Dr. Charan Ranganath: How to Improve Memory & Focus Using Science Protocols

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. Charan Ranganath. Dr. Charan Ranganath is a Professor of Psychology and Neuroscience at the University of California, Davis. He is one of the world's leading researchers in the topic of human memory. And memory, of course, is an essential component to our entire lives. Memory isn't just important for remembering things that we learn, it's also vitally important for setting the context of our entire life. Meaning, only by understanding where we come from, who we were and who we are currently can we frame what we want to do in the next moments, the next day, the next years, and indeed for the rest of our life. This is why, for instance, that people who have deficits in memory, either due to brain damage or due to age related cognitive decline or diseases like alzh, Alzheimer's dementia, suffer so much not just in terms of not being able to remember things for sake of daily tasks, but also for sake of placing themselves in the larger context of their life. Recognizing family members isn't just about being able to relate to those family members on a day to day basis. It's also about understanding the full context of all one's memories with those people and what meaning a given interaction brings to any of life's experiences. So today you're going to learn how memory works. You're going to learn about things like deja vu, you're going to learn ways to offset age related cognitive decline, what the research really says about that, and ways to prevent things like Alzheimer's dementia. We also talk about ADHD or Attention Deficit hyperactivity disorder, and Dr. Ranganath shares his own experience with ADHD, how it relates to memory, and the tools that he has used in order to combat his own ADHD. Dr. Ranganath has an exquisite ability to describe research studies in clear terms and to combine that with his own narrative and life experience in a way that really frames for you practical tools that you can apply in your daily life. Before you 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, I'd like to thank the sponsors of today's podcast. Our first sponsor is David. David makes a protein bar Unlike Any other, it has 28 grams of protein, only 150 calories and 0 grams of sugar. That's right, 28 grams of protein and 75% of its calories come from protein. This is 50% higher than the next closest protein bar. These bars from David also taste incredible. My favorite bar is the cake flavored one. Then again, I also like the chocolate flavored one and I like the berry flavored one. Basically, I like all the flavors. They're all incredibly delicious. Now for me personally, I try to get most of my calories from whole foods. However, when I'm in a rush or I'm away from home or I'm just looking for a quick afternoon snack, I often find that I'm looking for a high quality protein source. And with David, I'm able to get 28 grams of high quality protein with the calories of a snack, which makes it very easy to hit my protein goals of one gram of protein per pound of body weight. And it allows me to do so without taking on an excess of calories. Again, again. I focus on getting most of my food from whole food sources throughout the day. But I typically eat a David Bar in the late afternoon when I get hungry between lunch and dinner. Sometimes also mid morning if I get hungry then and sometimes I'll use it as a meal replacement. Although not a complete meal replacement, it can get me to the next meal. So if I need to eat in a couple of hours but I'm really hungry, I'll eat a David Barr. As I mentioned before, they are incredibly delicious. In fact, they're surprisingly delicious. Even the consistency is great. It's more like a cookie consistency, kind of a chewy cookie consistency, which is unlike other bars which I tend to kind of saturate on. I was never, never a big fan of bars until I discovered David bars. If you give them a try, you'll know what I mean. So if you'd like to try David, you can go to davidprotein.com huberman Again, the link is davidprotein.com huberman Today's episode is also brought to us by Levels. Levels is a program that lets you see how different foods affect your health by giving you real time feedback on your diet using a continuous glucose monitor. Now, one of the most important factors in both your short and long term health and your energy levels each day is your body's ability to manage blood glucose. To maintain energy and focus throughout the day, you want to keep your blood glucose level steady without big spikes or crashes. I first started using Levels about three years ago as a way to understand how different foods impacted my blood glucose levels. And it's proven incredibly informative for determining what food choices I make, when best to time my food intake around things like workouts, both cardiovascular training versus resistance training and when and what to eat, close to sleep or not so close to sleep when I wake up in the morning, if I'm fasting or breaking a fast, et cetera. Indeed, using Levels has helped me shape my entire schedule so I have more energy, more cognitive focus, my workouts are better, my sleep is better, everything got better when I understood how different things, especially food, were impacting my blood glucose levels. So if you're interested in learning more about levels and trying a CGM yourself, you can go to Levels Link Huberman Right now, Levels is also offering an additional two free months of membership. Again, that's Levels Link L I N K Slash Huberman to try their new sensor and two free months of membership. Today's episode is also brought to us by Waking Up. Waking up is a meditation app that offers hundreds of guided meditation programs, mindfulness trainings, yoga, NIDRA sessions and more. I started practicing meditation when I was about 15 years old and it made a profound impact on my life. And by now there are thousands of quality peer reviewed studies that emphasize how useful mindfulness meditation can be for improving our focus, managing stress and anxiety, improving our mood, and and much more. In recent years I started using the Waking up app for my meditations because I find it to be a terrific resource for allowing me to really be consistent with my meditation practice. Many people start a meditation practice and experience some benefits, but many people also have challenges keeping up with that practice. What I and so many other people love about the Waking up app is that it has a lot of different meditations to choose from and those meditations are of different durations. So it makes it very easy to keep up with your meditation practice. Both from the perspective of novelty. You never get tired of those meditations. There's always something new to explore and to learn about yourself and about the effectiveness of meditation, and you can always fit meditation into your schedule, even if you only have two or three minutes per day in which to meditate. If you'd like to try the Waking up app, please go to wakingup.comhuberman where you can access a free 30 day trial. Again, that's wakingup.comhuberman to access a free 30 day trial. And now for my discussion with Dr. Charan Ranganath. Dr. Charan Ranganath, welcome. Thank you Speaking of memory, we go way back.

We do, we do.

I was a graduate student when you were first hired as an assistant professor, which for those that aren't familiar with the academic nomenclature and trajectories, assistant professors are professors that have not yet received tenure. But now, of course, you're a full professor and you are a world expert in memory. Something that I think occupies the minds of all of us, even if we're not trying. So that's actually the segue to my first question, which is, as we move through our day, how much of our cognition, our perception is focused on things that are happening in the present as opposed to being driven by prior memories? You know, studies ever been done that evaluate how often our brain switches to thoughts about the past? Of course we learn about things that are in our present. I know this is a cup because I was taught that at some point, but what I'm referring to is how much of our thinking on a day to day basis is literally in the past.

Well, it's interesting that. I mean, it's. First of all, it's a great question to start off with. And it's interesting because I actually don't think memory is about the past. I think memory is about the present and the future. It's about taking selectively what you need from the past to make sense of the present and to project to the future. I know you're a vision guy, right? And so if you look at people's just eye movements, right. The first time I came into this room, I'm sure I wasn't aware of it, but I'm sure my eyes were going all over the place. Now if I came back to visit, you say if you're like, oh, that was an awesome interview, or whatever, right? Hopefully, but maybe not. But let's say I do, right?

Chances are, yeah.

So I go, and my eyes will probably go right to the Rick Rubin photo. Then I'll go right to something else, to the espresso machine. And so my memory allows me to make predictions about where things are. And it's almost preconscious so that it's happening without our awareness. And it's like confirmatory. We're grabbing the important stuff and making sure everything's where it's supposed to be. And you can see this play out in phenomena also, like change blindness. That's a little bit of a different phenomena. But basically in change blindness, there's a famous example where they show a video of people playing basketball and they're passing the ball back and forth and Then this guy in a gorilla costume just walks behind them and about, I think it's 40% of the people who watch this video don't see the gorilla. And the reason is, is that you're generating these serious expectations about what's in front of you. And so you're not literally seeing what's in front of you. You are creating an internal model, a simulation really, of what the outside world is. And memory, whether it's semantic memory, which we'll talk about, I'm sure, your knowledge about the world, like the cup thing. If it's episodic memory, which is your memory of what happened, let's say, just a minute ago, it's all coming into play. In terms of your sense of where you are, right. If I just ask you what day is it? You will use episodic memory for that? Tomorrow morning I'm going to wake up in a hotel room. If I don't have episodic memory, I will freak out because I'll be like, where am I? Did I get kidnapped? Why am I here? And that's really the experience of people with memory disorders. I mean, they have to be in really familiar environments because it's frightening otherwise. Right. So even I wouldn't necessarily say that we were never seeing the present. Of course we are. Right. But our understanding of the present is so informed by the past that it allows us both to focus on what's important, what's non redundant with what we already know. And it also allows us to detect surprises and find out the things that are unexpected and grab the most informative stuff as well.

Yesterday I took a brief nap. In the afternoon I do this practice of non sleep, deep rest.

Oh yeah? Yeah.

In the afternoon.

I gotta have you teach this to me sometime.

Yeah, it's very restorative for mental and physical energy, I find. But I fell asleep toward the end of it and when I woke up I was in a dark room, but I didn't know where I was for about, felt like 10, 15 seconds. Somewhat scary, but I'd forgotten that I was in my solo studio. I had turned the room lights down. What is it? When we have these lapses of memory as we emerge from sleep, or sometimes if one has been severely jet lagged, you can experience this disorientation of place. Do we know what that is?

Well, a lot of your sense of where you are comes from episodic memory. Now there's a school of thought that says that episodic memory, which is your ability to remember past events, comes from your Ability to understand where you are. And we have some interesting data from sea lions, actually, that speaks to this issue.

Sea lions.

Sea lions.

Okay, we'll get back to that.

We'll get back to the sea lions. But I would argue that to remember where you are when you first get up, you have to engage in an active episodic memory retrieval. That is, you have to figure out, well, how did I get here? And that takes a moment. Orienting yourself takes a moment. And that because it's. It's a little bit of a controlled memory search, right. It's not something that's in front of you that reminds you of where you are initially. And you're also in this little bit of a fog when you wake up. I don't know enough about sleep to say, but I would suspect that people probably are in some kind of a stage one ish, or just high alpha. These brain waves that are like, very much associated with kind of grogginess as you're getting up. Neuromodulators are probably super low. So you're, you know, so basically not.

Much epinephrine, not much adrenaline.

Yeah, yeah, exactly. And so that's going to lead you to really be slow in doing that memory retrieval that you need to orient yourself. So, like in the clinic, if you want to ask. If you want to understand whether someone has a memory disorder, one of the simplest things is to ask them, what day of the week is it? What month is it?

Who's the president?

Who's the president? Yeah, right. Now, that's a loaded question.

It depends on what time of year relative. Relative to the election you ask. Right? Yeah, very interesting. I'm curious also why it is that most all of us have a stable representation of who we are. So my understanding is that even people with very severe memory deficits don't wake up in the morning and wonder, who am I? Or who is this person in this body that somehow we remember that we have a self, that we are separate from other selves, we. That that kind of knowledge might be innate, we might be born with it, and that the representation of self in memory is very stable. Is that true?

Well, here's what I'll say. It's a really interesting and complex question. Everything's. You always talk to a scientist. It's complicated. But I'll give you as simple of a thing as I can, which is, so if you look at patients with amnesia, so they have a memory disorder where they can't form new memories, they have a sense of who they are. As you mentioned. Right. It's not like they don't know who they are. And I mean, like, they know their names, they know their biographies and so forth. But what happens is, at the time, let's say if you had gone swimming and you nearly drowned, you had a hypoxia incident or a cardiac arrest, or, you know, you had, like a traumatic brain injury, severe memory deficit, right? Your sense of self doesn't update. It gets kind of stuck. And so there is kind of a sense of looking and not expecting yourself to be as old as you used to be as you are, because, like, you're. You're stuck in your sense of who you were. And I do think I talked. My good friend Rick Robins at Davis is a personality psychologist, and he studies the development of personality. And it does develop. You know, it kind of stabilizes in these adolescent years. And that's actually also interestingly related to memory. But it does change. People do change in really interesting ways. So one thing is that people grow more optimistic, on average, as they get older. Is that right? Yeah. Yeah, that's true. So Laura Carstenson, your colleague at Stanford, actually, has done some really cool work on that topic.

They become more optimistic, and yet I would argue that we become more set in our ways because neuroplasticity, the ability to reshape our neural circuits, diminishes with age.

Well, you know, so I think that's overdone a little bit. I think you're right. You know, you definitely see less dopamine activity, for instance, as people get older. And. But what I'll say is that people have gobs. If you have a healthy aging person, they have gobs of neuroplasticity. But often what happens is, yeah, you get stuck in your ways. And that could be related to a few things. One is that you get changes in the prefrontal cortex, and that leads you to be less cognitively flexible. It can be also because people just build up so much prior knowledge about the world that it just becomes kind of ingrained that this is the way it is, and it's harder to be surprised. I mean, you kind of see this with old scientists, right? They go like, nothing's new. Everything's been discovered in 1960, and nothing new has happened since.

And by the way, for folks listening who are considering a career in science, nothing could be further from the truth. In fact, prior to recording, you told me a saying that I've never heard before. I don't know if it's cynical or optimistic, but if I Recall the quote that Dr. Ranganath passed along, which does not come from him, it descends from somebody else, not to be named is that quote, science progresses one funeral at a time. Very, very, actually very interesting statement. It could be examined from a number of directions. But I agree, I agree. I mean, there's some wonderful, let's call them aged scientists with tremendous knowledge and excitement. I mean, one only has to listen to like the Nobel Prize winner Richard Axel talk about his love of olfaction and perception and you can sense his delight and he's getting up there. Sorry, Richard, but it's true. You're in your. He's in his 70s, right? Hopefully he'll live a very long time, but. And certainly science progressed as a consequence of him being alive. And we're working on the olfactory system. But I think what you're referring to is really important. Neuroplasticity doesn't necessarily shut down as we age. It might even stay open to the same degree as early adulthood. But if I understand what you're saying correctly, you believe that it's because people tend to seek out less new knowledge as opposed to lacking the ability to, to create new knowledge.

I believe that's true, but that's kind of, that's an opinion. I don't have data on that per se, but someone's probably looked at this. But that would be my sense is, is that a lot of what happens with the way people's lives play out as they get older have to do with their environment and their experience? And that's not to say that. I mean, yes, neuroplasticity does change as you get older, but it doesn't account for the degree to which sometimes people can get stuck and set in their ways. And you know, your example of the scientists is such a beautiful example because I look at the scientists who don't get stuck in their ways, right? And they constantly challenge their beliefs. They surround themselves with a diverse group of people who stimulate them and they're also open to prediction error, that is, they're open to saying something could be violating my knowledge of the world or my understanding of the way world works. So here's just an example and this is. I know I'm going to be free associating all over the place. We can get into that. But it's like one of the coolest studies that we ever did and I totally credit my postdoc Matthias Gruber for this. He came into my lab, originally German, came in from University College London, and he told me he wanted to Study curiosity and its effect on memory. I'm like, this is just. I am being totally closed minded. I said, this is just a dumb topic. You know, it's. Everybody knows if you're curious about something, you'll remember it better just because you're interested, right? So he said, no, no, no, this is really interesting. And so he did this experiment and I got on board with it. I, you know, we really kind of collectively. It was just this beautiful thing where I was exposed to something new and I got excited about it. And so the idea was we would give people these trivia questions. And so it's kind of like a pub quiz, right? You sit in a pub quiz, sometimes you get a question and it's like, I don't know the answer. Sometimes you get it, you know, I know it. Sometimes you go, I don't know, but God, I really need to know the answer to this. And you get this itch, right? Or sometimes your listeners, I mean, they're probably very curious people. That's why they listen to this. And maybe some of them go to your show notes afterwards because they want to learn more, right? So we actually scan people's brains using functional mri. And so we scan them when they get questions. And sometimes they had said, I'm really curious to find out the answer to these questions. Sometimes they weren't curious. And then we make them wait about eight seconds and then, or 10 seconds, I think it was something like that. And then we show them the answer. So they're kind of in suspense, kind of like you're watching like Breaking Bad or something back in the day, people at commercials. And so you're like, oh, no, I got to find out what's going to happen to Walt. So you're in suspense. You need to know the answer to this or you don't care. Sometimes you just don't care. You're just sitting around. So we show a little face and we say, hey, how likely is it you think this person knows the answer to the question? Now this is a totally dumb thing to do because they don't know this person. They're just looking at a face. They're just making some arbitrary decision. But I'll get to why we did that, because that was, I think, the coolest part of the experiment. Well, let's first get back to the trivia question. So we found that when we looked at brain activity, when we give people the question right afterwards, there is a burst of activity throughout the so called reward circuit of the brain. There's a series, it's not really a reward circuit, as we've discussed offline. It's really these areas of the brain that process the neurotransmitter dopamine. And unlike many other neuromodulators, this go all over the place. Dopamine is much more restricted in its effect. And so in the midbrain near the ventral tegmental area. Sorry, I'm geeking out on this.

No, we've talked about that in this podcast. There's a particular. I think the key statement that you made that people should hold on to as we progress through this is that dopamine is not dumped everywhere. It's not sprinklered all over the brain. It's released in fairly restricted sites in order to drive particular processes. I think that's sufficient for now.

Yeah, yeah. And so when we look at functional mri, we can't measure dopamine, but what we see is activity in the dopaminergic midbrain area, meaning the area of the brain around the midbrain. And you see it in the nucleus accumbens, or what's called the ventral striatum, which is another area that's super high dopamine reward processing area. The more curious people are, like, on a one to six scale, the more activity you see. It's just like this beautiful relationship, right? And it's not driven by the answer. Now, there's a reason we probably didn't get it for the answer, but it's driven by the question. So it's not like they're like, oh, I learned something new. It's like, I want to get this knowledge. And so that's part one of the story. Part two of the story is we show that face right after the question. And if people are curious to find the answer to the question, they get a bump in memory for the faces relative if they're not curious. Now, the faces have nothing to do with the trivia question, but it's being in that curious state that drives this dopaminergic activity in the midbrain. So there's a whole lot of other studies, findings from that study. But basically, I think, God, I got to. You know how sometimes you do a lot of studies. I mean, I published like 180 studies. So it's like I'm trying to remember the exact. I think it was like, functional connectivity between the hippocampus and the red brain during the face was predicting better memory for these faces in general. Something like that.

We can put a link to the paper, of course, in the show note captcha. So let me make sure I understand that the. When people are prompted with a question that drives release of dopamine, the amount of dopamine is proportional to how curious they are to get the answer to that particular question. And then the dopamine itself, if elevated because they are very curious, can increase the probability that they will remember the answer. It creates a milieu, an environment for better memory. But that can confuse us and make us think that dopamine improves our memory. But it's that curiosity increases dopamine, which increases the capacity to store information that comes subsequent to curiosity.

Beautiful synopsis, but I'll do two cheerful amendments. So one is, technically, we're not measuring dopamine, so I have to be very clear about that. This is bold signal, meaning it's, you know, metabolic activity, but it's following all the usual suspects of where you'd expect it to be. The second thing is, I do think that dopamine is playing a part. And, I mean, it definitely facilitates plasticity. So I do think it helps in learning the answer, for sure. And there's a whole theory called synaptic tagging, which basically says that if you just release a bunch of dopamine and then you have these potentiated synapses, that you can drive plasticity in those synapses, even if it's not happening at the same time. But what's really cool is the face has nothing to do with the trivia question. The theory that we have is when you get that bump in dopamine activity, you're motivated, you're energized to get the answer, and you're driven towards a state of plasticity. And now I've given you something that has nothing to do with this question, and boom, you got it.

You know, so when people ask me, and they ask me a lot.

Yes.

How best to elevate their brain dopamine. One reasonable answer based on this study is curiosity. To engage curiosity. Do you know the quote by Dorothy Parker? The cure for boredom is curiosity. There is no cure for curiosity. I believe it was Dorothy Parker.

I love that.

If it wasn't, I'm sure we'll find out quickly in the. In the comments on YouTube.

Older people show the effect just as much as younger people do. Kids show it just as much as older people do. It's just something that sticks around. So, I mean, speaking to your point, if you are surrounding yourself with things that will stimulate your curiosity, and if you're open to that curiosity, we could talk about knowledge gaps. And all these things that stimulate curiosity, novelty is another one. Richard Morris has some beautiful data on this with rats, but Emera Dussel and I, too, have some data with humans. Surprise. All of these things. I have a whole chapter in my book on this drive, that system.

So the dopamine system.

The dopamine system. So basically, if you expose yourself to opportunities to be proven wrong, you expose yourself to new people, places, situations, and you allow yourself to be energized by these things and not be scared and anxious, not be like, oh, this person's saying something that I disagree with. I can't deal with this, you know, or, oh, we figured this out 30 years ago. We don't need. Nothing's new here. If you can be open to that, I would argue that you're going to be engaging lots of plasticity, and that's something that's preserved in old age.

Recently, we had one of the world's experts on romantic relationships on this podcast, Esther Perel, to be specific. And we talked about a lot of things related to romantic relationships. But she said that one of the most sustaining factors for romantic relationships over long periods of time is a sense of curiosity, both about the other person, but also about oneself and how one changes in the context of the relationship, and also curiosity about where the relationship could eventually go were one to continue to invest in it. So this word of curiosity seems to be a resounding theme I'm struck by. Although it makes total sense that curiosity would drive dopamine release in these pathways, that novelty would drive dopamine release in these pathways, and that also in the physical realm, dopamine is so important for physical movement.

Yes.

I don't think this is a coincidence. Right. Somehow evolution organized this neuromodulator dopamine, to be involved. The way I think about it is in both a physical movement, it's required for it, in fact, as well as cognitive movement. What we're really talking about is cognitive forward movement, if there is such a thing. Is there a. We're both neuroscientists, but you're the memory researcher. Is there. Is there sort of a word or a framework for thinking about cognitive movement, forward meaning, as opposed to just recycling past ideas and memories? The notion of taking memories and actually putting them, as you said earlier, into the present to anticipate the future, actually forward mental movement?

Huh. That's a really interesting question. Well, first of all, I want to be careful and not to say dopamine does this because it's going to. You're. It's a trap, right?

Well, to be clear, you observed heightened activity in a. In a dopaminergic circuit. So the idea that it would not involve dopamine is a bit of a stretch. But you didn't directly show that it was dopamine.

Yeah, I wouldn't be exact. And just say that assigning a single function to a chemical is, you know, risky. But that said, I do believe there's a link. One of the things that you see is in Parkinson's disease, dopaminergic neurotransmitter mission is shot. And depression is also a symptom of Parkinson's disease. It's quite a severe one, in fact. And so what I think, one theory goes is that dopamine energizes us to seek rewards or to seek information. Right. So a big part of movement is you move to get something. It's approach. Right. They talk about approach and avoidance as basic kind of things that you want to program. And so a person with Parkinson's disease has a problem with willful movement, tremors and stuff, too. But I think that dopamine is involved in this kind of energizing you to move. I think it's involved in energizing you to seek information. I think it's involved in energizing you to seek rewards. And so I do think there's some kind of a common pathway there and speaks to this issue of the difference which you've talked about, and I talk about a lot as wanting versus liking. And so Kent Berridge at Michigan has a great work on those gobs and gobs of manipulations of dopamine activity. And what he finds is an animal, let's say, that is deprived of dopamine, it will go for rewards just fine. It just won't work for them. It won't do the work that you need to get a reward. But if you just put it in front of them, they'll take it. So what dopamine, it is heavily involved with these opioid systems that does drive reward responses, and it's heavily involved in learning about rewards. And that's why you get a big dopaminergic bump when an animal gets a reward, because you're learning about the reward and what predicted the reward. There's a little bit of a credit assignment process that takes place. What's interesting is you get this too with, actually, my colleague at Davis, Brian Wilchen, some beautiful work where he's looked at trace conditioning, which is when you have like a. Let's say if you play a tone and you wait a long time, and then the animal gets a shock. Right. And so what you find is that the animal learns to be afraid of the tone. But it's such a long time in his thing. I think it's on the order of 10 seconds or above. The animal has to be somehow doing something to be able to blame that tone for getting shocked. Right. And so what he found was that there's this burst of dopamine activity in the locus coeruleus, which is actually known for norepinephrine. But there's really cool work on dopamine in the LC now modulating hepatitis hippocampus. Sorry to get all nerdy here, but.

No, no, trust me, this audience likes nerdy.

Okay.

I think that's why part of why they're listening. A locus coeruleus is just a area of the. Of the brain that tends to sprinkler large brain areas with epinephrine, which is. Or norepinephrine, noradrenaline for alertness. So somewhat distinct from the dopamine system. But you're telling us it can also release dopamine.

Yes, that's right. And sometimes they co. Release from the same neurons, from what I understand. And so what seems to be happening is. And he's studying this now, but what seems to be happening is it's not that the animal's going, oh, I just heard a tone. I heard a tone. And then they get shocked. It may be more like they get a shock, and then they get an immediate what just happened? And then they get a memory retrieval of the tone, and that allows them to put the two together to learn that this tone caused the shock. Right. And dopamine seems to be playing a part in that learning process too. So it's not just about reward. It's really kind of, you know, the next time you hear that tone, you might. If it were a real threat, you could actually escape from it. Right. And there's this whole active avoidance literature that you can look at with these approach circuits. They're actually quite useful for avoiding threats and avoiding punishment. So it's really. To me, I see this role for energizing, and that's often rewards. I mean, you know, I like rewards as much as the next. I mean, look at how much coffee I drank when I got here. So it's not that, but it's just that it's mobilizing you.

I think I'd like to take a quick break and acknowledge our sponsor, AG1. By now, many of you have heard me say that if I could take just one supplement, that supplement would be AG1. The reason for that is AG1 is the highest quality and most complete of the foundational nutritional supplements available. What that means is that it contains not just vitamins and minerals, but also probiotics, prebiotics, adaptogens to cover any gaps you may have in your diet and provide support for a demanding life. For me, even if I eat mostly whole foods and minimally processed foods, which I do for most of my food intake, it's very difficult for me to get enough fruits and vegetables, vitamins and minerals, micronutrients and adaptogens from food alone. For that reason, I've been taking AG1 daily since 2012 and often twice a day, once in the morning or mid morning and again in the afternoon or evening. When I do that, it clearly bolsters my energy, my immune system and my gut microbiome. These are all critical to brain function, mood, physical performance, and much more. If you'd like to try AG1, you can go to drinkag1.comhuberman to claim their special offer. Right now they're giving away five free travel packs plus a year supply of vitamin D3K2. Again, that's drinkag1.com Huberman to claim that special offer One thing that we talked about just briefly earlier was this non sleep deep rest protocol that in yoga tradition is called Yoga Nidra or yoga sleep because you lie down, it's self directed relaxation, long exhale breathing to slow your heart rate, etc. Etc. I called it NSDR not to appropriate it, but because the language of Yoga nidra is a little bit of a separator for people. It sounds a little bit esoteric and non sleep deep breaths tells you what it is, right? There's a study out of the University of Copenhagen. I can provide a link to it in the show. Note captions and I'd love your thoughts on it that show that people who do this practice. This is a PET imaging study, so positron emission tomography for those that don't know and they see significant increases in striatal dopamine in the condition of people that do this self directed relaxation as opposed to a more traditional meditation. And this is why I say that NSDR is useful for restoring mental and physical vigor which translates to this idea that dopamine prepares us for or is a reservoir for potential movement typically toward rewards. And I love that we're talking about some of the other facets of dopamine because all too Often people think about it as pleasure or motivation, and certainly it's involved in motivation, and I'm very happy to learn that it's also involved in learning. I think, seriously, that's a novel perspective on dopamine, and we hear so much about dopamine. Do you think that when dopamine is released as a consequence of curiosity in a way that primes the memory system, that we become entrenched in particular behaviors or routes of pursuing curiosity to the exclusion of others? What I'm thinking about here, as a kid, we've seen these data. Kids with ADHD actually have terrific ability to focus if it's something that they're really excited about, really curious about. So you give a kid with ADHD who loves video games a video game, and they're like a laser.

Yeah.

So it's not that they lack the capacity to focus, it's that they have a harder time dropping into focus. But it seems that because of the learning dimension to dopamine, that these circuits could potentially, quote, unquote, learn that it's video games that provides that feeling of focus to the exclusion of other things. Meaning how does one keep a diversification of inputs to the dopamine system so that we're continually driving dopamine through lots of different things as opposed to just social media or just video games or just pick your favorite thing? Because becoming a functional human being involves the requirement to focus on many things, not just the things we were curious about.

Yeah, yeah, yeah. I mean, to me, I talk about this a little bit in the book, but to me, and if you look at the literature, too, you can see this. A big part of being curious is the appraisal process, so to speak. And what I mean by that is saying something happens, right? Let's say something in your environment happens. If you're gonna. You have a decision to make. Is this interesting? Is this important? Is this scary? And I think the thing is, is that you need to be open to that possibility that it's interesting. So, like. So let me just give you, like, an example that I. That I often give. Let's say you're walking in a neighborhood, you're traveling like you do for many of your events, and you walk into a new neighborhood you haven't been to. It's nighttime, kind of poorly lit, and you hear a loud noise, right? You could be like, well, that's a gunshot. I better hide or I better run. Or you could be like, oh, maybe there's a club nearby and there's like a cool band. Playing I should go check this out. That appraisal is really critical for how you respond. And so it's not just a matter of curiosity happens. It's a process of cultivation and it's a process of appraisal. And so, I mean, this is, I think, you know, I'm not a wellness guru or anything, but it's like, I think this is one of the cool things about mindfulness training is it forces you to take the mundane and be curious about it. And when you start paying attention to your breathing, my friend Mishi Ja really kind of turned me onto this. She wrote a book on mindfulness and meditation. And one of the things that happens is you're breathing. You realize, wait a minute, this one isn't the same as the last one, right? Or you can do these meditations. I'm sure you've done this right? This part of like this sound is different. I'll sit in the backyard doing, thanks to you, I do this morning, 10 minute thing. And so I'll be out in the backyard and I'll be like hearing some sound. And I'll be like, oh, that sound. There's a bird there. I didn't even notice that, you know, and then there's some other sound I'm hearing the freeway. That's annoying, but I heard it. And so these. It's really a matter of paying attention in some ways and being open to it. And I think this speaks back to this thing about as you get older, sometimes people find it scary to be in a new place. People find it scary to meet a person who's different from them or so forth. I mean, I love listening to music that's a little bit out of my comfort zone. Some people hate it, you know, So I think some of it is sort of cultivating, being comfortable with discomfort.

It's such an important theme. I feel like nowadays, in part because of the algorithms on social media, we're. We are fed things that feed our progressively greater and greater scrolling and dwell time, as it's called. You know, the algorithms are measuring clearly how long we dwell on a given image and what's in that image and et cetera. But it'd be nice to cultivate an algorithm for curiosity. Surely it can be done. I mean, you got all these smart computer scientists and AI folks, and we come into this world naturally curious. All primates, including humans, will visually fixate on anything that's novel, right? And study it and try and make predictions and gain understanding. Maybe now would be a good time for us to discuss A little bit about the circuitry involved in memory, so that we have that as a template to digest some other themes in memory. Most people are probably familiar with the so called hippocampus, which means seahorse. Looks a little bit like a seahorse. Although the anatomist had a little bit of an imagination there, in my opinion. But hippocampus, let's add to it prefrontal cortex, which you've already mentioned, and then these neuromodulatory systems. So if we were going to assign a one sentence definition, functional definition to each of those areas, what would you say the hippocampus does?

A lot of other neocortical areas, please.

And let's add those in. But I think if you can start with three, I think then folks can digest.

The hippocampus is controversial. I mean, it's the most studied area of the brain arguably, except for maybe V1.

Visual cortex.

V1, yeah. But I believe, and my colleagues do. I wrote a big paper with Howard Eichenbaum, the late Howard Eichenbaum and Andy o' Linas on this, who, you know, from Davis. And we believe that it's about linking various experiences to a context. And what I mean by that is you've got information about smell, high level vision, high level semantic knowledge information. Right. And the hippocampus is. Wiring is really set up to not understand what's going on. So the late David Marr, who's pioneer in computational neuroscience, proposed that what the hippocampus is about is what he called simple memory. It's basically saying, I know Andy Huberman. Sorry, okay.

He used to call me Andy. That's fine. Yeah, long story.

It's a Davis thing you would understand. So. So I know Andy Huberman. Right. But to have a memory of this moment that's separate from, let's say I saw you at some neuroscience retreat when we were in. When you were in grad school. I have to have some part of the brain that doesn't know who you are to some extent. Right. Because I got to keep them separate. And so there are the hippocampus. What it'll do is it'll form a memory that's not an Andy Huberman memory. It's an Andy in this place, at this time, in this context. And that's what allows it to support what's called episodic memory, which is your ability to say, I went to Washington D.C. once and I remember going to the Smithsonian. As opposed to your knowledge about what generally happens in Washington D.C. or the President's there. Oh, that's where a lot of politics happen. Oh, the Smithsonian is a place in D.C. it's a memory of your being there at a particular place in time. Now, there's other parts of the brain that allow you to associate that information in a meaningful way and to be able to, to actually expand on that context and create these narratives and these stories about it. Where the prefrontal cortex comes in and it's a huge area, it's about one third of the primate brain. So it's just massive. There are a lot of people who go, well, there's no real. There's a bunch of different areas and all do different things. And I subscribe to the view that that is very true. And at the same time, there's a global function of the prefrontal cortex, which is what's called cognitive control. It's this ability to say, I'm going to regulate my movements and I'm going to regulate my perceptions and my thoughts based on what's important to me in terms of this higher order goal. Right. So when I've tested, for instance, patients with prefrontal lesions, I'm sure Mark Desposito talked to you about this. It's like the hallmark of them. They used to say, well, the prefrontal cortex, it's important, important for working memory. And you could record from neurons in the prefrontal cortex or look at FMRI signal. And if a person or a animal is holding something in their mind, like a phone number, neurons or BOLD signal and MRI will be highly elevated. Their activity will be elevated throughout this period of time where they're holding in mind. But it turns out if you just ask somebody with a major prefrontal lesion, here's a bunch of numbers, 5, 2, 7, 8, you know, ask you to tell them back to me in right order, they can do it just fine. But now I start to distract them. I move my hands around, there's a plane going on, you know, flying outside the window. And I had that literally happen once. Now they start to bomb it because their attention is not controlled by their goal. It's controlled by the environment around them. And so this is where things get really interesting. So I once tested a patient and I'd heard about this, but until you see it, it like doesn't register. It really blew my mind. So there's a test called the Wisconsin Card Sorting Test. And we don't have to get into all the details of it, but basically it's this test where people learn some Rule about where to put a card on a table. Right. And they don't get told the rule, they just learn it. And patients learn this. Prefrontal damage learn it just fine.

Is it that they get a error signal or a correct signal if they're doing it in the right direction over time, they just kind of. The brain figures it out.

Yeah, yeah. So maybe I'll give a little bit more background, but I don't want to go in the.

No, that's okay. I mean, my. If I'm correct, if I'm wrong, I forget the Wisconsin card. So task details. But you know, like they, they're told to just start throwing the cards and that the, the, the, the correct algorithm will reveal itself by a series of error and correct signals. And so maybe I'm taking all the red cards and putting in one pile, black cards and putting them another, Getting error signals so that maybe I go odds, evens. Yeah, maybe I divide by suit. If it's depending on what kind of cards they are, maybe I organized by even odd alteration and sooner or later the brain figures it out.

Yeah, exactly, exactly. And you don't need a prefrontal cortex to do that, which is surprising, but you don't. You can do it.

So there's context dependent action and learning without the prefrontal cortex.

Yes, but let's, let's unpack this context. Right. So now you've been, let's say, putting all the diamonds in one pile. You've been putting all the spades in another pile. Right. So now I change the rule, but I don't tell you. And you put the diamonds, the queen of diamonds in the diamond pile, let's say. And now I say, nope, that's wrong. So now you have to say, wait a minute, that was right all this time. What's going on?

This is like life.

This is like life. Right. The thing that used to be used to work for you no longer works. So you keep doing this and a person with an intact brain will eventually figure out, okay, that's not working. I'll try another strategy. And then they'll learn the new rule. Right. It's not easy, it's a pain, but people will do it. This patient in particular kept on using the old rule. And so you have to give a series of hints going like, what's your strategy here? And they're like, they'll tell you, I'm putting it according to the color. And then you. Okay, well does that appear to be working for you? And they'll go, no, they'll just keep doing it.

They perseverate, they perseverate.

But the interesting thing is he knows it's not working, but he's can't help himself from doing it. And so what the prefrontal cortex is, it's not about this declarative knowledge about what you should do. And I think this is very deep because I think often we get moralistic about people's actions, especially for people who have head injuries or something like that. And it's like you can have all of these beliefs that you want to have, but you need the prefrontal cortex to translate these high order beliefs, things that are very abstract, into actual concrete action. Otherwise what you do is not going to be dictated by that knowledge. So how this relates to memory is we're constantly barraged by information. I think it's. It might have said something like 35 terabytes, I don't know. But it's a big number and the estimates get bigger and bigger every year. So we're barraged by information. There's no way you can even pay attention to it. All right?