That Neuroscience Guy - Emotion

Episode Date: May 30, 2021

Why does your heart race when you hear horror movie music? How does being sad lead to craving ice cream? In today's episode, I discuss the neuroscience of emotion. 

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. Have you ever felt happy or sad? Well, of course you have. We all experience emotion. And that's what we're going to talk about today. The neuroscience of emotion. At a fundamental level, you could argue that our emotions stem from very primitive learned behaviors. For instance, the fight, flee, feed, and reproduction responses.

behaviors. For instance, the fight, flee, feed, and reproduction responses. These are innate to all of us, and we're hardwired to respond to these scenarios. It's built right into us. But how does that happen? What does our brain do when we experience emotional events? Today, we're going to pull that apart and look at the different brain structures that play a role in our emotional response and talk a bit about what they do. When neuroscientists talk about emotion, one of the terms that will come up right away is the limbic system. The limbic system is not a single brain region, it's actually comprised of multiple brain regions. And these brain regions are the parts of the brain that are thought to play a critical role in emotion. The limbic system is comprised of four main parts, the thalamus, the hypothalamus, the amygdala, and the hippocampus.

Funnily enough, there's a lot of debate as to what structures make up the limbic system. If you open one textbook, it will identify some structures, and if you open another textbook, it would identify different structures as being part of the limbic system. However, neuroscientists generally agree that those four main regions, the thalamus, the hypothalamus, the amygdala, and the hippocampus, are all the main components of the limbic system. Let's talk about what they do. First, we'll talk about the thalamus and the hypothalamus. We'll talk about them together because while they are different neural structures, they work together to form our emotional response. At a high level, you can think of the thalamus and the hypothalamus as controlling our body's

response. And I'll explain that in terms of the responses that are controlled by these two brain structures. For instance, the hypothalamus controls the pituitary gland, and the pituitary gland plays a crucial role in controlling the thyroid gland and your blood pressure. So if you have an emotional response and your blood pressure seems to go up have an emotional response and your blood pressure seems to go up, it's because the pituitary gland controlled by the hypothalamus is firing. The hypothalamus also plays a crucial role in controlling the autonomic nervous system, specifically the sympathetic and parasympathetic nervous system. So what is the sympathetic and parasympathetic nervous system because we haven't

talked about them before? Well, essentially the sympathetic and the parasympathetic nervous system work together. For instance, the sympathetic nervous system will dilate the pupils and the parasympathetic system will constrict the pupils. The sympathetic system will inhibit salvation and the parasympathetic system will stimulate salivation. I'll give you one more example. The sympathetic system will accelerate your heart, and the parasympathetic system will inhibit your heart. I think you can see that all of these things, changes in pupil size, changes in salivation, and changes in your heart's response, changes in salivation and changes in your heart's response are a part of your emotional response to events in the world. The hypothalamus and the thalamus also play a crucial role in regulating

the body's temperature, which again is something we've all experienced when we have an emotional response. It plays a role in fluid balance. For instance, that sensation of needing water or the fact that you feel parched. They play a role in eating. So the fact that you might feel hungry or you might not feel like eating at all. I know I've had an emotional response where it made me feel like the last thing I wanted was food. And I think we've all had an emotional response where we wanted ice cream. The thalamus and hypothalamus also help in the sleep-wake cycle. For instance, if you feel really tired because you're in an emotional state, this is tied to the thalamus and the hypothalamus.

The thalamus and the hypothalamus also play a role in our sexual responses, which of course are tied to emotion. And critically, the thalamus and hypothalamus bring in sensory information and pass it on to other parts of the limbic system, the amygdala and the hippocampus. So of course, this is crucial for our emotional response because we need all of these brain regions to be working together. The key idea in understanding the role of the thalamus and the hypothalamus in emotion is that these brain structures control our physiological response. So if you're emotional and you get the

sweats or your heart starts beating faster, it's the thalamus and the hypothalamus that control your emotion. It's the thalamus and hypothalamus that control your emotion at this level. Now, another key brain region in our emotional response is the amygdala, and we've talked about it before, so I won't spend too much time on it, but I'll give you a quick refresher. You actually have two amygdala, one on the left side, one on the right side, both attached to the front of the hippocampus, and the amygdala is a higher level emotional response. I'll give you some examples with research studies. Early research in studying the role of the amygdala in emotion looked at face processing. Participants in studies were put in an fMRI scanner so their brain's response could be measured, and they were shown a series of faces. And what these studies show is that the emotional response

in the amygdala is larger for fearful faces or happy faces than it is for neutral faces. This gave neuroscientists a key insight that the amygdala is obviously sensitive to emotion at some level. And this is combined across an array of studies that have shown that the amygdala is obviously sensitive to emotion at some level. And this is combined across an array of studies that have shown that the amygdala responds when an emotional stimulus is presented. So if you think about this, what it means in the real world, when you're having an emotional response to something, part of that response is the amygdala firing. I'll give you another example from research.

It's been shown quite clearly now that when people are in a sleep-deprived state, they have an emotional response. And if you look at the neuroscience of this, researchers measuring activity in the amygdala have shown that there's increased activity in the amygdala when you're sleep-deprived. So one of the reasons you're emotional when you're tired is because the amygdala when you're sleep deprived. So one of the reasons you're emotional when you're tired is because the amygdala is firing a little bit more than it does when you're rested. The amygdala plays another crucial role in terms of its emotional response, which is it helps regulate memory formation. If you think back, you'll probably find that you tend to remember emotional events quite well, and you tend to remember events that were quite boring or had no emotional response not as well.

The reason for that is that when the amygdala fires, it dials up the activity in the hippocampus and other brain regions associated with memory formation. So the reason that you remember emotional events in your life is the amygdala, when it's having its emotional response, is also telling the hippocampus, which as we've discussed before, plays a crucial role in memory formation, to work a little bit harder. In other words, the amygdala is pushing play on the record button in your memory system. Now the last part of the limbic system that I mentioned was the hippocampus. Well, the role of the hippocampus in emotion is memory. Emotional responses are quite fast, but they can also be prolonged. And when you see something, part of that emotional response

is memory, remembering that that sound or that image is scary. Let me give you an example of the role of the hippocampus and memory in the emotional response. We've all learned that certain sounds are scary. For instance, and please forgive my poor attempt at reproducing this, the sound of a scary movie. this, the sound of a scary movie. Well, that sound you've learned means that someone's going to leap out with a knife or the doll is going to come alive and start attacking people. And you've learned that through repeated exposure. You've seen scary situations and they've been associated with that sound. So that sound triggers the emotional response. And it's a form of memory. And think about an experiment you could try. Imagine taking a young child and training them

that that sound means that care bears will appear and start dancing around. Well, the young person won't process that sound as having a negative emotional content or a scary content, and they'll process it with something happy is about to happen. And that's a response that will be there. And you could imagine you could also condition someone to ignore that sound. Every time they hear it, nothing happens. And they'll turn it off and not have an emotional response. So let's try and tie this all together imagine an emotional event happens you see something that upsets you for instance well the first thing that happens is that information is processed by our sensory systems but very quickly the thalamus and the hypothalamus and the amygdala get involved

and the thalamus and the hypothalamus and the amygdala get involved. And the thalamus and the hypothalamus are regulating those physiological responses. They're making your heart beat a bit faster. They're making your mouth feel dry. The amygdala is kicking in very quickly as well. And it's firing because it's going, well, this is an emotional thing. I'm going to respond to that. It's working concurrently with your hippocampus where you're remembering what the emotional response is in a sense. You're remembering if you've seen this thing before or you haven't. If you have and it's associated with emotional response, then that's the hippocampus telling this system, well, hey, this is emotional. We need to respond. So all of these brain

regions work together to create an emotional response. That's a brief overview of the neuroscience of emotion. My name is Olof Kregolsen, and I'm That Neuroscience Guy. You can check me out on YouTube. I have a channel, That Neuroscience Guy. And you can follow me on Twitter, at That Neurosci Guy. It's a great place to ask questions for the Ask a Neuroscientist episodes. And last of all, we host this on my website, www.olivkrigolson.com.

Thanks for listening, and have a great day.