That Neuroscience Guy - The Neuroscience behind Being Smart

Episode Date: January 24, 2024

What makes a genuis brain different from ours? Are they bigger? Do they have more brain cells? Did they just win the gene lottery? In today's episode of That Neuroscience Guy, we discuss what makes a smarter brain different. 

Hi, my name is Olaf 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. So let's just throw it out there. What makes us smart? Like, why are some people smarter than others? What makes us smart as humans? What is it about the brain that gives us our intelligence? On today's podcast, what makes us smart? Well, the first thing you might go to is the actual

physical size of the brain, like how big your brain actually is. And the human brain is quite large, but the brain of an African elephant is actually considerably bigger than ours. And even the dolphin brain edges us out by a little bit. So if we go back historically as well, we see that Neanderthals had bigger brains than us. So it's not the size of the brain that makes us smart. Otherwise, elephants and dolphins would be running the show and we would be coming in third. And for trivia purposes, there's a lot of debate about Albert Einstein's brain, but it's generally considered now that he had a slightly smaller brain than average in terms of size. So again, definitely not the size

of the brain that makes us smart. So then you might ask yourself, is it the number of neurons in the brain? And nope, it's not this as well. Humans have about 86 billion neurons in our brains on average, but most African elephants and short fin pilot whales have more neurons than we do. And if you go down the other route, just so you know, the average ant has about 250,000 neurons and the average roundworm only has about 30 neurons. So we have considerably more neurons in our brain than ants and roundworms, but elephants and certain types of whales have more neurons than we do. So you can't argue that our intelligence or our smartness, if you will, comes from the number of neurons in the brain.

And just to put that in perspective, you know, the Milky Way is pretty big as our galaxy, as galaxies go, but it has 250 billion stars. And there is us with 86 billion neurons in our brain. So it's quite a large number of neurons. But it is not why we're smart. There are animals out there, as I've mentioned already, that have larger brains, but they also have more neurons. brains, but they also have more neurons. And if we go back to Albert Einstein as an example, well, most estimates would say that the number of neurons in Albert Einstein's brain was about the same as the average human brain. But this is contentious, and there's a lot of analysis and reanalysis of Einstein's brain, and the debate is still raging. I'd say that the consensus among most researchers is that certain regions of Einstein's brain most likely had more neurons

than other regions. Well, what is it then? If it's not the size of our brains or the number of neurons in our brain, what makes us smart? Well, it's actually a couple of things. One, it's the number of neural synapses we have. So if you remember how this works, and we've talked about this a lot over the seasons, but when two neurons are connected in the brain, interneurons, they connect to what's called a synapse. And it's the axon of one neuron connecting to the dendrite of another neuron. And when an electrical signal called an action potential comes down the axon,

neurotransmitters released, it crosses the synapse. And when that neurotransmitter gets to the far side, it binds and that generates another small electrical signal. And that's how neural communication occurs. And to put this in more perspective, the average neuron in the human brain has about 7,000 synaptic connections with other neurons. So it's not one-to-one, which is sort of the picture that you see in a psychology 100 class.

These neurons are massively interconnected. And again, there's a lot of estimates here, but one of the more recent estimates that I think is probably close says that the number of synaptic connections we have in our brain is close to 600 trillion. So if you think 86 billion neurons, but 600 trillion interconnections. And what's interesting is that in young children, before synaptic pruning occurs, and we talked about that in a previous episode, that's basically when the brain is figuring out what neurons it actually needs

and it gets rid of a whole bunch. In young children, it's been estimated that number can reach as high as 1 quadrillion neurons, and then it gets trimmed back to 600 trillion, which are the ones we end up using. And you can see this quite clearly. If you go to Google Images and put in, you know, neural density brains with age, you'll see that in children, there are far more neurons that are there and far more interconnections, and these things get pruned away. Now, why are these connections important? Well, this is what changes with learning. When we learn something new, whether it's a sports skill or a new fact or a new face that you want to recognize, you form new neural connections. So you don't grow more neurons when you're learning. You don't increase the number of neurons.

Now, there's a little bit of debate that shows in some parts of the brain, the number of neurons probably does change with learning and in certain situations. But for the most part, most and pretty much all of human learning is forming new synaptic connections. So this is how the brain communicates. And one way I always try to visualize it is let's say that you have a face and a name that you want to put the two together. You meet someone new, their name is Fred, and you want to put the visual representation of Fred with that name. Now, both the visual representation and the name Fred would be represented by far more than a single neuron each. But for simplicity's sake, let's just assume that's true. So when you make that connection, you learn something new. Well, guess what? A new synapse is formed.

Now, another thing that could happen is that a synapse just becomes stronger with learning. So generally, when we talk about learning in the brain, we talk about more neurotransmitter being released. That's one way that we can learn. neurotransmitter being released. That's one way that we can learn. So through repetition or rehearsal or feedback, a neural connection is made stronger because more neurotransmitters being released, which means that little electrical signal on the postsynaptic neuron is bigger. You could have more receptors. So on the dendrite, on the postsynaptic neuron, you might get more sites for neurotransmitter to bind. And that again would lead to a stronger signal and make the neural connection stronger. And finally, the growth of new synapses. We've seen this. There's actually some really cool video footage online where people have actually done time-lapse photography of neural connections

growing. So that's another way that we can learn. So number one about things that make us smart is the number of neural synapses that we have. As humans, we've got this massive amount of neural synapses, which is why we are smart. There's also the relative size of the prefrontal cortex. There's a lot of estimates here as well, but on average, it's thought that the prefrontal cortex takes up about 30% of the human brain, which is ahead of all the other animals. So our massive prefrontal cortex is what makes us smart relative to other animals. And it probably isn't between humans. It's more why we can build cars and buildings and farm food, and your average dog can't do these things because they just don't have a very big prefrontal cortex. It is interesting to note that chimpanzees are

our closest competitor, and their prefrontal cortex takes up about 35% of their brain, and that is why they are sort of number two on the intelligence list if you rank animals around the planet. Now, just a little reminder there, because I've said prefrontal cortex, prefrontal cortex, prefrontal cortex, and that being bigger is what makes us smart. Well, the prefrontal cortex, if you remember from previous episodes, is executive function. It's the thing that allows us to set goals and make plans. It allows us to stop doing things that we shouldn't be doing. It allows us to switch between taxes. It allows us to switch between tasks and it controls working memory. So the prefrontal cortex is basically all of the

stuff that makes us human, our ability to make decisions and learn and do this long range or higher level thinking. Now, another thing that makes us smart, it's the third one I'm going to mention, are cortical folds. So if you go on Google Images and look at a picture of the brain, you'll see that the brain is heavily folded, all right? The cortex gets folded up, all right, and to make sure it fits within the brain. And basically the folds become gyri and the grooves become what are called sulci. And it's important to understand this because if you actually look at the average human brain,

it's not that big, like it fits inside your head. It's about 1,500 to 2,000 centimeters squared or 233 to 465 square inches. So if you unfold the brain and you pull out all of those folds, that is a part of what makes us smart because we have this massive surface area of cortex, which comes from the folding of the brain. And again, for just some brain trivia about intelligence, as we age, the folds basically open up. And if you do damage to your brain,

say you drink beer on a regular basis too much, you engage in other sorts of activities that aren't good for brain health, then those folds open up. And your homework, if you want, if you went on Google Images and put in cortical folds, Alzheimer's disease, you'll find any number of pictures of people's brains with Alzheimer's, where you can see that the folds are far more open than another person of the same age that doesn't have Alzheimer's disease. And I guess the last thing I should address is what makes some people smarter than other people? And the reality is it's two things. It is a bit of nature, just like we have different heights and weights due to genetics,

all right, different hair colors and so on and so forth, some people's brains are just built a little bit better than others, okay? They have more neurons, they have more interconnections, and their brain just literally, that allows them to think, you know, at a slightly higher level. But a lot of it's nurture, right? You know, a lot of intelligence and what makes us smart is the time you spend learning. So the time you put into studying and reading and having conversations and learning new material. And what that does, of course, as I mentioned earlier in the episode, that forms new connections and that is learning. And that's what makes some people smart. Anyway, there's a little bit on the neuroscience about

why we're smart, not brain size, take home message, not the number of neurons, but it's tied to the number of neural synapses, the relative size of the prefrontal cortex, and the way that our brain is folded, the cortical folds. Anyway, that's all I've got for today. Remember, check out thatneuroscienceguy.com. We are planning this season out and working our way through it. So send us some ideas, thatneuroscienceguy at gmail.com or of course on X or threads at thatneuroscienceguy.

Feel free to message me directly and we got some ideas coming in. And last but not least, of course, thank you so much for listening to the podcast. My name is Olive Craig Olson, and I'm that neuroscience guy. I'll see you soon for another neuroscience bite.