Andrew Huberman: Neuroscience of Optimal Performance | Lex Fridman Podcast #139

Lex Fridman 0:00 The following is a conversation with Andrew Huberman, a neuroscientist at Stanford working to understand how the brain works, how it can change through experience, and how to repair brain circuits damaged by injury or disease. He has a great Instagram account @hubermanlab where he teaches the world about the brain and the human mind. Also, he's a friend and an inspiration in that he shows that you can be humble, giving, and still succeed in the science world. Quick mention of each sponsor followed by some thoughts related to the episode. Eight Sleep, a mattress that cools itself and gives me yet another reason to enjoy sleep. SEMrush, the most advanced SEO optimization tool I've ever come across. And Cash App, the app I use to send money to friends. Please check out these sponsors in the description to get a discount and to support this podcast. As a side note, let me say that I heard from a lot of people about the previous conversation I had with Yaron Brook about objectivism. Some people loved it, some people hated it. I misspoke in some parts, was more critical on occasion than I'm meant to be, didn't push on certain points that I should have, was under-educated or completely unaware about some major things that happened in the past or major ideas out there. I bring all that up to say that if we are to have difficult conversations, we have to give each other space to make mistakes, to learn, to grow. Taking one or two statements from our three-hour podcast and suggesting that they encapsulate who I am, I was, or ever will be is a standard that we can't hold each other to. I don't think anyone could live up to that kind of standard, at least I know I can't. The conversation with Yaron is mild relative to some conversations that I will likely have in the coming year. Please continue to challenge me, but please try to do so with love and with patience. I promise to work my ass off to improve. Whether I'm successful at that or not, we shall see. If you enjoy this thing, subscribe on YouTube, review it with five stars on Apple Podcasts, follow on Spotify, support on Patreon, or connect with me on Twitter @lexfridman. And now here's my conversation with Andrew Huberman.

Lex Fridman 2:30 You've mentioned that in your lab at Stanford, you (laughs) induce stress by putting people into, uh, virtual reality and having them go through one of a set of experiences, I think you mentioned this on Rogan or with Whitney, that scare them.

Andrew Huberman 2:44 Mm-hmm.

Lex Fridman 2:44 So just, uh, on a practical, psychological level and maybe on a philosophical level, wha- what are people afraid of? What are the fears? What are these fear experiences (laughs) that you find to be effective?

Andrew Huberman 2:59 Yeah, so it depends on the person obviously, um, and we should probably define fear, right? 'Cause you can...

Lex Fridman 3:05 (laughs) Yeah.

Andrew Huberman 3:05 Uh, w- without going too far down the rabbit hole of...

Lex Fridman 3:07 Yeah.

Andrew Huberman 3:07 ... of defining these things. Um, you know, you can't really have fear without stress, but you could have stress without fear. And you can't really have trauma without fear and stress, but you could have fear and stress without trauma. So, you know, we can start playing the word game, and that actually is one of the motivations for even having a laboratory that studies these things is that we really need better physiological, neuroscientific, and operational definitions of what these things are.

Lex Fridman 3:33 Okay.

Andrew Huberman 3:33 I mean, the, the field of understanding, um, emotions and states, which is mainly what I'm interested in, is very complicated, but we can, um, we can do away with a lot of complicated debate and say in our laboratory what we're looking for to assign it a value of fear is a big inflection in autonomic arousal, so increases in heart rate, increases in breathing, u- um, perspiration, pupil dilation, all the hallmark signature features of the stress response.

Lex Fridman 4:05 Mm-hmm.

Andrew Huberman 4:06 Uh, and in some cases, we have the benefit of getting neurosurgery patients where we've got electrodes in their amygdala, in their insula, in their orbital frontal cortex, um, down beneath the skull, so these are chronically implanted electrodes, we're getting multiunit signals and we can start seeing some central features of, uh, meaning within the brain. And what's interesting is that as trivial as it might seem in listening to it, almost everybody responds to heights and falling from a high virtual place with a very strong stress, if not fear response. And that's because the visual vestibular apparatus eye, right, the, the optic flow and how it links to the, you know, balanced semicircular canals of the inner ears, all this technical stuff, but really all of that pools all your physiology. The, the feeling that your stomach is dropping, the feeling that you're... Suddenly you're sweating even though you're not afraid of falling off this virtual platform, but you feel as if you're following- falling, excuse me, because of the optic flow. That one is universal. So we've got a dive with great white sharks experience where you actually exit the cage, we went out and-

Lex Fridman 5:18 (laughs)

Andrew Huberman 5:18 ... did this in the real world and brought back 360 video that's built out pretty...

Lex Fridman 5:23 Oh, so this is actual 360 video? That's awesome.

Andrew Huberman 5:24 360 video, and this was important to us, right? So when we decided to set up this platform, a lot of the motivation was that a lot of the studies of, of these things in laboratories, I don't want to call them lame because I want to be respectful of the, the people that did this stuff before, but they study fear by, you know, showing subjects a picture of a bloody arm...

Lex Fridman 5:43 Right.

Andrew Huberman 5:43 ... or a snake, or something like that, or... And it just, unless you have a snake phobia, it just wasn't creating a real enough experience. So we need to do something where people aren't gonna get injured, but where we can tap into the physiology and that thing of presence of people momentarily, not the whole time, but momentarily-...forgetting they're in a laboratory.

Lex Fridman 6:02 Mm-hmm.

Andrew Huberman 6:02 And so heights will always do it. And I, if people want to challenge me on this, I like to point to that movie Free Solo, which was wild because, you know, it's an incredible movie, but I think a lot of its popularity can be explained by a puzzle, which is, you knew he was gonna live when you walked in the theater...

Lex Fridman 6:21 Yeah.

Andrew Huberman 6:21 ...or you watched it on, at home. You knew before that he, he survived, and yet it was still scary, that people were somehow able to put themselves into that experience or into Alex's experience enough that they, they were concerned or worried or afraid at some level. So heights always does it. If we get people who have generalized anxiety, these are people who wa- wake up and move through life at a generally higher state of autonomic arousal and anxiety, then we can tip them a little bit more easily with things that don't necessarily get everyone afraid, things like, um, claustrophobia, public speaking. That's gonna vary from person to person. Um, and then if you're afraid of sharks, like my sister, for instance, is afraid of sharks, she won't even come to my laboratory, because there sh- there's a thing about sharks in it. That's how terrified some people are of these specific stimuli. But heights gets them every time.

Lex Fridman 7:15 Yeah.

Andrew Huberman 7:15 And...

Lex Fridman 7:16 I'm terrified of heights.

Andrew Huberman 7:17 It, it's... You know, when we have you step off a platform, virtual platform, and it's a flat floor in my lab, but we... You're up there.

Lex Fridman 7:26 Well, you actually allow them the possibility in the virtual world to actually take the leap of faith?

Andrew Huberman 7:32 Yeah, maybe I should describe a little bit of the experiment. So, um, without giving away too much, in case someone wants to be a subject in one of these, uh, experiments, we have them playing a cognitive game. It's a simple lights out kind of game where you're, you know, pointing a cursor and turning out lights on a grid. But it gets increasingly complex and it speeds up on them, and, um, you know, there's a failure point for everybody where they just can't make the motor commands fast enough. And then we surprise people, essentially, by placing them virtually. All of a sudden, they're sus- they're on a narrow platform between two buildings.

Lex Fridman 8:04 Yeah.

Andrew Huberman 8:04 And then we encourage them or we cue them with a, with a... By talking to them through a microphone to continue across that platform to continue the game. And, you know, some people, they, they just won't d- they actually will hold... Get down on the ground and hold onto a virtual beam that doesn't even exist on a flat floor. And so what this really tells us is the power of the brain to enter these virtual states as if they were real. And we really think that anchoring the visual and the vestibular, the balance components of the nervous system, are what bring people into that presence so quickly. There's also the potential, and we haven't done this yet, to bring in 360 sound. So the reason we did 360 video is that when we started all this back in 2016, a lot of VR was pretty lame, frankly. It was CGI. It just wasn't real enough. But with 360 video, we knew that we could get people into this presence where they think they're in a real experience more quickly. And our friend, Michael Moller, who I was introduced to because of the project, I reached out to some friends. Michael Moller's a very famous, um, portrait photographer in Hollywood, but he dives with great white sharks and he leaves the cage.

Lex Fridman 9:13 Mm-hmm.

Andrew Huberman 9:13 And so we worked with him to build a 360 video apparatus that we could swim under water with, went out to Guadalupe Island, Mexico, and actually-

Lex Fridman 9:23 Awesome.

Andrew Huberman 9:23 ...got the experience. It was a lot of fun. It was a, there was some interesting moments out there of danger, but it w- came back with that video and built that for the sharks, and then we realized we need to do this for everything. We need to do it for heights, we need to do it for public speaking, for claustrophobia. And what's, what's missing still is 360 sound, where 360 sound would be, uh, for instance, um, if I were to turn around and there was a, like a giant attack dog there, the moment I would turn around and see it, the dog would growl. But if I turned back toward you...

Lex Fridman 9:52 Right.

Andrew Huberman 9:52 ...then it would, it would be silent. So, and that brings a very real element to one's own be- behavior, where you don't know what's gonna happen if you turn a corner. Whereas if there's a dog growling behind me, and I'm, and I turn around and then I turn back to you and it's still growling...

Lex Fridman 10:07 Yeah.

Andrew Huberman 10:07 ...that might seem like more of an impending threat, but, um... And sustained threat, but actually, it's when you start linking your own body movements to the experience. So when it's closed loop...

Lex Fridman 10:18 Mm.

Andrew Huberman 10:18 ...where my movements and choices are starting to influence things, and I, they're getting scarier and scarier, that's when you can really drive people's nervous systems down these paths of high, high states of stress and fear. Now, we don't wanna traumatize people, obviously...

Lex Fridman 10:32 Right.

Andrew Huberman 10:32 ...but, uh, we also, we also study a number of tools to, that allow them to calm themselves in these environments.

Lex Fridman 10:37 S-

Andrew Huberman 10:37 So the short answer is heights.

Lex Fridman 10:39 Heights (laughs) .

Andrew Huberman 10:39 Yeah (laughs)

Andrew Huberman 10:41 .

Lex Fridman 10:41 Well, from a psychology and from a neuroscience perspective, this whole construction that you've developed is fascinating. We did this a little bit with autonomous vehicles, so to try to understand the decision-making process of a pedestrian when they cross the road, and trying to create an experience of a car, you know, that could run you over, so there's the danger of there. I was so surprised how real that whole world was, and the graphics that we built wasn't ultra-realistic or anything, but I was still afraid of being hit by a car. E- everybody we tested were really afraid of being hit by that car.

Andrew Huberman 11:22 Even though it was all a simulation?

Lex Fridman 11:23 It was all a simulation. It was, uh, it was kind of boxy, actually.

Andrew Huberman 11:27 Mm-hmm.

Lex Fridman 11:27 I mean, it wasn't like ultra-realistic simulation. And it's fascinating.

Andrew Huberman 11:31 I mean, l- looms and heights. So, any kind of depth, we're just programmed to, um, to not necessarily recoil, but to be cautious about that edge and that depth. And then looms, things coming at us that are getting larger. There are looming sensing neurons even in the retina...

Lex Fridman 11:48 Mm-hmm.

Andrew Huberman 11:48 ...at the very, very early stage of visual processing. And, um, incidentally, uh, the way...... Mueller and, you know, folks learned how to not get eaten by great white sharks when you're swimming outside the cage is as they start c- lumbering in, you swim toward them. And they get very confused when you loom on them.

Lex Fridman 12:07 Okay.

Andrew Huberman 12:07 Because clearly you're smaller, clearly they could eat you if they wanted to, but there's something about forward movement toward, uh, any creature that that creature questions whether or not it would be a good idea to generate forward movement toward you. And so that's actually the survival tool of these cage exit white shark divers.

Lex Fridman 12:26 Are you playing around with... Like, one of the critical things for the autonomous vehicle research is you couldn't do 360 video because the, there's a game theoretic, there's an interactive element that's really necessary. So maybe people realize this, maybe they don't, but 360 video, you obviously... Well, it's actually not that obvious to people, but you can't change the reality that you're watching. (laughs)

Andrew Huberman 12:49 That's right.

Lex Fridman 12:50 So, uh, but you find that that's... Like, is there something fundamental about fear and stress that the interactive element is essential for? Or do you find you can, you can arouse people with just the video?

Andrew Huberman 13:05 Great question. Um, it works best to use mixed reality. So we have a snake stimulus. Uh, I personally don't like snakes at all. I don't mind spiders, we also have a spider stimulus, but, like, snakes, I just don't like them.

Lex Fridman 13:17 Yeah.

Andrew Huberman 13:17 There's something about the, the slithering and the... It just, it creates a visceral response for me. Um, some people not so much and they have lower levels of stress and fear in there. But one way that we can get them to feel more of that is to use mixed reality where we have a, an actual physical bat and they have to stomp out the snake as opposed to just m- um, walk to a little safe corner.

Lex Fridman 13:42 Mm-hmm.

Andrew Huberman 13:42 Which then makes the snake disappear. That tends to be not as stressful as if they have a physical weapon. And so you got people in there, you know, banging on the floor...

Lex Fridman 13:50 (laughs)

Andrew Huberman 13:50 ... against this thing, and there's something about engaging that makes it more of a th- more of a threat. Now I should also mention...

Lex Fridman 13:57 That's true.

Andrew Huberman 13:57 ... we, we always get the subjective report from the subject of what they experienced because I, we never wanna project our own ideas about what they were feeling, but that's the beauty of working with humans is you can ask them how they feel.

Lex Fridman 14:09 Exactly.

Andrew Huberman 14:10 And humans aren't great at explaining how they feel, um, but it's a lot easier to understand what they're saying than a mouse or a macaque monkey is saying. (laughs) Um, so it's the best we can do is language plus these physiological and neurophysiological

Andrew Huberman 14:25 signals.

Lex Fridman 14:25 Is there something you've learned about yourself, about your deepest fears? Like, you said snakes. Is there something that... Like, if I were to torture you, I'm, so I'm Russian, so, you know, I always kinda think how can I murder this people then, this person that entered the room, but also how, how can I torture you to get some information out of you? What, w- what, what would I go with?

Andrew Huberman 14:47 Hmm. It's interesting you should say that. I never considered myself claustrophobic.

Lex Fridman 14:51 Mm-hmm.

Andrew Huberman 14:51 But, um, 'cause I don't mind small environments pr- provided they're well-ventilated, but I, uh, before COVID, I started going to this Russian banya.

Lex Fridman 15:02 Yeah.

Andrew Huberman 15:02 Um, you know...

Lex Fridman 15:03 (laughs)

Andrew Huberman 15:03 ... in the ******* area, and I had never been to a banya.

Lex Fridman 15:05 Yeah.

Andrew Huberman 15:05 So, you know, the whole experience of really, really hot sauna.

Lex Fridman 15:08 Yeah.

Andrew Huberman 15:08 And, uh, what do they call it? The plotza? They're hitting you with the leaves and...

Lex Fridman 15:12 Yeah.

Andrew Huberman 15:12 And it gets really hot and humid in there, and there were a couple times where I thought, "Okay, this thing is below ground, it's in a city where there are a lot of earthquakes, like, if this place crumbled and we were stuck in here." And I'd start getting a little panicky.

Lex Fridman 15:28 Yeah.

Andrew Huberman 15:28 And I realize and I'm like, "I don't like small, confined spaces with poor ventilation." So I realize, I think I have some claustrophobia, and I wasn't aware of that before. So I've put myself into our own claustrophobia stimulus which involves getting into an elevator...

Lex Fridman 15:43 Mm-hmm.

Andrew Huberman 15:44 ... um, and, with a bunch of people, virtual people, and the elevator gets stalled. And at first you're fine, you feel fine, but then as we start modulating the environment and we actually can control levels of oxygen in the environment if we want to, um, it is really uncomfortable for me and I never would have thought... You know, I fly, I'm comfortable in planes, I... But it is really uncomfortable and so I think I've un-

Lex Fridman 16:09 Claustrophobia.

Andrew Huberman 16:09 ... unhatched a bit of, uh, claustrophobia.

Lex Fridman 16:11 Yeah.

Andrew Huberman 16:11 Yeah.

Lex Fridman 16:13 Yeah, for me as well probably. That one, that one's pretty bad. The heights I try to overcome, so I went skydiving to try to overcome the fear of heights, but that didn't help.

Andrew Huberman 16:23 Did you jump out?

Lex Fridman 16:23 Yeah, I ju-

Andrew Huberman 16:24 All right.

Lex Fridman 16:24 Yeah, I ju- jumped out, but it was, it was a, it was fundamentally different experience than... I guess there could be a lot of different flavors of fear of heights maybe.

Andrew Huberman 16:33 Mm-hmm.

Lex Fridman 16:34 But the one I have didn't seem to be connected to s- jumping out of a plane because they're very different, 'cause, like, once you accept that you're going to jump then it's, it's a different thing. I, I think what I'm afraid of is the moments before it is, is the mo- is the scariest part.

Andrew Huberman 16:54 Absolutely.

Lex Fridman 16:55 And, and I, I don't think that's emphasized in the skydiving experience as much, and also just the acceptance of the fact that it's going to happen. So, so once you accept that it's going to happen, it's not as scary. It's the fact that it's not supposed to happen and it might, that's the scary part. That... I, I guess I'm not being eloquent in this des- description, but there's something about skydiving that, uh, was actually philosophically liberating. I was, it was... I was like, "Wow, it, it was, uh..." The possibility that you can walk on a surface and then at a certain point there's no surface anymore to walk on and it's all of a sudden the world becomes three-dimensional and there's this freedom of floating, that the concept of, like, of Earth disappears for a brief few seconds. I don't know. That was, that was...

Andrew Huberman 17:45 Wild.

Lex Fridman 17:45 That was wild but I'm still terrified of heights,

Lex Fridman 17:48 so... I mean, one, one thing I, I wanna ask just on fear 'cause it's so fascinating is have you, um, learned anything about what it takes to overcome fears?

Andrew Huberman 18:00 Yes. And that comes from two, from a, you know, research study standpoint, uh, two parallel tracks of research. One was done actually in mice, uh, 'cause we have a mouse lab also, c- where we can probe around different brain areas and try and figure out what interesting brain areas we might wanna probe around in humans. And a graduate student in my lab, she's now at Caltech, um, Lindsay Salé, um, published a paper back in 2018 showing that w- what at first might seem a little bit obvious, but the mechanisms are not, which is that there are really three responses to fear. You can pause, you can freeze essentially, um, you can retreat, you can back up, or you can go forward. And there's a single hub of neurons in the mid-brain, in the m- it's actually not the mid-brain, but it's, it's in the middle of the thalamus, which is a forebrain structure. Uh, and depending on which neurons are active there, there's a much higher probability that a mouse, or it turns out or a human will advance in the face of fear, or will pause or will, will retreat. Now that just assigns a neural structure to a behavioral phenomenon. But what's interesting is that it turns out that the lowest level of stress or autonomic arousal is actually associated with the pausing and freezing response.

Lex Fridman 19:16 Mm-hmm.

Andrew Huberman 19:18 Then as the threat becomes more impending, and we used visual looms in this case, the retreat response has a slightly higher level of autonomic arousal and stress. So think about playing hide and go seeking, you're trying to stay quiet in a, uh, in a closet that you're hiding. If you're very calm, it's easy to stay quiet and still. As your level of stress goes up, it's harder to maintain that level of quiet and stillness. You see this also in animals that are stalking. A cat will chatter its teeth. That's actually sort of top-down inhibition and trying to restrain behavior. So the freeze response is actually an active response, but it's fairly low stress. And what was interesting to us is that the highest level of autonomic arousal was associated with the forward movement toward the threat, so in your case, um, jumping out of the plane. However, the forward movement in the face of threat was linked to the activation of what we call collateral, which means just a side connection, literally a wire in the brain that connects to the dopamine circuits for reward. And so when one safely and adaptively, meaning you survive, moves through a threat or toward a threat, it's rewarded as a positive experience.

Lex Fridman 20:32 Mm-hmm.

Andrew Huberman 20:32 And so the key, it actually maps very well to cognitive behavioral therapy and a lot of the existing treatments for trauma, is that you have to confront the thing that makes you afraid. So otherwise you exist in this very low level of reverberatory circuit activity where the, the circuits for autonomic arousal are humming and they're humming more and more and more. And we have to remember that, that stress and fear and threat were designed to agitate us so that we actually move. Th- so the reason I mention this is that I think a lot of times people think that the maximum, you know, stress response or fear response is to freeze and to lock up.

Lex Fridman 21:09 Yeah.

Andrew Huberman 21:10 But that's actually not the maximum stress response. The maximum stress response is to advance, but it's associated with reward. It has positive valence.

Lex Fridman 21:18 Oh, interesting word.

Andrew Huberman 21:19 So it, so there's this kind of, everyone always thinks about the bell sh- you know, the sort of hump shape, uh, curve for, you know, at low levels of arousal performance is low and as it increases, performance goes higher and then it drops off as you get really stressed. But there's another bump further out the distribution-

Lex Fridman 21:35 Mm-hmm.

Andrew Huberman 21:35 ... where you perform very well under very high levels of stress. And so we've been spending a lot of time in humans and in animals exploring what it takes to get people comfortable to go to that place, and also to let them experience how there are heightened states of cognition there. There's, um, changes in time perception that allow you to evaluate your environment in fast, at a faster frame rate essentially. This is the matrix-

Lex Fridman 22:00 Mm-hmm.

Andrew Huberman 22:00 ... as a lot of people think of it.

Lex Fridman 22:02 Yeah.

Andrew Huberman 22:02 Um, but we tend to think about fear as all the low level stuff where things aren't worked out, but there are many, um, there are a lot of different features to the fear response, and so we think about it quantitatively and we think about it from a circuit perspective in terms of outcomes and we try and weigh that against the threat. So we never want people to put themselves in unnecessary risk, but that's where the VR is fun because you can push people hard without risk of physically injuring them.

Lex Fridman 22:30 And that's, uh, like you said, it's a little bump. That, that seems to be a very small fraction of the human experience, right? So it's kind of fascinating to study it 'cause, um, most of us move through life without ever experiencing that kind of, uh, focus.

Andrew Huberman 22:48 Well, everything's in a peak state there. I really think that's where optimal performance lies.

Lex Fridman 22:53 There's so many interesting words here, but what's performance and what's optimal performance? We're talking about mental ability to, what, to perceive the environment quickly, to make actions quickly? What's optimal performance?

Andrew Huberman 23:09 Yeah. Well, it's very subjective and it varies depending on, um, task and environment. So o- one way where we can make it a little bit more operational-

Lex Fridman 23:18 Mm-hmm.

Andrew Huberman 23:18 ... and concrete is to say, um, there is a sweet spot, if you will, where the level of internal autonomic arousal, AKA stress or alertness, whatever you want to call it, is ideally matched to the speed of whatever challenge you happen-

Lex Fridman 23:36 Got it. Yeah.

Andrew Huberman 23:37 ... to be facing in the outside world. So we all have, um, perception of the outside world as exteroception and the perception of our internal real estate, interoception. And when those two thi- when interoception and exteroception are matched along a couple dimensions, performance, uh, tends to increase, eh, or tends to be in, in an optimal range. So for instance, if you're ... I don't play guitar, but I know you play guitar. So let's say you're trying to learn something new on the guitar.I'm not saying that being in these super high states of activation are the best place for you to be in order to learn. It may be that you, your internal arousal needs to be at a level where your analysis of space and time has to be well-matched to the information coming in, and what you're trying to do in terms of performance, in terms of playing chords...

Lex Fridman 24:26 Yeah.

Andrew Huberman 24:26 ... and notes and so forth. Now, in these cases of high threat where things are coming in quickly and animals and humans need to react very quickly, the higher your state of autonomic arousal, the better, because you're slicing time more finely just because of the way the autonomic system works. It, you know, the- the pu- pu- uh, pupil dilation for instance and movement of the lens essentially changes your- your optics. Now that's obvious. But in, with the change in optics is a change in how you bend time and slice time, which allows you to s- get more frames per second read out. With the guitar learning for instance, it might actually be that you wanna be almost sleepy.

Lex Fridman 25:05 Mm-hmm.

Andrew Huberman 25:05 Almost in a, uh, kind of drowsy state to be able to, uh, and I don't play music, so I can't...

Lex Fridman 25:11 Mm-hmm.

Andrew Huberman 25:11 I'm guessing here, but sense some of the nuance in the chords or the ways that you're, uh, to be relaxed enough that your fingers can follow an external queue. So matching the movement of your fingers to something that's pure exteroception.

Lex Fridman 25:22 Mm-hmm.

Andrew Huberman 25:23 And so there is no perfect autonomic state for, uh, performance. This is why I don't favor terms like flow...

Lex Fridman 25:33 Mm-hmm.

Andrew Huberman 25:33 ... because they're not well operationally de- defined enough. But I do believe that optimal or peak performance is going to arise when internal state is ideally matched to the s- base time features of the external demands.

Lex Fridman 25:49 So there's so- some slicing of time that happens and then you're, you're able to adjust, s- slice time more finely or more, less finely in order to adjust to the, the stimulus, the dynamics of

Lex Fridman 26:02 the stimulus. What about the, the realm of ideas? So like, you know, I'm, I'm a big believer... Uh, this guy named Cal Newport who wrote a book about Deep Work.

Andrew Huberman 26:13 Oh, yeah. I love that book.

Lex Fridman 26:13 (laughs) Yeah, he's great. Uh, so, uh, he, uh, I mean, one of the nice things I've always practiced Deep Work but he, it's- it's always nice to have words, uh, put to the, the concepts that you've practiced. It somehow makes them more concrete, and allows you to, uh, to get better. It- it turns into a skill that you can get better at. But, you know, I also value deep thinking where you think... It's almost meditative. You think about a particular concept for long periods of time. The programming you have to do that kinda thing for. You just have to hold this concept like, like you- you hold it, and then you take steps with it, you take further steps, and you're- you're holding relatively complicated things in your mind as you're thinking about them. And there's a lot of... I mean, the hardest part is there's, uh, frustrating things like, you take a step and it turns out to be the wrong direction, so you have to calmly turn around and take a step back. And then, as you're kinda like exploring through the space of ideas, is there something about your study of optimal performance that could be applied to the act of thinking...

Andrew Huberman 27:25 Mm-hmm.

Lex Fridman 27:26 ... as opposed to action?

Andrew Huberman 27:28 Well, we haven't done, uh, too much work there but what, um, but I think I can comment on it...

Lex Fridman 27:32 Yeah.

Andrew Huberman 27:33 ... from a neuroscience perspective.

Lex Fridman 27:34 Yeah, what's your intuition about it?

Andrew Huberman 27:34 Which is really all I do is that I...

Lex Fridman 27:36 Yeah.

Andrew Huberman 27:36 Well, I mean, we do experiments in the lab but, um, looking at things through the lens of neuroscience. So what you're describing, um, can be mapped fairly well to working memory, just keeping things online and updating them as they change and information is coming back into- into your brain. Uh, Jack Feldman, who I'm a huge fan of and, um, fortunate to be friends with, is a, uh, professor at UCLA, works on respiration and breathing, but he has a physics background and, um, and so he thinks about respiration and breathing in terms of ground states and how they modulate other states, a very- very interesting and I think, um, important work. Jack, uh, has an answer to your question.

Lex Fridman 28:18 Mm-hmm.

Andrew Huberman 28:18 So I'm not gonna get this exactly right 'cause this is lifted from a coffee conversation that we had...

Lex Fridman 28:22 (laughs)

Andrew Huberman 28:22 ... about a month ago but, uh, so, um, apologies in advance for the... But I think I can get it mostly right. So we were talking about this, about how the brain updates cognitive states depending on demands, and thinking in particular. And he used an interesting example, I'd be curious to know if you- you agree or disagree. Uh, he said, you know most great mathematics is done by people in their late teens and 20s.

Lex Fridman 28:48 Mm-hmm.

Andrew Huberman 28:49 And even you could say early 20s. Sometimes into the late 20s but not much further on.

Lex Fridman 28:54 Yeah.

Andrew Huberman 28:54 Maybe I just insulted some mathematicians but...

Lex Fridman 28:56 No, that's- that's- that's true.

Andrew Huberman 28:58 And I think that it demands... His argument was, um, there's a tremendous demand on working memory to work out theorems in math, and to keep a number of plates spinning, so to speak, mentally, and run back and forth between them updating them. In physics, Jack said, and I- I'm in cl- I think this makes sense to me too, that there's a reliance on working memory but an increased reliance on some s- sort of deep, deep memory and deep memory stores, probably stuff that's moved out of the hippocampus and forebrain and into the cortex, and is, um, more, y- some episodic and declarative stuff but really so you're- you're pulling from your library basically...

Lex Fridman 29:39 Mm-hmm.

Andrew Huberman 29:39 It's not all RAM, it's not all working memory. And then in biology, the, and physicists tend to have very active careers into their, you know, 30s and 40s and 50s and so forth, um, sometimes later. And then in biology, you see careers that are, have a much longer arc. You get kind of these protracted (laughs) careers often, uh, people still in their 60s and 70s doing- doing really terrific work.... not always doing it with their own hands, 'cause there are people in the labs who are doing them, of course. But, um, and that work does tend to rely on insights gained from having a very deep knowledge base, where you can remember a paper and a, or maybe a figure in a paper, you could go look it up if you wanted to. But it's very different than the working memory of the mathematician. And so, when you're talking about coding or being in that tunnel of thought and trying to iterate and keeping a lot of plates spinning, it, it speaks directly to working memory. My lab hasn't done too much of that.

Lex Fridman 30:37 With working memory?

Andrew Huberman 30:37 But we are pushing working memory when we have people do things like the simple lights out tasks while they're under ... We can increase the cognitive load by increasing the level of autonomic arousal to the point where they start doing less well.

Lex Fridman 30:51 Yeah.

Andrew Huberman 30:52 And, you know, everyone has a cliff. This is what's kind of fun. We've had, um, you know, SEAL team operators come to the lab. We've had people from other units in the, uh, military very ... You know, we've had range of, of intellects and backgrounds and all sorts of things, and everyone has a cliff. And those cliffs, uh, sometimes show up as a function of s- the demands of speed of processing or how many things you need to keep online. I mean, we're all limited at some point in the number of things we can keep online. So what you're describing is very interesting because it, I think it has to do with how narrow or broad the information set is. Beca- And I don't program, I'm not a active programmer, so, um, this is a regime I don't really fully know, so I don't wanna comment about it, uh, in th- in any way, uh, that, you know, doesn't suggest that. But I think that what you're talking about is top-down control, so this is prefrontal cortex keeping every bit of reflexive circuitry at bay, the one that makes you wanna get up and use the restroom, the one that makes you wanna check your phone, the ... All of that, but also running these anterior thalamus to prefrontal cortex loops which we know are very important for working memory.

Lex Fridman 32:02 Yeah. Let, let me try to think through this a little bit. Uh, so, reducing the process of thinking to working memory access is tricky. It's probably ultimately correct, but if I were to say some of the most challenging things that, uh, an engineer has to do, and a sci- a scientific thinker, I would say it's kinda depressing to think that we do that best in our 20s, but is, uh, this kind of first principles thinking step of, of saying you, you're accessing the things that you know and then saying, "Well, let me ... How do I do this differently than I've done it before?" This, this weird, like, stepping back, like, "Is this right? Let's try it this other way." That, that's the most mentally taxing step is like y- you've gotten quite good at this particular pattern of how you solve this particular problem, so there's a, there's a pattern recognition first. You're like, "Okay, I know how to, how to build a thing that solves this particular problem," in programming, say. And then the question is, but can I do it much better? And I don't know if that's ... I don't know what the hell that is. I don't know if that's accessing working memory. That's, that's almost access ... Maybe it is accessing memory in the sense that it's trying to find similar patterns in a totally different place that it can be, uh, projected onto this. But you're, you're, it's ... You're not querying, uh, facts. You're querying, like, functional things, like ...

Andrew Huberman 33:48 Yeah, it's patterns. I mean, you're running al-

Lex Fridman 33:50 Patterns.

Andrew Huberman 33:50 You're, you're testing algorithms.

Lex Fridman 33:52 Yeah.

Andrew Huberman 33:52 Right? You're testing algorithms. I-

Lex Fridman 33:53 Yes.

Andrew Huberman 33:54 So I wanna just, um, because I know, uh, some of the people listening to this, and you ha- will have basis in, you know, scientific training and episcientific training, so I wanna be clear. I think we can be correct about some things, like the role of working memory in these kinds of processes, without being exhaustive. We're not saying they're the only thing.

Lex Fridman 34:13 Right, right.

Andrew Huberman 34:13 We're not ... You know, we can be correct but not assume that that's the only thing involved, right?

Lex Fridman 34:18 Right.

Andrew Huberman 34:18 And, I mean, neuroscience, let's face it, is still in its infancy. I mean, we probably know 1% of what there is to know about the brain. Um, you know, we've learned so much and yet th- there may be global states that underlie this that make prefrontal circuitry work differently than it would in a, in a different regime, or even time of day. I mean, there's a lot of mysteries about this. But ... So I just wanna make sure that we, we sort of are a- we're aiming for precision and accuracy, but, but we're not gonna be-

Lex Fridman 34:46 (laughs) We lost that.

Andrew Huberman 34:46 We're not gonna be exhaustive.

Lex Fridman 34:48 Yeah.

Andrew Huberman 34:48 So there's a difference there, and I think, uh, you know, sometimes in the vastness of the internet, uh, that gets forgotten. Um, so the other is that, um, you know, we, we think about, um, you know, we think about these operations, uh, at, you know, really focused, keeping a lot of things online, but what you were describing is actually, um, it, it speaks to the, the very real possibility, probably the, the ... With certainty, there's another element to all this, which is when you're trying out lots of things, in particular lots of different algorithms, you don't want to be in a h- in a state of very high autonomic arousal. That's not what you want, because the higher level of autonomic arousal and stress in the system, the more rigidly you're gonna analyze space and time.

Lex Fridman 35:36 Right.

Andrew Huberman 35:37 And what you're talking about is playing with spacetime dimensionality, and I wanna be very clear, I'm, you know, I'm the son of a physicist, I am not a physicist, and when I talk about space and time, I'm literally talking about visual space and-... how long it takes for my finger to move from this point to this point.

Lex Fridman 35:53 You, you are facing a tiger and trying to figure out how to avoid being eaten by the tiger...

Andrew Huberman 35:58 And that's primarily-

Lex Fridman 35:59 ... in space and time.

Andrew Huberman 35:59 ... gonna be determined by the visual system in humans.

Lex Fridman 36:02 Yeah.

Andrew Huberman 36:02 We don't walk through space, for instance, like a scent hound would and look at three-dimensional scent plumes. You know, when a scent hound goes out in the environment, they have depth to their odor trai- the odor trails they're following.

Lex Fridman 36:15 Wow. That's awesome.

Andrew Huberman 36:15 And they don't think about them, uh, uh, we don't think about odor trails. You might say, "Oh, well, the smell is getting more intense, aha."

Lex Fridman 36:21 Yeah.

Andrew Huberman 36:21 But they actually have three-dimensional odor trails.

Lex Fridman 36:24 Yeah.

Andrew Huberman 36:24 So they see a cone of odor.

Lex Fridman 36:26 Right, fascinating.

Andrew Huberman 36:26 See, of course, with their nose, with their olfactory cortex. We do that with our visual system, and we parse time often subconsciously with, mainly with our visual system, also with our auditory system, and this shows up, for the musicians out there, metronomes are a great way to play with this. Um, you know, bass drumming, when the frequency of bass drumming changes, your, your perception of time changes quite a lot. So in any event, space and time are linked in the, through the sensory apparati, through the eyes and ears and nose, and, um, probably through taste too and through touch, um, for us, but mainly through vision. So when you drop into some coding or iterating through a creative process or trying to solve something hard, you can't really do that well if you're in a rigid, um, high level of autonomic arousal because you're plugging in algorithms that are in this space regime, this time regime matches. It's spacetime match. Whereas creativity, I always think the lava lamp is actually a pretty good example, even though it has these counterculture, new age-y connotations, because you actually don't know which direction things are gonna change. And so in drowsy states, sleeping and drowsy states, space and time become dislodged from one another somewhat, and they're very fluid, and I think that's why a lot of solutions come to people after sleep and naps, and this could even take us into a discussion, if you like, about psychedelics and what... We now know, for instance, that people thought that psychedelics work by just creating spontaneous bursting of neurons and hallucinations.

Lex Fridman 37:59 Mm-hmm.

Andrew Huberman 37:59 But the, the 5-H, 2CA, uh, 2C and 2A receptors, which are the main sites for things like LSD and psilocybin and some of the other, um, halluci- the ones that create hallucinations, the drugs that create hallucinations. The, most of those receptors are actually in the, um, collection of neurons that encase the thalamus, which is where all the sensory information goes into, a structure called the thalamic reticular nucleus, um, and it's an inhibitory structure that make sure that when we're sitting here talking, that I'm mainly focused on whatever I'm seeing visually, that I'm essentially eliminating a lot of sensory information. Under conditions where people take psychedelics and these, uh, particular serotonin receptors are activated, that inhibitory shell, it's literally shaped like a shell, starts losing its ability to inhibit the passage of sensory information.

Lex Fridman 38:53 Mm-hmm.

Andrew Huberman 38:54 But mostly, the effects of psychedelics are because the lateral connectivity in layer five of cortex across cortical areas is increased and what that does is that means that the spacetime relationship for vision, like moving my finger from here to here, very rigid spacetime relationship, right? If I slow it down, it's slower obviously, but there's a prediction that can be made based on the neurons in the retina and the cortex. On psychedelics, this could be very strange experience.

Lex Fridman 39:20 Yeah. (laughs)

Andrew Huberman 39:21 But the auditory system has one that's slightly different spacetime, and they're matched to one another in deeper circuits in the brain.

Lex Fridman 39:28 Mm-hmm.

Andrew Huberman 39:28 The olfactory system has a different spacetime relationship to it. So under conditions of, of these increased activation of these serotonin receptors, space and time across sensory areas starts being fluid. So I'm no longer running the algorithm for moving my finger from here to here and making a prediction based on vision alone, I'm now... This is where people talk about, um, hearing-

Lex Fridman 39:53 Mm-hmm.

Andrew Huberman 39:53 ... sights, right? You start linking the, this might actually make a sound in a psychedelic state. Now, I'm not suggesting people run out and do psychedelics because it's very disorganized, but essentially what you're doing is you're mixing the algorithms. And so when you talk about being able to access new solutions, you don't need to rely on psychedelics. If people choose to do that, that's their business. But in drowsy states, this lateral connectivity is increased as well, the shell of the thalamus shuts down, and what's ha- these are through these so-called pons geniculate occipital waves. And what's happening is you're getting whole brain activation at a level that you start mixing algorithms.

Lex Fridman 40:30 Mm-hmm.

Andrew Huberman 40:30 And so sometimes I think solutions come not from being in that narrow tunnel of spacetime and strong activation of working memory and trying to, well, iterate if this, then this, very strong deductive and inductive thinking and working from first principles, but also from states where something that was a, an algorithm that never, you never had in existence before suddenly gets lumped with another algorithm.

Lex Fridman 40:54 Mm-hmm.

Andrew Huberman 40:55 And all of a sudden, a new possibility comes to mind. And so space and time need to be fluid, and space and time need to be rigid in order to come up with something meaningful. A- and I realize I'm riffing long on this, but this is why I think, you know, there was so much interest a few years ago with Michael Pollan's book and, and other things happening about psychedelics as a pathway to exploration and all this kind of thing. But the real question is what you export back from those experiences.

Lex Fridman 41:21 Right.

Andrew Huberman 41:22 Because dreams are amazing, but if you can't bring anything back from them, they're just amazing.

Lex Fridman 41:27 I wonder how to experiment with the mind without, without any medical assistance first. Like, you know, I, I push my mind in all kinds of directions. I definitely want to... I, I did, uh, shrooms a couple of times. I definitely want to, uh, figure out how I can experiment with, um, with psychedelics. I'm talking to, uh, Rick-... Domin, I think?

Andrew Huberman 41:52 No, it's Doblin.

Lex Fridman 41:53 Doblin. Uh, soon (laughs) I em- went back and forth. So he does all these studies in psychedelics, and he keeps ignoring the parts of my email that asks like, "How do I participate in these studies?" (laughs)

Andrew Huberman 42:04 Yeah. Well, there are some legality issues. I mean, the conversation... I wanna be very clear. I'm not saying that-

Lex Fridman 42:08 No.

Andrew Huberman 42:08 ... anyone should go out and do psychedelics.

Lex Fridman 42:10 No.

Andrew Huberman 42:10 I think that drowsy states and sleep states are, are super interesting for accessing some of these more creative states of mind. Hypnosis is something that my colleague, David Spiegel, Associate Chair of Psychiatry at Stanford, works on, where also, again, it's a unique state because you have narrow context. So this is very, um, kind of tunnel vision and yet, deep really rela- excuse me, deeply relaxed, where new algorithms, if you will, can start to surface. Um, strong state for inducing neuroplasticity. And I think the... You know, so if I had a, um... I'm part of a group, um, that, uh, it's called the Liminal Collective. It's a group of people that get together and talk about, um, just wild ideas, but they try and implement.

Lex Fridman 42:51 Yeah.

Andrew Huberman 42:51 Um, and it's a, it's a really interesting group. Some people from, uh, military, from, uh, Logitech, and some other backgrounds, academic backgrounds. And I was asked, you know, what would be... Um, if you could create a tool, if you just had a tool, like your magic wand wish for the day, what would it be? I thought it'd be really interesting if someone could develop psychedelics that have, um, on-off switches. So you could go into a psychedelic state very deeply for 10 minutes, but you could launch yourself out of that state and place yourself into a linear, real world state very quickly so that you could extract whatever it was that, that happened in that experience and then go back in if you wanted. Because the problem with psychedelic states and dream states is that, first of all, a lot of the reason people do them is they're lying. They say they want plasticity and they want all this stuff.

Lex Fridman 43:43 Mm-hmm.

Andrew Huberman 43:43 They want a peak experience-

Lex Fridman 43:45 Yeah.

Andrew Huberman 43:45 ... inside of an amplified experience. So they're kind of seeking something unusual.

Lex Fridman 43:50 Yeah.

Andrew Huberman 43:50 And I think we should just be honest about that.

Lex Fridman 43:51 Yep. Mm-hmm.

Andrew Huberman 43:51 Because a lot of times, they're not trying to make their brain better, they're just trying to experience something really amazing. But the problem is space and time are so unlocked in these states, just like they are in dreams, that you can really end up with a whole lot of nothing. You can have an amazing amplified experience housed in an a- amplified experience and come out of that thinking you had a meaningful experience when you didn't bring anything back.

Lex Fridman 44:18 You didn't bring anything back.

Andrew Huberman 44:19 Right.

Lex Fridman 44:19 All y- all you have is a fuzzy memory of having a transformational experience.

Andrew Huberman 44:25 Right.

Lex Fridman 44:25 But you don't actually have-

Andrew Huberman 44:26 It could be-

Lex Fridman 44:27 ... yeah, tools to bring back or I just-

Andrew Huberman 44:28 That's right.

Lex Fridman 44:29 Sorry, actual f- actually concrete ideas to bring back. Yeah, it's interesting. You shou- yeah, I wonder if it's possible to do that with the m- with the mind to, to be able to ho- hop back and forth, like-

Andrew Huberman 44:40 Well, I think that's where the real power of, you know, adjusting states is gonna be. It probably will be with devices. Um, I mean, maybe it'll be done through pharmacology. It's just that it's hard to do on-off switches in, in human pharmacology that we have them for animals. I mean, we ha- we have, you know, Cre-Flip recombinases, and we have, um, you know, channelopsins and halorhodopsins, and, um, all these kinds of things. But to, to do that work in humans is tricky, but I think you could do it with, um, virtual reality, augmented reality, and other devices that bring more of the somatic experience

Andrew Huberman 45:13 into it.

Lex Fridman 45:13 You're, of course, a scientist who's studying humans as a collective. I tend to be just a, a one person scientist of just looking at myself. And, you know, I play... When these deep thinking, deep work sessions, I'm very cognizant, like in the morning, that there's times when my mind is so, like, eloquent at being able to jump around from ideas and hold them all together. And I, I'm almost like I step back from a third person perspective and enjoy that, whatever that mind is doing. I'm, I do not waste those moments. I... And I'm very conscious of, um, this like little creature that woke up, that's only awake for, if we're being honest, maybe a couple hours a day. Uh, if-

Andrew Huberman 46:03 Early part of the day for you.

Lex Fridman 46:05 Early part of the day. Not always. Well, early part of the day for me is a very, uh, fluid concept. (laughs) So...

Andrew Huberman 46:11 You're one of those.

Lex Fridman 46:12 Yeah, I'm one.

Andrew Huberman 46:12 Yeah, you're one of those.

Lex Fridman 46:13 So, being single, one of the problems, single and no meetings, I don't schedule any meetings. I, I will... I've been living, uh, like a 28-hour day. So I just, I like, I, uh, it drifts. So it's, it's all over the fr- uh, the, the place. But after, uh, a, uh, traditionally defined full night sleep, (laughs) uh, whatever the heck that means, I, I find that like in, in those moments, there's a clarity of mind that's just... That's everything is effortless and it's the, it's the deepest dives intellectually that I make. And I, uh, I'm cognizant of it, and I try to bring that to the other parts of the day that don't have it and treasure them even more in those moments, 'cause they only last like 5 or 10 minutes. Uh, 'cause, of course, in those moments, you wanna do all kinds of stupid stuff that are completely is, is, is worthless, like check social media or something like that. But those are the most precious things in, in an i- in an intellectual life, is those mental moments of clarity. And I wonder... I'm learning how to control them. I think caffeine is somehow involved. I'm not sure exactly.

Andrew Huberman 47:22 Sure. Well, because if, if you learn how to titrate caffeine, and everyone's slightly different with this, uh, what they need, but if you learn to titrate caffeine with time of day and the kind of work that you're trying to do, you can bring that autonomic arousal state into a, the close to perfect place.

Lex Fridman 47:36 Yeah.

Andrew Huberman 47:36 And then you can tune it in with, you know... Sometimes people want a little bit of background music, sometimes they want less, these kinds of things. The, the, the early part of the day is interesting because the, um, one thing that's not often discussed is this transition out of sleep. So there's a, a book, um, I think it's called Winston Churchill's Nap, and it's about naps and, and the transition between wake and sleep as a valuable period. Um, I've...Uh, a long time ago, um, someone who I respect a lot was mentoring me, said, um, "Be very careful about bringing in someone else's sensory experience early in the day." So when I wake up, I'm very drowsy. I sleep well, but I, I don't emerge from that very quickly. I need a lot of caffeine to wake up and whatnot. But there's this concept of getting the download from sleep.

Lex Fridman 48:25 Mm-hmm.

Andrew Huberman 48:25 Which is, you know, in sleep, you're, uh, you were essentially expunging the things that you don't need.

Lex Fridman 48:30 Mm-hmm.

Andrew Huberman 48:30 The stuff that's meaningless from the previous day. But you were also running variations on these algorithms of whatever it is you're trying to work out in life on short timescales, like the previous day, and long timescales, like your whole life. (laughs) And those lateral connections in layer five of the, of the neocortex are very robustly, um, active and, uh, across sensory areas, and, and you're running a, an algorithm or a colle- you know, a brain, it's a brain state that would be useless and waking. You wouldn't get anything done. You'd be the person talking to yourself in the hallway or something about something that no one else can see. But in those states, you do the, the theory is that you arrive at certain solutions and those solutions will reveal themselves in the early part of the day.

Lex Fridman 49:12 Mm-hmm.

Andrew Huberman 49:12 Unless you interfere with them by bringing in, social media is a good example, of you immediately enter somebody else's spacetime sensory relationship. Someone is the conductor of your thoughts in that case. And so many people have written about this. Um, what I'm saying isn't entirely new, but, but allowing the download to occur in the early part of the day and, and asking the question, am I more in my head or external? Am I in more of an interoceptive or exteroceptive mode? And depending on the kind of work you need to do, if it's, it sounds like for you, it's very interoceptive in the end, very... you got a lot of thinking going on and a lot of computing going on. Allowing yourself to transition out of that sleep state and arrive with those solutions from sleep and plug into the work really deeply.

Lex Fridman 49:59 Oh, yeah.

Andrew Huberman 49:59 And then, and only then allowing things like music, news, social media, doesn't mean you shouldn't talk to loved ones and see faces and things like that, but some people have taken this to the extreme. When I was a graduate student at Berkeley, there was a guy, um, there was a professor, brilliant, odd, but brilliant, um, who was so fixated on this concept that he wouldn't look at faces in the early part of the day.

Lex Fridman 50:22 Mm-hmm.

Andrew Huberman 50:23 Because he just didn't want to, anything else to impact him. Now, he would, didn't have the most, um, rounded life, (laughs) I suppose. But if you're talking about, um, cognitive performance, this could be actually be very beneficial.

Lex Fridman 50:36 You said so many brilliant things. So one, if you read books that describe the habits of, um, brilliant people like, uh, writers, they do control their sensory experience in, in the w- in the, in the hours after wake. Like many writers, you know, they have a particular habit of several hours early in the morning of actual writing. They don't do, don't do any- anything else for the rest of the day, but they control, they're very sensitive to noises and so on. I think they make it very difficult to live with them. I try to... I'm definitely like that, like I could, I- I love to control the sensory, uh, how much information is, is coming in. There's something about the peaceful, just everything being peaceful. At the same time, and we were talking to a mutual friend of Whitney Cummings, who, um, has, has a, has a mansion, a castle on top of a cliff in, in the middle of nowhere. She actually purchased her own island. Uh, so she wants silence. She wants to control how much, uh, uh, s- sound is coming in.

Andrew Huberman 51:41 She's very sensitive to, to sound and environment.

Lex Fridman 51:44 Yeah.

Andrew Huberman 51:44 Yeah, beautiful home and environment, but like clearly puts a lot of attention into-

Lex Fridman 51:49 Just quiet.

Andrew Huberman 51:49 ... details, yeah. And, and very creative.

Lex Fridman 51:52 Yeah. And that's-

Andrew Huberman 51:53 Yeah.

Lex Fridman 51:53 Yeah, that allows for creativity to flourish. I'm also... I don't like, that feels like a slippery slope. So I, I enjoy introducing, uh, noises and signals and, uh, training my mind to be able to tune them out. 'Cause I feel like you can't always control the environment so perfectly because, uh, because your mind gets comfortable with that. I think it's a skill that you want to learn to be able to sh- shut it off. Like, I often go to like back before COVID to a coffee shop. It really annoys me when there's sounds and voices and so on, but I feel like I can train my mind-

Andrew Huberman 52:29 Mm-hmm.

Lex Fridman 52:29 ... to, to block them out. So it's, it's a balance, I think.

Andrew Huberman 52:32 Yeah, and I think, um, you know, two things come to mind, um, as you're saying this. Um, first of all, yeah, I mean, we're talking about what's best for work is not always what's best for, you know, completeness of life. I mean, you know, autism is probably many things, like when you hit autism, just like feet, there are probably 50 ways to get a fever. There are probably 50 ways to, that the brain can create what looks like autism or what people call autism. There's an interesting set of studies that have come out of David Ginti's lab at Harvard Med, um, looking at... These are mouse mutants where, um, these are models for autism where nothing is disrupted in the brain proper and in the central nervous system. But the sensory ap- the sensory neurons, the ones that innervate the skin and the ears and everything are, are hypersensitive. And this maps to a mutation in certain forms of human autism. So this means that the, the overload of sensory information and sensory experience that a lot of autistics feel, they're like that they can't tolerate things and then they get the stereotype behaviors, the rocking and the kind of like the shouting. It, you know, we always thought of that as a brain problem. In some cases it might be, but in many cases it's because they just can't to- they, they seem to have a m- It's like turning the volume up on every sense. And so they're overwhelmed. And none of us want to become like that. I think it's very hard for them and it's hard for their parents and so forth. So I, I like the, the coffee shop example because, um, the way I think about...... trying to build up resilience, uh, you know, physically or mentally or otherwise is one of, um, I guess we could call it lim- I like to call it limbic friction. That's not a real scientific term, and I acknowledge that. I'm making it up now because I think it captures the concept, which is that, you know, we always hear about resilience. It makes it sound like, oh, you know, under stress where everything's coming at you, you're gonna stay calm. But there's ano- you know, so limbic, the limbic system wants to pull you in some direction, typically in the direction of reflexive behavior, (laughs) and the prefrontal cortex, through top-down mechanisms, has to suppress that and say, "No, we're not gonna respond to the banging of the coffee cups behind me," or, "I'm gonna keep focusing." That's pure top-down control. So limbic friction is high in that environment. You've put yourself into a high limbic friction environment, meaning that the prefrontal cortex has to work really hard. But there's another side to limbic friction too, which is when you're very sleepy. There's nothing incoming. It can be completely silent, and it's hard to engage in focus because you're drifting off, and you're getting sleepy. So their limbic friction is high but for the opposite reason, autonomic arousal is too low. So they're turning on Netflix in the background or looping a song might boost your level of alertness that will allow top-down control to be in, in the pla- exactly the sweet spot you want it. So the, this is why earlier I was saying it's all about how we feel inside relative to what's going on on the outside. We're constantly in this... Uh, I guess one way you could envision it spatially, especially if, uh, people are listening to this just on audio, is, I like to think about it kind of like a glass barbell, where one sphere of perception and attention can be on what's going on with me, and one sphere of attention can be on what's going on with you or something else in the room or in my environment. But those, this barbell isn't rigid. It's not really glass. Would plasma work here? I don't know anything about plasma.

Lex Fridman 55:52 (laughs)

Andrew Huberman 55:53 (laughs) Sorry, I don't know.

Lex Fridman 55:54 Yeah, yeah.

Andrew Huberman 55:54 Okay. But, so imagine...

Lex Fridman 55:56 Yeah.

Andrew Huberman 55:56 ... that this thing can contort. The size of the, the, the globes at the end of this barbell can get bigger or smaller. So let's say I close my eyes, and I bring all my experience into what's going on inter- in- through interoception internally. Now, it's as if I've got two orbs of perception just on my internal state. But I can also do the opposite and bring two, both orbs of perception outside me. I'm not thinking about my heart rate or my breathing. I'm just thinking about something I see. And what you'll start to realize as we kind of use this spatial model is that two things. One is that it's very dynamic and that the more relaxed we are, the more these two orbs of attention, the two ends of the barbell, can move around freely.

Lex Fridman 56:37 I see.

Andrew Huberman 56:38 The more alert we are, the more rigid they're gonna be tethered in place. And that was designed so that if I have a threat in my environment, it's tethered to that threat. I'm not gonna be, if something's coming to attack me, I'm not gonna be like, "Oh, my breathing cadence is a little bit quick." That's not how it works. Why? Because both orbs are linked to that, uh, to that threat. And so my behavior is now actually being driven by something external, even though I think it's internal. And so I don't wanna get too abstract here because I'm a neuroscientist, I'm not a, a theorist, but when you start thinking about models of how the brain work, I mean, brain works, excuse me, there are only really three things that neurons do. They're either sensory neurons, they're motor neurons, or they're modulating things. And th- the models of attention and perception that we have now, 2020, tell us that we've got interoception and exteroception. They're strongly modulated by levels of autonomic arousal, and that if we want to form the optimal relationship to some task, or some pressure, or something, whether or not it's sleep, an impending threat, or coding, we need to adjust our internal spacetime relationship with the external spacetime relationship. And I realize I'm repeating what I said earlier. But we can actually assign circuitry to this stuff. It mostly has to do with how much limbic friction there is, how much you're being pulled to some source. That source could be internal. If I have, if I have pain, physical pain in my body, I'm gonna be much more interoceptive than I am exteroceptive. You could be talking to me, and I'm just gonna be thinking about that pain. It's very hard. And the other thing that we can link it to is top-down control, meaning anything in our environment that has a lot of salience will tend to bring us into more exteroception than interoception. And again, I don't wanna litter the conversation with just a bunch of terms, but, um, what I think it can be useful for people is to do what essentially you've done, Lex, is to start developing an awareness. When I wake up, am I mostly in a mode of interoception or exteroception? When I work well, is that... What does working well look like from the perspective of autonomic arousal? How alert or calm I- am I? What kind of balance between internal focus and external focus is there?

Lex Fridman 58:50 C- can you-

Andrew Huberman 58:50 And to sort of watch this process throughout

Andrew Huberman 58:53 the day, yeah.

Lex Fridman 58:53 C- can you linger just briefly on, 'cause you use this term a, a lot, and it'd be nice to try to get a little more color to it, which is interoception and exteroception, uh, wha- uh, what are we, what are we exactly talking about? So like, what's included in each category and how much overlap is there?

Andrew Huberman 59:12 Interoception would be, uh, an awareness of anything that's within the confines or on the surface of my skin that I'm sensing.

Lex Fridman 59:20 Oh, so literally physiological, like-

Andrew Huberman 59:21 Physiological, like within the boundaries of my skin and probably touch to the skin as well. Exteroception would be perception of anything that's ex- beyond the reach of my skin, so the, that bottle of water, um, a, a scent, um, a sound, although it... And this can change dramatically actually. If you have headphones in, you tend to hear things in your head if-

Lex Fridman 59:44 Mm-hmm.

Andrew Huberman 59:45 ... as opposed to a speaker in the room.

Lex Fridman 59:46 It's interesting, yeah.

Andrew Huberman 59:47 This is actually the basis of ventriloquism. So there are beautiful experiments done by Gregg Rechenzon up at UC Davis looking at how auditory and visual cues are matched, and we have an array of speakers, and you can, uh, this will become obvious as I say it, but, you know, obviously, the ventriloquist doesn't throw their voice. What they do is they direct your vision to a particular location, and you think the sound is coming from that location.

Lex Fridman 1:00:09 Yeah.

Andrew Huberman 1:00:10 And there are beautiful experiments that Gregg and his colleagues have done where they suddenly introduce a auditory visual mismatch, and it freaks people out because you can actually make it seem, from a perception standpoint, as if the sound arrived from the corner of the room and hit you, like, i- physically.

Lex Fridman 1:00:26 Mm-hmm.

Andrew Huberman 1:00:26 And, and people will recoil. And so sounds aren't getting thrown across the room. They're still coming from this defined location, an array of speakers, but this is the way the brain creates these internal representations and-... again, not to, I don't wanna go down a rabbit hole, but, um, I think as much as you're, you know, I'm sure the listeners appreciate this, but, you know, everything in the brain is an abstraction, right? I mean, they're, they're... The sensory apparati, they are the eyes and ears and nose and skin and taste and all that, are taking information, and with interoception, it's taking information from sensors inside the body, the enteric nervous system for the gut. I've got, uh, sensory neurons that inner make my liver, um, et cetera, taking all that, and the brain is abstracting that in the same way that if I took a picture of your face and I handed it to you and I'd say, "That's you," you'd say, "Yeah, that's me." But if I were an abstract artist, I'd be doing a little bit more what the brain does, where if I took a pen and... pad and paper, maybe I could do this 'cause I'm a terrible artist, and I could just mix it up and I'd, let's say I would make your eyes like water bottles, but I'd flip them upside down, and I'd start assigning fruits and objects to the different features...

Lex Fridman 1:01:38 Yeah.

Andrew Huberman 1:01:38 ... of your face and I showed it to you, I'd say, "Lex, that's you," you'd say, "Well, that's not me," and I'd say, "No, but that's my abstraction of you."

Lex Fridman 1:01:42 Mm-hmm.

Andrew Huberman 1:01:42 But that's what the brain does. The spacetime relationship of the neurons that fire that encode your face hasn't... have no resemblance to your face.

Lex Fridman 1:01:51 Right. And then they, they form the...

Andrew Huberman 1:01:52 (laughs) And I think people don't really, uh, I don't know if people have fully internalized that, but the day...

Lex Fridman 1:01:56 Of course.

Andrew Huberman 1:01:56 ... that I... And I'm not sure I fully internalized that because it's weird to think about, but all neurons can do is fire in space and in time. Different neurons in different sequences, perhaps with different intensities.

Lex Fridman 1:02:08 Mm-hmm.

Andrew Huberman 1:02:08 It's not clear the action potential is all or none, although people, neuroscientists don't like to talk about that even though it's been published in Nature a couple of times. The action potential for a given neuron doesn't always have the exact same waveform. People...

Lex Fridman 1:02:20 Oh, interesting.

Andrew Huberman 1:02:20 It's in all the textbooks, but you can modify that waveform.

Lex Fridman 1:02:23 Well, the, the, uh... (laughs) I mean, there's a lot of fascinating stuff with, uh, with neuroscience about the fuzziness of all the, uh, uh, o- of the transfer of information from neuron to neuron. I mean, the, we, we certainly touch upon it every time we at all try to think about the difference between artificial neural networks and biological neural networks. But can we, uh, maybe linger a little bit on this, uh, on this circuitry that you're getting at? So the brain is just a bunch of stuff firing and it forms abstractions that are fascinating and beautiful, like layers upon layers upon layers of abstraction. And I think it, uh, just like when you're programming, you know, I'm programming in Python, it's, uh, it's awe-inspiring to think that underneath it all, it ends up being zeros and ones. And the computer doesn't know about those stupid Python or Windows or Linux. It, it only knows about the zeros and ones. In the same way with the brain, is there something interesting to you or fundamental to you about the circuitry of the brain that allows for the magic that's in our mind to emerge? How much do we understand, I mean, maybe even focusing on the vision system, is, is there something specific about the structure of the vision system, the circuitry of it, that, uh, allows for the complexity of the vision system to emerge? Or is it all just a complete chaotic mess that we don't understand?

Andrew Huberman 1:03:53 It's definitely not all a chaotic mess that we don't understand, if we're talking about vision. (laughs)

Lex Fridman 1:03:58 (laughs) Okay, let's stick-

Andrew Huberman 1:03:59 And that's not just 'cause I'm a vision scientist, but...

Lex Fridman 1:04:01 Let's stick to vision as well.

Andrew Huberman 1:04:02 Let's stick to vision. Well, because in... the beauty of the visual system, the reason David Hubel and Torsten Wiesel won the Nobel Prize was because they were brilliant and forward-thinking and adventurous and all that good stuff. But the reason that the visual system is such a great model for addressing these kinds of questions and other systems are hard, is we can control the stimuli.

Lex Fridman 1:04:20 Mm-hmm.

Andrew Huberman 1:04:20 We can adjust spatial frequency, how fine or... the gratings are, thick gratings, thin gratings. We can adjust temporal frequency, how fast things are moving. We can, um, use cone isolating stimuli. We can use... There's so many things that you can do in a controlled way. Whereas if we're talking about cognitive encoding...

Lex Fridman 1:04:36 Right.

Andrew Huberman 1:04:37 ... like the, uh, you know, encoding the space of concepts or something.

Lex Fridman 1:04:40 Right.

Andrew Huberman 1:04:41 You know, I, I, I've...

Lex Fridman 1:04:42 (laughs)

Andrew Huberman 1:04:43 You know, I, like you, uh, if I may, are dr- am drawn to the, the big questions...

Lex Fridman 1:04:48 Yes.

Andrew Huberman 1:04:48 ... in neuroscience. But I confess, in part because of some good advice I got early in my career, and in part because I'm, um, not s- perhaps smart enough to go after the really high level stuff, I also like to address things that are tractable and I want, you know, we need to, we need to address what we can stand to make some ground on at a given time. Now-

Lex Fridman 1:05:13 Is they construct brilliant controlled experiments to s- to study, to really literally answer questions about, yeah.

Andrew Huberman 1:05:20 Yeah, I mean, I'm happy to have a talk about consciousness, but it's, uh, it's a scary th- talk and I'm, I think most people don't wanna hear (laughs) what I have to say. Which is, you know, which is, uh, we can save that for later perhaps, or another day, but...

Lex Fridman 1:05:30 I mean, the, what, it'd be, it's an interesting question of, uh, we talk about psychedelics, we can talk about consciousness, we can talk about cognition, can experiments in neuroscience be constructed to shed any kind of light on these questions? So I mean, it's cool that vision... I mean, to me, vision is probably one of the most beautiful things about human beings. Uh, also, uh, from the AI side, computer vision has some, has some of the most exciting applications of, uh, neural networks is in computer vision. But it feels like that's a, that's a neighbor of cognition and consciousness.

Andrew Huberman 1:06:08 Mm-hmm.

Lex Fridman 1:06:08 It's just that we maybe haven't come up with experiments to study

Lex Fridman 1:06:11 those yet.

Andrew Huberman 1:06:11 Yeah, the visual system is amazing. We're mostly visual animals. To navigate, t- survive, humans mainly rely on vision, not smell or something else. But, um, it's a filter for cognition, and it's a, it's a strong driver of cognition. M- maybe just 'cause it came up and then, uh, we're moving to higher level concepts. I just... The, the way the visual system works can be summarized in a, um, in a few relatively succinct statements, unlike most of what I've said, which has not been succinct at all.

Lex Fridman 1:06:39 Let's go there. What, uh, what-

Andrew Huberman 1:06:40 You know, the, the retina...

Lex Fridman 1:06:41 ... what's, what's involved?

Andrew Huberman 1:06:42 Yeah, so the retina is this-... three layers of neuron structure at the back of your eye, it's about as thick as a credit card. It is a piece of your brain, and sometimes people think I'm kind of wriggling by, out of, uh, reality by saying that. It is, it's absolutely a piece of the brain, it's- it's a forebrain structure that in the first trimester, there's a genetic program that made sure that that neural retina, which is part of your central nervous system, was squeezed out into what's called the embryonic eye cups, and that the bone formed with a little hole where the optic nerve is gonna connect it to the rest of the brain. And those, that window, uh, into the world is the only window into the world for a, for a mammal which has a thick skull. Birds have a thin skull, so their pineal gland sits... And lizards too, and snakes actually have a hole so that light can make it down into the pineal directly and then train melatonin rhythms for time of day and time of year. Humans have to do all that through the eyes. So three layers of neurons that are a piece of your brain, they are a central nervous system, and the optic nerve connects to the rest of the brain. The neurons in the eye, some just care about luminance, just how bright or dim it is...

Narrator 1:07:48 Mm-hmm.

Andrew Huberman 1:07:48 ... and they inform the brain about time of day, and then the central circadian clock informs every cell in your body about time of day and makes sure that all sorts of good stuff happens if you're getting light in your eyes at the right times.

Narrator 1:07:57 Mm-hmm.

Andrew Huberman 1:07:57 And all sorts of bad things happen if you are getting light randomly throughout the 24-hour cycle. We could talk about all that, but this is a good incentive for keeping a relatively normal schedule, a consistent schedule...

Narrator 1:08:08 You lost me.

Andrew Huberman 1:08:09 ... of light exposure.

Narrator 1:08:09 (laughs)

Andrew Huberman 1:08:10 Con- consistent schedule.

Narrator 1:08:11 Okay.

Andrew Huberman 1:08:12 Try and keep a consistent schedule. When you're young, it's easy to go off schedule and recover. As you get older, it gets harder, but you see everything from outcomes in cancer patients to, oh, um, diabetes in, um, you know, improves when people are getting light at a particular time of day and getting darkness at a particular phase of the 24-hour cycle. We were des- designed to, um, get light and dark at different times of the c- of the circadian cycle. That's all being, all that information is coming in through a specialized type of neuron in the retina called the melanopsin, an intrinsically photosensitive ganglion cell discovered by David Berson at Brown University. That's not spatial information, it's subconscious, you don't think, "Oh, it's t- daytime." Even if you're looking at the sun, it doesn't matter, it's a photon counter. It's literally counting photons. And it's saying, "Oh, even though it's a cloudy day, lots of photons coming in. Ah, it's winter in Boston, it must be winter," and your system is a little depressed. It's spring and you feel alert. That's not a coincidence. That's these melanopsin cells signaling the circadian clock. There are a bunch of other neurons in the eye that signal to the brain, and they mainly signal the presence of things that are lighter than background or darker than background. So a black object would be darker than background, a light object, lighter than background, and that all com- it's mainly a pi- it's looking at pixels, mainly, it's loo- they look at circles, and those neurons have receptive fields, which not everyone will understand, but those neurons respond best to little circles of dark light or little circles of bright light.

Narrator 1:09:40 Mm-hmm.

Andrew Huberman 1:09:40 Little circles of red light versus l- little circles of green light or blue light. And so it sounds very basic, it's like, red, green, blue, and circles, brighter or dimmer than what's next to it, but that's basically the only information that's sent down the optic nerve.

Narrator 1:09:57 Mm-hmm.

Andrew Huberman 1:09:57 And when we say information, we can be very precise. I don't mean little bits of red traveling down the optic nerve, I mean spikes, neural action potentials...

Narrator 1:10:05 Mm-hmm.

Andrew Huberman 1:10:05 ... in space and time, which for you is like makes total sense, but I think for a lot of people, it's, uh, it's actually beautiful to think about. All that information in the outside world is converted into a language that's very simple, it's just like a few syllables, if you will.

Narrator 1:10:20 Mm-hmm.

Andrew Huberman 1:10:21 And those syllables are being shouted down the optic nerve, converted into a totally different language like Morse code.

Narrator 1:10:27 Mm-hmm.

Andrew Huberman 1:10:27 Beep, beep, beep, beep, beep.

Narrator 1:10:28 Yeah.

Andrew Huberman 1:10:28 Goes into the brain, and then the thalamus essentially responds in the same way that the retina does, except the thalamus is also weighting things. It's saying, "You know what? That thing, um, was moving faster than everything else, or it's brighter than everything else, so that signal, I'm gonna get up, I'm gonna allow up to cortex." Or, "That signal is much redder than it is green, so I'm gonna let that signal go through. That signal is much, eh, it's kind of more like the red next to it, throw that out."

Narrator 1:10:58 Mm-hmm.

Andrew Huberman 1:10:58 The information just doesn't get up into your cortex. And then in cortex, of course, is where perceptions happen, and in V1, if you will, visual area one, but also some neighboring areas, you start getting representations of things like oriented lines. So there is a neuron that responds to this angle of my hand versus vertical.

Narrator 1:11:16 Mm-hmm.

Andrew Huberman 1:11:16 Right? This is the defining work of Hubel and Wiesel's Nobel, and it's a very systematic map of orientation, line orientation, direction of movement, and so forth. And that's pretty much, and color, and that's how the visual system is organized all the way up to the cortex. So it's hierarchical. You don't build... I wanna be clear, it's hierarchical because you don't build up that line by suddenly having a neuron that responds to lines...

Narrator 1:11:40 Mm-hmm.

Andrew Huberman 1:11:41 ... in a some random way. It responds to lines by taking all the dots that are aligned in a vertical stack, and they all converge on one neuron, and then that neuron responds to vertical lines. So it's not random. There's no abstraction at that point, in fact. In fact, if I showed you a black line, I could be sure that if I were imaging V1, that I would see a representation of that black line as a vertical line somewhere in, in your cortex. So at that point, uh, it's absolutely concrete, it's not abstract.

Narrator 1:12:11 Mm-hmm.

Andrew Huberman 1:12:11 But then things get really mysterious. Some of that information travels further up into the cortex, so that, and goes from one visual area to the next, to the next, to the next, so that by the time you get into an area that, um, Nancy Kanwisher at MIT has studied her, much of her career, the fusiform face area, you sa- start finding single neurons that respond only to your father's face, or to Joe Rogan's face, regardless of the orientation of his face. I'm sure if you saw Joe, 'cause you know him well, from across the room and you just saw his profile, you'd be like, "Oh, that's Joe. I'm gonna walk over and say hello."... the orientation of his face isn't there, you wouldn't even see his eyes necessarily, but he's represented in some abstract way by a neuron...

Narrator 1:12:56 Mm-hmm.

Andrew Huberman 1:12:56 ... that actually would be called the Joe Rogan neuron, or a collection of neurons.

Narrator 1:12:59 It might, it might have limits, like I might not recognize him if he was upside down or something like that. It'd be fascinating to, to see what the limits of that Joe Rogan concept is.

Andrew Huberman 1:13:08 So Nancy's lab has done that, because early on, she was challenged by people that said, "There aren't face neurons."

Narrator 1:13:14 Right.

Andrew Huberman 1:13:14 There are neurons that they only respond to space and time, shapes and things like that, moving in particular directions and orientations. And it turns out Sh- Nancy was right. Um, they used the stimuli called Grebel stimuli, which, um, any computer programmer would appreciate, which kind of morphs a face into something gradually that eventually just looks like this, like, alien thing they call the Grebel.

Narrator 1:13:34 Mm-hmm.

Andrew Huberman 1:13:35 And the neurons don't respond to Grebels, in most cases they only respond to faces and familiar faces. Anyway, I'm summarizing a lot of literature, and forgive me Nancy, and for those of the Grebel people, if there are anything, like, don't come after me with pitchforks.

Narrator 1:13:48 (laughs) Yeah.

Andrew Huberman 1:13:48 If you come... Actually, you know what? Come after me with pitchforks.

Narrator 1:13:50 (laughs)

Andrew Huberman 1:13:50 I think you know what I'm trying to do here.

Narrator 1:13:51 Yeah.

Andrew Huberman 1:13:52 So the point is that in the visual system, it's very concrete up until about visual area four, which has color pinwheels and seems to respond to pinwheels of colors. And, um, and so the stimuli become more and more elaborate, but at some point, you depart that concrete representation and you start getting abstract representations that can't be explained by simple point-to-point wiring.

Narrator 1:14:15 Mm-hmm.

Andrew Huberman 1:14:16 And to take a leap out of the visual system to the higher level concepts, what we talked about in the visual system maps to the auditory system where you're encoding, what? Frequency of tone, sweeps.

Narrator 1:14:28 Mm-hmm.

Andrew Huberman 1:14:28 So this is gonna sound weird to do, but you know, uh, like a doppler, like hearing something, a car passing by, for instance. But at some point, you get into motifs of music that can't be mapped to just a, a, a, what they call a tonotopic map, a frequency. You start abstracting. And if you start thinking about concepts of creativity and love and memory, like, what is the map of memory space?

Narrator 1:14:52 Right.

Andrew Huberman 1:14:52 Well, your memories are very different than mine, but presumably there's enough structure at the early stages of memory processing, or at the early stages of emotional processing, or at the earlier stages of creative processing, that you have the building blocks, your zeros and ones, if you will, but you depart from that eventually. Now, the exception to this, and I wanna be really clear, 'cause I was just mainly talking about neocortex, the six layered structure on the outside of the brain that explains a lot of human abilities, other animals have them too, is that subcortical structures are a lot more like machines. It's more plung and chug. And what I'm talking about is the machinery that controls heart rate and breathing and receptive fields, um, you know, neurons that respond to things like temperature on the top of my left hand. And one of the... You know, I came into neuroscience from a more of a perspective o- initially of psychology, but one of the reasons I forced upon myself to learn some electrophysiology, not a ton, but enough, and some molecular biology and about circuitry, is that one of the most beautiful experiences you can have in life, I'm convinced, is to lower an electrode into the cortex and to show a person or an animal, you do this ethically of course, a stimulus...

Narrator 1:16:15 Yes.

Andrew Huberman 1:16:16 ... like an oriented line or a face, and you he- can convert the recordings coming off of that electrode into an audio signal, an audio monitor, and you can hear what they call hash. It's not the hash you smoke, it's the hash you hear. And it's, it sounds like... (hissing) It just sounds like noise.

Narrator 1:16:32 Mm-hmm.

Andrew Huberman 1:16:33 And in the cortex, eventually you find a stimulus that gets the neuron to spike and fire action potentials that are converted into an auditory stimulus that are very concrete. Crack, crack, crack. Sounds like a bat cracking, you know, like home runs, you know, or, or outfield balls. When you drop electrodes deeper into the thalamus or into the hypothalamus or into the brain stem areas that control breathing, it's like a machine. You never hear hash. You drop the electrode down, this could be like a te- like a grungy old tungsten electrode...

Narrator 1:17:05 Mm-hmm.

Andrew Huberman 1:17:05 ... not high fidelity electrode, as long as it's got a little bit of insulation on it, you plug it into an audio monitor, it's picking up electricity, and if it's a visual neuron and it's in the thalamus or the retina and you walk in front of that animal or person, that-

Narrator 1:17:17 Mm-hmm.

Andrew Huberman 1:17:17 ... that neuron goes... (hissing) And then you walk away and it stops. And you put your hand in front of the eye again and it goes... (hissing) And you could do that for two days and that neuron will just, every time there's a stimulus, it fires. So whereas before it's a question of how much information is getting up to cortex and then these abstractions happening where you're creating these ideas. When you go subcortical, everything is...

Narrator 1:17:44 There's no abstractions.

Andrew Huberman 1:17:45 It's two plus two equals four.

Narrator 1:17:46 (laughing)

Andrew Huberman 1:17:47 There's no abstractions.

Narrator 1:17:48 Yeah.

Andrew Huberman 1:17:48 And this is why I, um, you know, I know we have some common friends at Neuralink, and I love the demonstration they did recently, I'm a huge fan of what they're doing and, and where they're headed. And no, I don't get paid to say that, and I have no, uh, you know, business relationship to them. I'm just a huge fan of the people and the mission. But my question was to some of them, you know, when are you gonna go subcortical? 'Cause if you want to control an animal, you don't do it in the cortex. The cortex is like the abstract painting I made of your face. It, stim, moving, removing one piece or changing something may or may not matter for the abstraction, but when you are in the subcortical areas of the brain, a stimulating electrode can evoke an entire behavior or an entire state. And so the brain, if we're gonna have a discussion about the brain and how the brain works, we need to really be clear which brain, because everyone loves neocortex. It's like, oh, canonical circuits and cortex, we're gonna get the cortical connectome. And sure, necessary, but not sufficient, not to be able to plug in patterns of electrical stimulation and get behavior. Eventually we'll get there. But if you're talking subcortical circuits, that's where the action is, that's where you could potentially cure Parkinson's by stimulating the subthalamic nucleus, because we know that it gates motor activation patterns in very predictable ways. So I think for those that are interested in neuroscience, it pays to pay attention to, like, is this a circuit that ab- abstracts the sensory