A (6:11)
As I mentioned last episode, and I'll just tell you right now, again, the brain is incredibly plastic. From about birth until about age 25, and then somewhere about 25. It's not like the day after your 26th birthday. Plasticity closes. There's a tapering off of plasticity, and you need different mechanisms to engage plasticity. As an adult, knowing how to tap into these plasticity mechanisms is very powerful. The simplest example is if I hear something off to my right, I look to my right. If I hear it on the left, I look to my left. If I hear it right in front of me, I keep looking right in front of me. And that's because our maps of visual space and our maps of auditory space and our maps of motor space are aligned to one another in perfect register. It's an incredible feature of our nervous system. It takes place in a structure called the superior colliculus. Although you don't need to know that name. Superior colliculus has layers, literally stacks of neurons, like in a sandwich, where the zero point right in front of me, or maybe, you know, 10 or 15 degrees off to my right or 10 or 15 degrees off to my left, are aligned so that the auditory neurons, the ones that care about sounds at 15 degrees to my right, sit directly below the neurons that look at 15 degrees to my right in my visual system. And when I reach over to this direction, there's a signal that's sent down through those layers that says 15 degrees off to the right is the direction to look, it's the direction to listen, and it's the direction to move If I need to move, so there's an alignment. And this is really powerful. And this is what allows us to move through space and function in our lives in a really fluid way. It's set up during development, but there have been some important experiments that have revealed that these maps are plastic, meaning they can shift. They're subject to neuroplasticity, and there are specific rules that allow us to shift them. So here's the key experiment. The key experiment was done by a colleague of mine who's now retired, but whose work is absolutely fundamental in the field of neuroplasticity. Eric Knudsen, the Knudsen lab, and many of the Knudsen lab scientific offspring showed that if one is to wear prism glasses that shift the visual field, that eventually there'll be a shift in the representation of the auditory and motor maps, too. Now, what they initially did is they looked at young subjects, and what they did is they moved the visual world by making them wear prism glasses. So that, for instance, if my pen is out in front of me at five degrees off center, so just a little bit off center, if you're listening to this, this would be like, just a little bit to my right. But in these prism glasses, I actually see that pen way over far on my right. So it's actually here, but I see it over there because I'm wearing prisms on my eyes. What happens is, in the first day or so, you ask people or you ask animal subjects or whatever to reach for this object, and they reach to the wrong place because they're seeing it where it isn't. But what you find is that in young individuals, within a day or two, they start adjusting their motor behavior in exactly the right way so that they always reach to the correct location. So they hear a sound at one location, they see the object that ought to make that sound at a different location, and they somehow are able to adjust their motor behavior to reach to the correct location. It's incredible. And what it tells us is that these maps that are aligned to one another can move and shift. And it happens best in young individuals. If you do this in older individuals, in most cases, it takes a very long time for the maps to shift, and in some cases, they never shift. So this is a very experimental scenario, but it's an important one to understand because it really tamps down the fact that we have the capacity to create dramatic shifts in our representation of the outside world. So how can we get plasticity as adult that mimics the plasticity that we get when we are juveniles. Well, the Knudsen lab and other labs have looked at this, and it's really interesting. The signal that generates the plasticity is the making of errors. It's the reaches and failures that signal to these, to the nervous system that this is not working. And therefore the shifts start to take place. And this is so fundamentally important because I think most people understandably get frustrated. Like they're trying to learn a piece on the piano, and they don't know they can't do it, or they're trying to write a piece of code, or they're trying to access some sort of motor behavior, and they can't do it. And. And the frustration drives them crazy. And like, I can't do it. I can't do it. When they don't realize that the errors themselves are signaling to the brain and nervous system something's not working. And of course, the brain doesn't understand the words something isn't working. The brain doesn't even understand frustration as an emotional state. The brain understands the neurochemicals that are released, namely epinephrine and acetylcholine, but also, and we'll get into this, the molecule dopamine, when we start to approximate the correct behavior just a little bit, and we start getting it a little bit right. So what happens is when we make errors, the nervous system starts releasing neurotransmitters and neuromodulators that say, we better change something in the circuitry. And so errors are the basis for neuroplasticity and for learning. And I wish that this was more prominent out there. I guess this is why I'm saying it. And humans do not like this feeling of frustration and making errors. The few that do do exceedingly well in whatever pursuits they happen to be involved in. The ones that don't generally don't do well. They generally don't learn much. And if you think about it, why would your nervous system ever change? Why would it ever change unless there was something to be afraid of? Something that made us feel awful will signal that the nervous system needs to change or there's an error in our performance. So it turns out that the feedback of these errors, the reaching to the wrong location, starts to release a number of things. And now you've heard about them many times, but this would be epinephrine. It increases alertness, acetylcholine focus. Because if acetylcholine is released, it creates an opportunity to focus on the error margin, the distance between what it is that you're doing. And what it is that you would like to do. And then the nervous system starts to make changes almost immediately in order to try and get the behavior right. And when you start getting it even a little bit right, that third molecule comes online or is released, which is dopamine, which allows for the plastic changes to occur very fast. Now, this is what all happens very naturally in young brains. But in old brains, it tends to be pretty slow, except for in two conditions. So let me just pause and just say this. If you are uncomfortable making errors and you get frustrated easily, if you leverage that frustration toward drilling deeper into the endeavor, you are setting yourself up for a terrific set of plasticity mechanisms to engage. But if you take that frustration and you walk away from the endeavor, you are essentially setting up plasticity to rewire you according to what happens afterwards, which is generally feeling pretty miserable. So now you can kind of start to appreciate why it is that continuing to drill into a process to the point of frustration, but then staying with that process for a little bit longer. And I'll define exactly what I mean by a little bit is the most important thing for adult learning as well as childhood learning, but adult learning in particular. Now, the Knudsen lab did two very important sets of experiments. The first one, which showed that juveniles can make these massive shifts in their map representations. They get a lot of plasticity all at once. It happens very fast in the period of just a couple days. In adults, it tends to be very slow. And most individuals never actually accomplish the full map shift. They don't get the plasticity. Then what they did is they started making the increment of change smaller. So instead of shifting the world a huge amount by putting prisms that shifted the visual world all the way over to the right, they did this incrementally. So first they put on prisms that shifted it just a little bit, you know, and just like 7 degrees, I believe, was the exact number, and then it was 14 degrees, and then it was 28 degrees. And so what they found was that the adult nervous system can tolerate smaller and smaller errors over time, but that you can stack those errors so that you can get a lot of plasticity. Put simply, incremental learning as an adult is absolutely essential. You are not going to get massive shifts in your representations of the outside world. So how do you make small errors as opposed to big errors? Well, the key is smaller bouts of focused learning for smaller bits of information. It's a mistake to try and learn a lot of information in one learning bout as an adult. Now, there is one way to get a lot of plasticity all at once. As an adult. There is that kind of holy grail thing of getting massive plasticity, as you would when you were a young person, but as an adult. And the Knudsen lab revealed this by setting a very serious contingency on the learning. What they did was they had a situation where subjects had to find food that was displaced in their visual world, again by putting prisms. And they had to find the food, and the food made a noise. There was a noise set kind of the location of the food through an array of speakers. Basically, in order to eat at all, they needed plasticity. And then what happened was remarkable. What they observed is that the plasticity as an adult can be as dramatic, as robust, as it is in a young person or in a young animal subject, provided that there's a serious incentive for the plasticity to occur. And this is absolutely important to understand, which is that how badly we need or want the plasticity determines how fast that plasticity will arrive. This means that the importance of something, how important something is to us actually gates the rate of plasticity and the magnitude of plasticity. And this is why just passively going through most things, going through the motions, as we say, or just getting our reps in, quote, unquote, is not sufficient to get the nervous system to change. If we actually have to accomplish something in order to eat or in order to get our ration of income, we will reshape our nervous system very, very quickly. And so I think that the studies that Knudsen did showing that incremental learning can create a huge degree of plasticity as an adult, as well as when the contingency is very high, meaning we need to eat or we need to make an income, or we need to do something that's vitally important for us. That plasticity can happen in these enormous leaps, just like they can in adolescence and young adulthood. That points to the fact that it has to be a neurochemical system. There has to be an underlying mechanism. All the chemicals that we're about to talk about are released from drug stores, if you will, chemical stores that already reside in all of our brains. And the key is how to tap into those stores. And so we're going to next talk about what are the specific behaviors that liberate particular categories of chemicals that allow us to make the most of incremental learning and that set the stage for plasticity that is similar enough or mimics these high contingency states, like the need to get food or really create a sense of internal urgency, chemical urgency, if you will.
