That Neuroscience Guy - The Brain Areas that Make Decisions

Episode Date: December 7, 2025

In today's episode of That Neuroscience Guy, we discuss the parts of your brain that contribute to decision-making.

My name is Olo Crig Olson, and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to the podcast. Okay, we're on the next step of human decision making. So in the last episode, I introduced the concept of System 1 and System 2. And we'll come back to that multiple times. And before that, we talked about value, the idea of a system. simple decision model, always choose the highest value. We introduced the explore, exploit dilemma,

and then I brought in this concept of system one and system two. So what I want to do with this episode is walk through the neuroanademy of this and at the same time tie it all together. I don't want you to think of these things in isolation. I really want you to bring it together so that when you think about human decision making, like you understand how it all. all fits together. You've got a framework for that, if you will. So it starts with the sensory system. Now, I'm going to focus primarily on vision for this, but of course the other senses could be integrated into this as well. And I'll point out that a couple of times, but we'll focus primarily on vision. So you're navigating the world, and you are at a food course.

I'm going to stick with food. Obviously, I'm obsessed with food. What can I say? So you're in a food court and you're looking around and that's your visual system. All right. So your primary visual cortex and we've got lots of episodes on vision. Your ventral stream for identification, your dorsal stream for, you know, figuring out where you are in space. This would obviously be largely a ventral stream activity because identification. And you're looking at the various food. choices in front of you. Now there's a flow of information there that goes you know through the inferior temporal cortex and this is you identifying that there is pizza and sushi. I'll stick with my my two classic examples here. So that's the visual scene integrated. Now obviously the olfactory system might be adding something to this. You might be able to smell the pizza for instance. and so on and so forth. Through all the sensory information is getting integrated in the brain.

Now, that, if you remember, our previous episode is the representation phase. All right. So what are the feasible actions? Now, we mentioned the idea of internal and external states. So what's the brain doing? Well, the brain's going, well, am I hungry? All right? Because you can walk through a food court and not eat.

All right? And if you are hungry, that's an internal. internal state that suggests maybe you should get food. And then the external state, of course, is just the century processing or what are my options available to me? And you come up with the idea of sushi or pizza. Now, the next phase is valuation. All right.

This is when you add value to the choices to you. Now, the human orbital frontal cortex, it's in the inferior aspect of the prefrontal region, has been heavily implicated in the role of valuation. There's all these studies. I told you about the car study with the three different cars already. And there's other studies that show that the orbital frontal cortex lights up

when you're assessing value. There are other systems that contribute to value. Your emotional system, our old friend, the amygdala, for instance, plays a role. But we're going to come back to the role of emotion decision-making in a future episode.

So let's say the orbital frontal cortex is adding value to these choices. Now, all of this information appears to be integrated into ventral medial prefrontal cortex. It's also taking information from the dorsal lateral prefrontal cortex. And the dorsal lateral prefrontal cortex is thought to be a gateway. All right. So it's a gateway into working memory. So your memory of pizza, your memory of sushi, your memory of these specific restaurants, that all gets integrated in the ventral medial prefrontal cortex. And as I said, there's, there's also input from the insula, all right, which is your emotional gateway, the strideum, which is a path from

the midbrain. Now, this is just going to be the sort of the full on, we'll start with system two, I guess. So this information is integrated and then you have to basically go through action selection. There's a lot of theories about where action selection occurs in the brain. I subscribe to one where it's the anterior cingulate cortex. So the anterior cingulate cortex is essentially taking in these values and it's working out which one is the highest value. It's assessing that for you. And it's the place where that kind of math happens.

All right. And the anterior cinglet cortex makes a selection. And then that information is essentially sent to the, motor system in a sense because you have to act on it so the the premotor regions get that information all right and they engage the motor system to walk you over to the pizza place because it's me and I always choose pizza so that's a system two decision and the reason it's system two is because you're assessing these values now in a true dual process account of this this would be the System 2 solution and you've engaged system 2.

One question that comes up a lot is why. And I hinted at this the last episode. And there's a lot of theories about this. But typically it's when System 1 fails in a classic model. So a System 1 solution to this problem, sensory information, I'm in the mall, I'm in the food court, internal state, external state, and you just go straight to pizza. There's no deliberation, right? You just, in this situation, you always choose pizza.

I have some friends that are like that. You know, there was a phase where my son would, when we went to the food court for lunch at the mall, it was always A&W. All right. There was no choice, no deliberation. He knew food court, mall, food court, A&W. Boom, boom, boom. System 1. All right.

For me, it was more of system 2 problem every time because I always wanted to assess, well, what food here is actually good and what would I like. So that's true dual process account. And like I said, I hinted at this in the last episode. So what is, if you believe more of a continuous model, then what happens is this process is very rapid, perhaps even automatic. And the prefrontal cortex is sitting there, sort of assessing, you know, do I need to get involved here? And why would the prefrontal cortex get involved?

Well, it would get involved because of uncertainty. and that's the most classic thing, which is you're uncertain about the values. Imagine the values are very similar for sushi and pizza, and the truth is, for me they are. It really depends on the day of the week and how I feel. And then the prefrontal cortex might throw in its weight to sort of do a proper assessment of value.

So the best way to think of system one system too is that there's an automatic process, just this very rapid selection. Sensory cortex goes through the lateral, inferior temporal cortex. That's you're adding in your visual information. You know, the emotional system might be throwing in some stuff. Like I said, we're going to come back to that. Orbital frontal cortex sort of is, you know, it adds value, but this choice is already made, all right? And that is akin to this idea of our simple decision model saying always, always exploit.

And then for whatever reason, the exploration part, you could think of as the gateway to system two. And again, I'll add some neuroanatomy here. Research from my own lab, like I've told you, suggests that it's the release of norapinephrine. And we actually did this experiment, a former PhD student of mine Cameron Hassel. It's called the Bart task. It's kind of a weird task. And when I see task, it's games. Because the way you do this in neuroscience is you have people play a game in the lab.

And then you basically look at, you know, what's going on in the brain. while they play the game. In the BART task, there's a balloon. And you basically just press the space bar on a computer to inflate the balloon. And every time you inflate the balloon, what happens is it gets bigger as you get more money, all right? And at some point you stop. You decide you're not going to inflate any further. And if that happens, you take the money. But in the BART task, people, what they do is they typically don't just push it once and think about it, push it once and think about it. Typically what they do is they push it like three or four times rapidly. Boom, boom, boom, boom.

And then they pause to assess, is that enough money? Now, when they're pushing it rapidly, we believe that system one. That's just go, go, go, go, go, pause. And on that pause, when you're deliberating, should I, you know, should I push again or should I not push again, that system two. that's the explore exploit dilemma. Do I go with the highest value option or do I choose another option? Now in this case, which one's higher value is hard to ascertain it?

It sort of flip-flops early on, presumably when you're pushing lots, then the higher value option is to go. When you decide to stop, that becomes the higher value option. And what Cam's research showed was that on these pauses, so when you explore, there's an increase, did this with EEG actually, we were indirectly measuring noropenephrine. But what happens is you get this increase in something called the P300. It's an event-related potential component. So that's an EEG response that's supposedly yoked to the release of norapinephrine. And what Cam found is that

when you when you're on these explore moments, there's more norapinephrine released in the brain. So there's another piece of the neuroanatomy of this, which is norapinephrine. and the locus serrilius, which is tied, again, it's controlled primarily by mid-brain structures, but in the case of exploration, the signal to release norepinephrine would come from the prefrontal cortex. All right. There are other players in this game.

You know, a lot of people talk about dopamine lots. They're really interested in, because they know dopamine and reward, and we've talked about it. Well, in this case, where dopamine fits into this, just so you know, is once you've made your choice and there's an outcome. So you get the pizza, all right.

And we've talked about prediction errors in the past. You can review those episodes. But if the pizza is better than expected, then there's an increase in dopamine. If the pizza is worse than expected, there's a decrease in dopamine. And what that's really doing, and maybe you can put it all together now,

is it's either increasing or reducing the value of the choice to choose pizza. All right. So that's where dopamine fits into this. So the goal of this episode was just to try it and tie it all together. So, you know, when we walk past this into the next phase of this, sort of journey through decision making, you're confident where you're at now. Okay, I'm going to go through it one time quickly as a sum up,

and then we'll call it a podcast. So sensory information, you're in an environment, you're faced with a choice. We'll stick with the, actually, I'll go to a new example. Let's say you're deciding to go to class or to skip class. All right. Classic university student problem. Sensory information, you're standing outside of the building where your class is. That's your state. Your internal state is how you feel about things. The external states where you are.

Your choices are to either skip class or not skip class. So that's the representation phase. That's your sensory system. Then you add in the values for these choices. There's a value coming from your emotional system. And like I said, we're going to do a whole, I'll do a whole podcast on emotional decision making. And there's values coming from the orbital frontal cortex, which is the more logical sort of thought process. Well, I have a midterm in a couple of days. I should go to class. That's the logical value. Now, we're assuming that we're in system two for this one. That means the ventral medial prefrontal cortex is assessing these values. All right. It's bringing it all together, that information is sent to the anterior cinglet cortex, and you make a choice.

Go to class, not go to class. The motor system either walks you into the building or it walks you away. System one decision would just be getting to the front of the building and just going in. All right, there's no deliberation. So system one is just boom, you walk into class, you go to class. All right. So sensory information, internal state, external state. Given this situation, there's only one choice.

The final piece I will add is why do system 2 get engaged? Uncertainty. All right. Information arrives. It makes you think, should I go to class or not? Should I not go to class? And that's when the prefrontal cortex kicks in. One more example, because I want to make sure you have this.

You're driving along and you are deciding, should I follow Google Maps? Because it's telling you a route that you wouldn't normally use. Or, you know, you. you are, you are, it aligns with what you normally do. So if Google Maps is aligned with what you would normally do, you would say you're in system one, because you just keep going. The decision is not to turn off at this turnoff that's coming up,

but I'll keep going because this is what I normally do, and Google Maps is reinforcing this. You get to the turnoff, and Google Maps is telling you to take it, but you know you normally go straight to get home. That's system two. All right, and the prefrontal cortex is engaged. All right, well, hopefully that helps tie it all together. so we're ready to dive deeper into decision making.

I've added in a bit of neuroanatomy so you can go online and get a map of the brain. And I'd encourage you to do that. I'd encourage you to try to map out these processes and where they are in the brain just to get a feel of the flow of information. All right. Don't forget the website, that neuroscience guy.com. There's links to Etsy, our store where we sell merch, Patreon, where you can support the podcast directly. You sign up a dollar a week, a dollar a month.

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