around us. (laughs) It made it better when we found out we're revolving around the sun. We're not the only galaxy. All those things were good for us. But at first people were really nervous about having the answer. I've just been surprised that finding the answer keeps being the good thing. You'd rather have the answer. There are no answers we don't want. That's really surprising to me, because it could have turned out we're all bad and there's nothing here and all the nihilist philosophies and all the rest would be right. But that doesn't appear to be the case. Um, and all that comes from this sort of friction, this reflection, all these issues, learning about how the brain works, all the way down to the biological level, all the way up to societies and groups of people who continue to be mostly pro-social, (laughs) mostly taking care of each other, mostly not destroying the Earth, figuring things out, making adjustments. The ozone layer had a hole in it, we made some changes. That seems very reasonable. We may not be fast about it all the time, but we tend to make the right path, both in science as well in our species. And I think that's because they're both using the same mechanism. We get feedback from the world. When we make the wrong choices, we see it. That's true as a parent, true as a scientist. When things don't work, you're gonna find out. Um, and I like that feedback from the world.

13. 1:18:05 – 1:19:53

    Sponsor: Function

    1. MKDr. Michael Kilgard1:18:06

Episode duration: 3:09:35