That Neuroscience Guy - The Neuroscience of Neuroplasticity

Episode Date: September 19, 2022

Sometimes, the area responsible for vision in a blind person's brain changes over time to complete different functions, like hearing. This extreme example of change in brain tissue is called Neuroplasticity, and it happens in all our brains at different levels.  In the season 4 premiere of That Neuroscience Guy, we discuss the neuroscience behind how our brain tissue changes over time and how that affects cognition. 

Hi, my name is Olof Kregolsen, and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to the podcast. And welcome to season four. We're back from some time away, but all of us got a much needed vacation, not just from the podcast, but from our day jobs. And we are excited for season four. Thank you for all the ideas that came in, and we're going to address them all and keep discussing the neuroscience of daily life. On that note,

the number one request we received during the off-season was from email or Twitter. And remember, you can follow me on Twitter at thatneurosciguy and send ideas, or you can email us at thatneuroscienceguy at gmail.com. And what that request was, was neuroplasticity, a definite buzzword in neuroscience these days. So for the first episode of season four, the neuroscience of neuroplasticity. Neuroplasticity is an interesting word. A lot of people throw it around whether it's in the workplace, in a school, or at home. I've heard teachers say, you know, you need to have more neuroplasticity.

And I've definitely been to workshops where people throw that word out there. But what does it actually mean and how does it actually work? On today's episode, the neuroscience of neuroplasticity. If we take people who were born blind or have been blind for some time and we examine their brains using neuroimaging, we see something quite interesting. Now, for those of us who have intact sight, the largest sensory area of the brain is the visual system. Indeed, the number of neurons dedicated to processing vision is larger than the total number of sensory neurons for the other four senses combined. Now, before we get into blindness and the example I just started, why is this? Why is vision so important? Well, quite simply, vision is a dominant sense that provides a ton of useful

information. So vision quite literally takes over our sensory brain. It dominates that part of the brain. But what about people who are blind? As I started to say, started the example, when we examine their brains using MRI or another imaging technique, we find that their visual sensory areas are reduced in size and that the brain regions devoted to the other four senses are greater in size. Now, these brain regions do not actually shrink. What actually happens is that some of the neurons in these regions get repurposed, if you will. So neurons in the primary visual cortex become used for other things, and neurons in the primary sensory cortex areas for the other senses expand into nearby territory. So they grow.

Just imagine an example of moving your yard a bit bigger every day is take over a bit more of your neighbor's yard and you use it for something that you want to use it for. Now, of course, I'm not suggesting you do that, even though I would really love to expand into my neighbor's backyard. Now, this gets even cooler. In a study down at the Catholic University of Levain, the researchers found that there was activity in the visual areas of blind people in response to language. So those regions were not firing because they're not being used because the people can't see.

They're actually being used for something else, in this case language. Another way to put this is that these visual neurons were being used for a different function. And this is what neuroplasticity means in the simplest sense. It is the ability of the brain to form new connections or change existing connections. Now, the most common form of neuroplasticity is learning. So for all of you that are listening, and for that matter, everyone else in the world, you've experienced neuroplasticity and you do on a daily basis because you learn. Now we've discussed learning in the past, but here's a quick review

framed in terms of neuroplasticity. Basically, we learn two ways. We learn by repetition and we learn through feedback. Repetition should be obvious. If you do something over and over enough times, you will eventually get better at it. Now, some of us learn more quickly and some of us learn more slowly through repetition, but eventually we all learn if we put in the hours. With feedback, the story is a bit more complex, but basically we can learn from external feedback. A coach or teacher telling us that we did something right or wrong, or even by seeing the outcome ourselves. Watching where a golf ball goes after we hit it is a form of external feedback. And even watching someone else do it. If you're watching someone else hit a golf ball,

that's a form of external feedback and our brains can learn from that. And like I said, we also process internal feedback. When texting or typing, you might have had the sensation where you know you did it wrong before you can even see the outcome. That's your brain processing the actual motor command and figuring out what you did wrong before you actually see it. Now, all of these things are neuroplasticity. Okay, okay, fine, learning is neuroplasticity. Neural connections are changing, but what does it actually mean? Well, here we go. Most of your brain is made up by what we call interneurons,

neurons connected to other neurons within the brain. If you'd like a computer analogy, the central processing unit, CPU, the big chip in the middle, is connected to the rest of the computer, of course, but most of the wiring in the CPU are wires connected to other wires within the CPU itself, a network of wires, if you will. Well, your brain is a network of neurons. if you will. Well, your brain is a network of neurons. When we learn, in other words, when neuroplasticity occurs, your brain is literally creating new connections between neurons in the brain, and you're rewiring the network. If you think of the example I used with blind people at the start, the neurons in the visual cortex are being reconnected to help process

language. Now, that's a pretty complex example, so let's hold that for a second. It started out with something more simple, just learning a new language. Now, I'm going to oversimplify this, but I'm sure you're going to get the idea. Let's say we're learning French, and we hear the word bonjour, and we are told that this means good day. Now all of this already exists in your brain. You heard the word bonjour even if you did not know what it means and you already know the meaning of the phrase good day. So what has to happen for you to learn again for neuroplasticity to occur, is that the neurons that represent the sounds

bonjour and the neurons that represent the meaning good day need to become connected. And guess what? Through repetition and feedback, they do just that. And if you want to think of brain regions and learning, there have been some really cool studies with piano players, as an example, where the neuroimaging shows that the regions of the brain representing the hand in the primary motor cortex are larger for people who play a lot of piano as opposed to people who do not play piano at all or only play a little bit of piano. Now, this is kind of like the language idea, but it's a little bit more complex. Basically, new neural connections are being made. Neurons near the hand areas of piano players

are getting connected to the hand area neurons of the piano players. So this is expanding into the surrounding turf idea all over again. And as a result, the area appears larger. But this is the formation of new connections, and that's neuroplasticity. And more importantly, this also means in the case of piano players, better manual dexterity, which obviously helps them play piano that much better. Now, why neurons in the visual cortex in blind people start firing to language is a bit more complex to explain. And if I'm being honest, neuroscientists have a lot of theories as to why, but realistically don't know. We just know that it occurs and we're starting to map it out and starting to think

about why that is. But it's neuroplasticity all the same. Neurons changing their purpose. And it's not just with blindness. Basically any major change in function will most likely result in neuroplasticity people have had a limb amputated have activity in the parts of the brains associated with the motor regions of the limb and the sensory regions of the limb even though they're not being used and there's so many other examples here, it's almost impossible to highlight them all. But one of the major theories out there is that neurons want to fire. So inactive neurons are basically, if they don't get used, it's not like they die off, but they're seeking a purpose, if you will. And the brain's kind of greedy, so it's going to see those neurons not doing anything and say, well, hey, let's use them to do this. All right. Now,

that's a high level theory, but that's the working idea is that neurons that aren't being used for anything get repurposed. And that's what's underlying the neuroplasticity in the blind people or the piano players that I've talked to you about. But I'm still failing you. I've not really explained how it really works at the lowest level. So here we go. And this is a bit of a review from our episode in season one on learning, but I'll cover it all the same. Let's just consider two neurons, neuron A and neuron B. Learning or neuroplasticity in the simplest sense is the strengthening of the connection between these two neurons. And please bear in mind that what I'm actually talking about is thousands or millions of neurons, but I'm taking it down to two just

to work through the example. So how does the connection between neuron A and neuron B get strengthened? Well, in essence, a stronger connection means one of two things. It means that either more neurotransmitter is getting released, or there are more receptors for neurotransmitter. So when neuron A fires, an electrical signal called an action potential is being sent down the axon of the neuron, and when it gets to the end, it causes a release of neurotransmitter, effectively a chemical that's being used to transfer the signal. So the electrical signal causes the release of the neurotransmitter. Now that neurotransmitter floats across the synapse and it binds. It binds to what's called a receptor. And when it does, it generates a small electrical signal called an excitatory or inhibitory

postsynaptic potential. That's neural communication. For a stronger connection, for a stronger connection, more neurotransmitters getting released, or there are more receptors to bind onto that neurotransmitter. And that's learning. You've made the connection between neuron A and neuron B stronger. Why? Because if neuron A fires and it releases a lot of neurotransmitter, or there are more receptors, neuron B is going to fire. And if there's not enough of either, it's not going to, and therefore there's no connection. So that's one form of neuroplasticity, this increase in neurotransmitter being released, or this increase in receptors. But what about the formation of new connections? Well, this is another form of neuroplasticity, and sort of the third form of

change, if you will. And we call this sprouting. And that's literally what happens. The axon terminal of a neuron splits and reaches out and connects to another neuron, literally forming a new connection. Now, to be clear, new neurons are not being formed. That doesn't happen very often in the adult brain, but a new neural connection is being formed and that can happen throughout the lifespan. So what is neuroplasticity? It's an increase in the amount of neurotransmitter being released. It's an increase in the amount of receptors that are postsynaptic neuron, or it's a growth of a new connection. So if you think of the language example, you hear the word bonjour and you want to associate it with the meaning good day, well,

you could do this simply by connecting those neurons and having more neurotransmitter being released or having more postsynaptic connections or both. And if you think of the blind example, well, new connections are being formed. Language neurons from the language parts of the brain are becoming connected to visual neurons, and those neurons therefore start firing and become a part of the processing of language. Now, if you want a more in-depth explanation of this, you can re-listen to the episode on season one about learning, because I get into long-term potentiation and long-term depression and even lower level of this mechanism of change. Now, finally, how can we facilitate neuroplasticity? Well, I'm sadly afraid that this is becoming a podcast theme. And for the frequent listeners, you can already guess what I'm going to say. You know, in fact, this is quiz time.

You can improve your sleep quality, you can eat a healthier diet, and you can exercise more because all of these things facilitate neuroplasticity. Now, again, we've touched on all that before in a previous episode, so I'm not going to go into it further here. So there you go, our first episode of season four in the neuroscience of neuroplasticity. Now we haven't finished planning season four out fully yet. So if you have ideas, follow me on Twitter and DM me at that neuroscience guy or email us at that neuroscience guy at gmail.com. Our Etsy store is still up. Of course, thank you to all of the people that have purchased

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It really does. And remember all that money goes to supporting graduate students in my lab at the university of Victoria. None of it goes to me. Thank you so much for listening and don't forget to subscribe to the podcast. I'm so excited to be kicking off season four of TNG and I'll see you on Wednesday for another neuroscience bite. My name is Olaf Kregolsen and I'm that neuroscience guy. Thank you so much for listening.