Chapter 1: What is the significance of neuroplasticity in learning?
Oftentimes people will ask me, like an older person will say, hey, I do crossword puzzles. Is that good? Yeah, it's good until you get good at it and then stop and do something that you're not good at and constantly find the next thing that's a real challenge for you. That's the key thing about plasticity. Your brain is locked in silence and darkness.
It's trying to make a model of the outside world. And if you're constantly pushing and challenging it with things it doesn't understand, then it'll keep changing.
Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. David Eagleman. Dr. David Eagleman is a neuroscientist, a bestselling author, and a longtime science public educator.
Today, we discuss several different features of brain science that impact your everyday life. And once you understand the mechanisms behind these features, it will position you to make better decisions, and if you choose, to rewire your brain to be a more effective learner.
We start by discussing neuroplasticity, which is your brain's ability to change in response to experience or any form of deliberate learning that you are trying to impose on yourself. We talk about the mechanisms for it and how you can get better at learning and unlearning in the context of skills and information.
We also discuss memory formation and the relationship between stress and time perception and why it is that people experience things in slow motion if those things are very stressful or traumatic and how that can be useful for undoing traumatic memories. David also takes us through the neuroscience of cultural and political polarization, something that's very timely right now.
False memories, deja vu, dreams, and the meaning of dreams, and a lot more. David is an absolutely legendary science communicator. I say this as a fellow neuroscientist. He is able to embed factual information about the brain into real life stories. And in doing so, he's able to shed light on how we work as humans and how we can all improve our life experience.
He's a true virtuoso of neuroscience and science education more generally. What David shares with us today will change the way that you think about thinking and your own mind, and no doubt will also change the way that you view the world. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford.
It is, however, part of my desire and effort to bring zero cost to consumer information about science and science related tools to the general public. In keeping with that theme, today's episode does include sponsors. And now for my discussion with Dr. David Eagleman. Dr. David Eagleman. Welcome. Thanks. Great to see you, Andrew.
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Chapter 2: How can we leverage neuroplasticity for better learning outcomes?
That's why we have 60, we've gotten off the planet. We build skyscrapers and compose symphonies and so on because we Each generation, we land and we get to spend our first few years absorbing everything that's been discovered before us.
And then we springboard off of that and do something new because we are able to figure out all the discoveries that have come before us because of this ability to reconfigure our own circuitry. And, you know, if you were a... An alligator born 30,000 years ago, you'd be the same alligator, you know, eat, mate, swim, whatever, and you wouldn't be meaningfully different.
But humans, because of our flexibility, we are the dominant species.
Such an interesting take on time and human evolution that, and I completely agree with you, I just had never thought about it this way before, that we land when we're born and we're absorbing the energy outcroppings of all the neuroplasticity that came before us.
We often hear that, you know, that the human brain is kind of like a macaque monkey brain with a supercomputer added on top of it, mostly the prefrontal cortex, a bit more prefrontal cortex, prefrontal cortex, prefrontal cortex.
We hear so- in general. Interesting. We have four times as much cortex as our nearest neighbors in the animal kingdom. And that seems to be the magical stuff.
Not just prefrontal cortex. Right.
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Chapter 3: What role does memory play in our perception of time?
And I'm sure the listenership knows this, but, you know, the cortex is just the outer three millimeters of the brain. It's that wrinkly bit. And that's the magic stuff because it turns out cortex is a one trick pony. The reason the cortex looks the same everywhere is because it is the same. It's got the same circuitry. It's got six little layers. It's doing the same algorithms.
And it gets defined by what you plug into it. So if you plug in a cable that's carrying visual information... then it becomes visual cortex. And we look at it and we say, oh, look, it detects the orientation of lines and it detects motion, things like that. If you plug auditory information into it, it becomes auditory cortex and so on.
And it turns out, you know, the way we do this in textbooks is we make a picture and we say, look, that's visual cortex, that's auditory, that's somatosensory. But
Chapter 4: How does cultural and personal experience shape our brain's plasticity?
All this stuff is really flexible. It's so much more interesting than the textbook model because you can take the fibers and plug them in somewhere else. So you may know the study in 2000 by Murgonkasor at MIT where he, in a ferret, took the visual ā information, the optic nerve, and he plugged it into the auditory cortex.
And then what would have been the auditory cortex became visually responsive, and it started caring about vision. So what does that mean? It means the cortex is a one-trick pony, and we got so much more of it, including the prefrontal cortex. So that has two major effects. One is that there's a lot more room with our species in between input and output.
So with a squirrel or a cat or even a macaque monkey, you know, you throw some food in front of it, that sensory cortex is right next to the motor cortex. It's going to eat the thing. But we've got all this computational real estate in between in and out. So we can say, well, I'm on a diet. I'm trying whatever. I'll eat it later. We've got all these other options that we can take.
That's one thing. And then the other thing is exactly what you pointed to, which is the prefrontal cortex, which allows us to simulate what ifs. Allows us to think about possible futures, simulate things in a way that we don't have to risk our lives doing it. We can simulate it and say, oh, that would be a bad idea. Oh, that'd be a pretty good idea. And then we can take the action.
A couple different questions. I'm a big fan of McGronk's work, and I'm so glad you mentioned that work. It really points to the fact that. While there are cortical areas that are genetically devoted by virtue of wiring when we arrive in the world to auditory or visual, that there's a lot of crossover, especially in the extreme cases.
So my understanding, correct me if I'm wrong, is that if somebody is blind from birth, the real estate that would be allocated to vision becomes allocated to vision. Tactile sensation, especially if they learn how to Braille read, maybe auditory processing because they rely on it more. So there's really no blank real estate in the cortex. It's all used.
That is exactly right. So it turns out, you know, right, people who are born blind, what we call the visual cortex in the back of the head here, That gets taken over. It's no longer visual. It becomes devoted to hearing, to touch, to memory, things like this. And you can demonstrate that people who are born blind are better at hearing and at touch and so on.
They can discriminate things much more finely. Same with people who go deaf. The auditory cortex, all that real estate, nothing lies fallow in the brain. All that gets taken over for different tasks and they can do things like see your accent, you know, just by lip reading, they can tell where in the country you're from and so on.
All of this demonstrates that, first of all, the more real estate you have, the better. We are, in a sense, if you've got all your senses, you have to share everything. And so we're pretty good at vision and hearing and touch and so on, but everything has to get shared. But there are pretty extraordinary things that happen when people devote more real estate towards one task.
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Chapter 5: Why does time perception change as we age?
Okay, fine. I guess that was really fast.
So this is why time speeds up as we grow older. Lingo helps me track my glucose in real time to see how the foods I eat and the actions I take impact my glucose. When glucose in your body spikes or crashes, your cognitive and physical performance do too.
Chapter 6: How do glucose levels affect cognitive performance?
In fact, large glucose peaks and valleys lead to brain fog, fatigue, irritability, and hunger. What you eat, of course, plays a major role in your glucose. Some foods cause sharp spikes and big crashes and others do not. But not everyone is the same in terms of how they respond to particular foods.
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Chapter 7: What role does memory density play in stressful situations?
It is not intended for the diagnosis of diseases, including diabetes. Individual responses may vary. I mean, I feel like these are what you're covering today is like the most interesting things about life and experience. I have a question about the fall experiment. Is it accurate to say that your perceptual frame rate during a highly stressful experience is not different.
You're not taking a higher frame rate movie, which is more frame rate is how they generate slow motion, for instance, makes sense, as opposed to strobe frame rate, right? but that in some sense your unconscious frame rate is because the amygdala is tracking more information than you normally would have access to in say a calm everyday experience.
And so the memory is higher frame rate, but the experience is not.
You know, it's really close. I wouldn't say I wouldn't use the term frame rate in there. It's just that you have under normal circumstances, you write down almost nothing. You just everything's passing through. You're not really remembering much. But in an emergency situation, your amygdala being the emergency control center says, everybody stop what you're doing.
Chapter 8: How can we combat polarization in society?
This is the most important thing going on. Everyone pay attention to this. So you're noticing every detail and you're not used to that. So just for anyone who knows what I'm referring to here as a Bayesian issue. you know, your brain thinks, okay, a certain amount of memory must equal a certain amount of time. Now you've got just a lot more detail.
And so it says, oh, well, that must have been, you know, six seconds or something. What I did, by the way, I collected hundreds and hundreds of subjective reports from people who had been in accidents of various sorts. You know, this guy got in a motorcycle accident and had, you know, come off the motorcycle and turned over and over and over on the road.
And he said, as he was rolling over and over, he was like composing a little ditty in his head, like a little song to the sound of his helmet hitting the road and so on, because this is the kind of bizarre thought that people have.
But it seemed to have taken a long time, and when he saw footage of it afterwards, you know, the whole thing took whatever, a second or two, but it seemed to him to have taken six seconds. But again, it's in retrospect when he's thinking, what happened? What was the event like?
By the way, I'll just mention after I published this paper, sometimes people would come up to me after a talk and say, I know that's not true because I was in a car accident. I know it took a long time. And I said, OK, look, the person on the passenger seat next to you who was screaming, no, did it actually sound like they were saying no?
Because if time were running in slow motion, that has to be the consequence that everything is spread out. And they had to allow that it didn't sound like sounds were distorted and so on. So it is really about having a higher density of memory.
Super interesting. What about for non-stressful, non-life-threatening circumstances? Like, let's pick a purely happy event.
Yes, yes.
One would hope, day of one's wedding. Yeah. I was about to say birth of a child, but depending on who's doing the majority of the work and how stressful it was, I mean, of course, the birth of a healthy child is a super wonderful event, but it can be very stressful too under certain circumstances. So let's pick something purely happy, right? Yeah.
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