Alright. So now, I'm going to feel like a little bit of a tour guide because over the next, actually, five lectures, I am going to take you on a tour of your brain. so our first stop will actually be the middle of the brain. And I, I think that's a good first stop because that's the most primitive brain structures. And so, let's start primitive and, and kind of go civilized, shall we? Off to primitive. Alright. So, Week 2 Lecture 3 Subcortical Regions of the Brain. What do I mean by subcortical? Well, first of all, we talked about all this wrinkled part on the outside of the brain. all of this is the cortex, the cortical regions and we're going to have a lot to say about cortical regions. But these all are kind of like the mushroom cap that sits upon a stem of a sort. And so, in the lecture today, we're going to talk about some of these regions. and I think it's, again, a good place to start because these are the very oldest parts of the brain. In fact, sometimes, this is referred to as the reptilian brain because literally if you look across species, even you know, all the way to, say, reptiles, you see these basic structures there in just about every species. so, it shouldn't be surprising then that the, the role these structures play are primarily ones involved with basic life support, really. so, for example, if we sort of work our way up the brainstem, it's like the spinal cord, we hit on the early part of the brainstem, something called the medulla. the medulla really takes care of things like our heart rate and our blood pressure and our respiration. So, just kind of synchronizing all those aspects to make sure, essentially, that enough oxygen and nutrients are flowing, flowing to our body. So, it's really taking control of, of that, you know, basic housekeeping function and keeping everything working well at that level. When we work up a little bit we get to the pons. This is kind of a fascinating area and we will have a lecture later all about sleep because sleep is a fascinating thing. And, and sleep is a case where that when we go to sleep, the neurochemicals in our brain really change quite dramatically. There's a whole shift. It really is an altered state of consciousness. And it's the pons that regulate all of that and regulate our general sleep wake cycles through the day. So, when you're feeling really tired, it's because the pons are kind of signalling parts of your brain that release chemicals that make you feel that way. So, that's the pons' job, really, is to work on our alertness and generally to every now and then make us desire sleep and then to regulate the changes in our brain that happen during sleep. So, sleep is a bit of a mystery. It's a hard thing to study scientifically but every animal does it. It must be important in some way, and clearly, you know, the part of our brain that regulates it, is part of this very primitive structure. As you move up, you get to what some people call the midbrain areas. And in those areas, you get a lot of control over things like sexual motivations, aggressive motivations, and again, you know, sex and aggression in, in the animal world especially well, in our world, too. face it now, aggression, we try to keep under wraps a little bit. But if we think about a more primitive society and, and primitive animals, let's say, the way sex typically works with animals, sex and aggression tend to be pretty linked. typically with animals, a female goes into a heat for a short period of time when they are ovulating. And then that period of time, the female will be receptive to almost any male. And just about every male will find a female in heat attractive. And so typically, a female in heat causes aggression in males. There becomes a competition over access to the females. and, of course, whoever wins or loses that competition, that's often critical for the hierarchical organization that those animals ultimately produce you know, they enter into. and so all of that, those sexual aggression behaviors are controlled by part of the mid brain up here so, you know, kind of fascinating. Think of, think of those basic things that keep the body alive and keep survival processes happening. That's all happening in the brainstem area really. And now, just to the right of the brainstem here, you see the cerebellum. In this slide, you see it along the bottom here. It's this little part that sticks out from our brain. Now, the cerebellum is actually very fascinating. and, and when we get up and talk about the cortical regions, I'll tell you that a lot of our motor activity is initiated by a strip of brain tissue that we'll call motor cortex. the cerebellum is kind of the next stop along the way. The cerebellum allows our motor behavior to be really graceful. I think very often, we don't fully appreciate how gracefully we do interact with the world, even things like going up stairs. and, and we quickly find the height of the stairs and we just barely clear that with our feet, or as we walk around corners. I don't know, if you've ever noticed this, but in Canada at least when Fall comes and we start wearing our heavier coats, I will often notice at that time that when I go around a corner, my coat is rubbing on the corners as I go across. So, obviously I have so little clearance between my body and the, and the corner, that once I add, you know, a centimeter or two of thickness, now I rub and, and touch that. So, the cerebellum really does orchestrate that really nice tight tuning of the body. And when there's problems in the cerebellum, you see a lot of jerky, uncoordinated kind of movement. So, very important for fluid motion, precise motion which, of course, also has survival value associated with it. But now, the parts that I really want to talk about today are parts that make up what we call the limbic system. there's, there's, there's a lot of fun in the limbic system and, and I'm going to be a little selective about what I talk about here. This tangle of nerve fibers, we've seen before, this is called the corpus callosum. This is the major connection between the two hemispheres of the brain. This is how most of the information goes back and forth through this corpus callosum. the last lecture in this series in, in this week, I will talk about patients who have had their corpus callosum severed and therefore, they essentially have two independent brains within their brain and there's some really fascinating cool data that comes out of those studies. So, I'm going to leave that a little bit until then. and in fact, the what I really want to focus on are two of these things, the amygdala and the hippocampus, because these are both very fascinating structures that are part of the limbic system. Let's start with the amygdala. the amygdala is, to some extent, our spider senses. that notion that if you're, if you're a Spiderman fan at all, there's that idea that every now and then, Spiderman can sense danger. There's danger around him somehow and he feels his spider senses tingling is what they will typically say. Well, you and I have a spider sense and it's the amygdala that underlies it all. So, essentially, any time we're in an environment and our brain perceives danger of any sort, it's the amygdala that is essentially our early warning system. It's, like, all the stimulae goes through the amygdala and the amygdala's job is to constantly be on the lookout for danger. And when it senses danger, well, guess what it does? It kicks in the sympathetic nervous system. Remember that switch? So, when the amygdala senses danger, then that switch gets flipped. Our heart beat starts speeding up, our breathing speeds up, we get anxious, we sweat, you know, all of that stuff happens. So, the amygdala is literally the switch that I talked about or it's at least the brain structure that flips that switch. and obviously a very critical role. If you remove the amygdala from an animal, it gets very easy going, very chilled out, which kind of sounds nice. However, if you remove the amygdala from a mouse, it's also chilled out when predators are around. That's not so good, right? That shows you the function of the amygdala, is that it warns us, hey, wake up, get ready, there's danger. You've got to be, you've got to be ready for it. Now it can also be a problem, of course, because if it triggers too easily, then we can feel like we're in danger when we're not. and that can give rise to things like panic attacks. So, panic attacks ultimately at their core are caused by the amygdala as well. Now, notice the amygdala is very close to the hippocampus. The hippocampus, that kind of means small sea horsey thing. It, it's this curvy C shapes structure that goes into one, one side of the brain and also into the other side of the brain. So, it's got this funky little shape to it. what it is critical for, we now know well, is laying down our conscious memories. If you have your hippocampus removed, then you will have trouble consciously remembering anything that happens to you after that, which is not to say you can't learn. You'll still be able to learn, but you will never consciously remember learning. So,if you've, if you've seen a movie like Momento, for example, or have heard of any amnesic where, you know, the story goes like this. You meet the amnesic, you talk to them, but if you leave the room and come back, they won't know who you are anymore. there are those sorts of amnesics, and they all have damage to their hippocampal region. So, the hippocampus really keeps our memories, our, our personal, what we're going to call episodic memories. it's the structure that seems to store those memories, and without it, it's, it's like a camera that won't take any pictures in a sense. Now, it's no coincidence that the amygdala and the hippocampus are so close. If you do find yourself in danger, it would be very handy, assuming you survive the danger, that you remember the conditions that were just before the danger appeared. Because if you do, that will allow you to potentially predict the danger if those conditions reappear. So really, this happens as a sort of circuit. Anytime the amygdala goes off and starts that whole sympathetic nervous system activity, it also stimulates the hippocampus, which seems to store information about what was happening just before the danger, thereby helping us to predict subsequent dangers. So again, think of this. This is all in the very primitive part of the brain. It's sophisticated to some extent. You know, its underlying conscious memory and escaping from danger but really it is about that short-term survival. So, we have, you know, some part of the brain doing that kind of housekeeping stuff but these parts of the brain are really trying to keep us alive when we're in danger and allowing us to avoid danger in the future. In a nutshell then, that's the kind of thing that these subcortical regions do. They, they work on keeping us alive allowing us to survive. I've got some other things. There's a nice anatomical tour of the hippocampus and the amygdala. Check that out. and there's a whole cool 3D brain tour. This will go beyond this lecture a little bit, but good to check out because we'll be, what we'll be talking about subsequently will follow along nicely. And remember what I told you about the amygdala and panic attacks. It's also relaxed to anxiety in general. that, that whole sympathetic nervous system activity, it's meant to be short-lived. the notion is it's supposed to help you escape some immediate danger. But what if you go to work and every day, you feel like you're going to get fired? So, every day, you feel like you're under threat. Well, your amygdala can be stimulated by that, and that can cause your sympathetic nervous system to be constantly engaged. You can feel constant anxiety, which is very poor for your health. So, this video will explore that a little bit. If you've ever had a panic attack or you feel anxious, check that out, that should be very informative for you. I've got some, some readings as well, a reading devoted to the primitive brain, the reptilian brain. and another one that focuses more on the hippocampus, because it's such a fascinating part of the brain and we'll be coming back to it, okay? So, that's the, the subcortical regions and from here, we're going to go, we're going to take the elevator, go up to the cortex. I'll see you up there.
