That Neuroscience Guy - Season 2 Finale- A Tour of the Brain

Episode Date: February 6, 2022

In previous episodes, we typically focus on certain brain areas as they relate to our everyday life. But how do all these brain areas fit together? For the season 2 finale of That Neuroscience Guy, we're giving you a tour of the human brain.

Hi, my name is Olof Kergolsen, 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 the last episode of Season 2 of That Neuroscience Guy. It's hard to believe this is our 42nd episode. Over the last 41 episodes, we've talked a lot about different parts of the human brain and how they impact and govern our day-to-day lives. However, I've come to realize that it's all been a bit piecemeal, leaping from one part of the brain to the other and telling bits and pieces of a story without framing it in a broader

context. It would almost be like me teaching geography and talking about all these cool countries all over the world, but never seeing where they actually are on the globe. So, class is in session. For our last episode of Season 2, I'm going to take you on a tour of the human brain, pointing out all of the key regions and their functions. And yes, you have homework. If you really want to learn this, get out Google Images and look up these brain regions as we discuss them. Press pause on the podcast and take a gander where they really are. And if you're

listening to this while you're out for a walk or a run or waiting in line at the bank, when you get home, take a look so you can see where these parts of the brain are. And you'll know this for yourself. So on that note, let's begin. If you look at the brain from the outside, you'll notice a bunch of things right away. You'll see the gyruses. These are the little bumps that are sticking up and the folds, which we call sulcuses or sulci. Now, you might wonder why the brain is all folded up in this manner with the gyruses and the sulcuses, and it's just not flat and smooth. Well, there's a reason for that. The cerebral cortex, the outermost layer of the brain, is where most of the high-level stuff occurs.

Thinking, memory, attention, perception, motor control, and a bunch of other things. And we need a lot of neurons to do all of this. So your brain is folded because it increases the surface area of the brain. Here's some trivia for you. The brain is about 1,500 to 2,000 centimeters square when it's unfolded. That's about the size to one to two pages of a newspaper. And obviously the human brain is a lot smaller than that. So to get all that tissue in, it has to be folded up, which is why we have gyruses and sulcuses. And if it was flat and

smooth, there'd be a lot less space for neurons and you wouldn't be able to do all the cool things that we can do as humans. Another trivia note, there's approximately 86 billion neurons in the brain, so we have to fold it all up so there's enough room for all the cool things to happen. Now, let's start with the outer layer of the brain, the cerebral cortex. It's divided into four main regions, the frontal cortex, the parietal cortex, the temporal cortex, and parietal cortex, the temporal cortex, and the occipital cortex. And let's start at the back with the occipital cortex. Essentially, the occipital cortex, which is on the posterior pole of the brain, so right at the

back of your head, it's your primary visual area. All visual information comes here. And this region is further subdivided. Area V1, for instance, is the very first area that receives input from the midbrain visual pathways, and it's responsible for detecting low-level visual features such as orientation and edges. As you move deeper into the occipital cortex, there are other visual areas, and these are responsible for extracting more complex features from a visual scene. And this is a key thing to remember about visual processing, that there's this build-up of visual information. Now, if we stick along the bottom of the brain, we have the left and right temporal cortices, one on each side. Now, the inferior or lower half of the temporal cortices

are devoted to visual processing as well. As visual information flows from the occipital cortex through the temporal cortices, we get a buildup of the complexity of the visual scene, which eventually ends up with object identification. There are areas like the fusiform face area, which is specialized solely for the detection of faces. But it's also been shown there are corresponding areas for the processing of objects and places. So when these areas are activated, you're at the final stages of visual identification. This flow of visual information is typically called the ventral or perceptual visual stream. Now the superior or top half of the temporal cortices do something as well. These regions are responsible for a range of other functions,

such as language and auditory processing, but the superior temporal cortices have also been implicated in mathematical processing and even in social cognition. Now, superior to the occipital and temporal cortices is the parietal cortex. The posterior parietal cortex is also a visual area. This is the back half of the parietal cortex, just above the ocietal cortex. The posterior parietal cortex is also a visual area. This is the back half of the parietal cortex, just above the occipital cortex. And it's this area, the posterior parietal cortex, is involved in the processing of spatial visual information, basically where things are in space. As with the temporal cortex, as visual information flows up

into the posterior parietal cortex, the visual representation gets more complex as we extract information to build our visual representation of the world. High-level visual areas in the parietal cortex include areas such as MT, which is an area that's responsible for the perception of motion. And if you remember our talk about this earlier in season one, you don't see motion, You interpret motion from a series of pictures. So here's your trivia if you've forgotten it. People with damage to MT have a rare condition called motion blindness. They literally can't see motion.

Now, the posterior parietal cortex does other things as well. It's been shown to play a role in the allocation of visual attention. We talked about that in our podcast on attention and also in motor control. And we talked about that on our podcast on grabbing an apple. The anterior portion of the parietal cortex does something very different. It is the primary somatosensory region of the brain. All of the sensory information coming from the muscles and joints is integrated here to create your physical representation of your body. So when someone touches your arm, that signal is sent up through your spinal cord and eventually arrives in the anterior parietal cortex in the somatosensory region.

Now last but not least of the cerebral cortices is the frontal cortex. The posterior half of the frontal cortex is almost entirely devoted to the control of movement. So we're talking about the frontal cortex, but the back half of it. So in other words, the back half of the frontal cortex, which is the portion that's just anterior to the parietal cortex. And if you want some neuroanatomy locations just anterior to the central sulcus. Now the anterior portion of the motor regions, so the front half of the back half if you will, are associated with movement planning, whereas the posterior regions of the frontal cortex, so the back half of the frontal cortex, and just anterior to the parietal cortex, well these regions are associated with movement production.

So indeed, if you stimulated the right region of the left primary motor cortex, you might cause the right biceps muscle to contract. Again, some more brain trivia. Never forget that the left side of the brain controls the right side of the body and vice versa. Now my favorite part of the brain, the anterior portion of the frontal cortex, which is also known as the prefrontal cortex. The prefrontal cortex has many sub-regions, such as the orbital frontal cortex, the ventral lateral prefrontal cortex, the dorsolateral prefrontal cortex, and many more. In broad terms, the prefrontal cortex is responsible for executive control. Planning, decision making, working memory, task switching, and all of those things that make us human. Now, here's some more

brain trivia. Humans don't have the biggest brains. Sperm whales, for instance, have considerably bigger brains and they weigh up to 20 pounds. But for humans, the prefrontal cortex is proportionally larger than any other mammal. Now, if you want to get a real feel for what the prefrontal cortex is proportionally larger than any other mammal. Now, if you want to get a real feel for what the prefrontal cortex does, think about how humans are different than other mammals. And then think about the mammals that are most similar to us. It might not surprise you to find out that monkeys and other simians have relatively large prefrontal cortices as well.

One more piece of homework. If you really want to get the prefrontal cortex, go on YouTube and look up Phineas Gage. That's P-H-I-N-E-A-S and the second half is Gage or his last name, G-A-G-E. We tell all of the first year psychology and neuroscience students about Phineas Gage, but if you look up his tail, it'll give you some further insight into what the prefrontal cortex actually does. Now another prominent structure that you might notice if you're looking at the outside of the brain is the cerebellum. It's the wrinkly ball-like structure that is below the acephalocortex and appears to be attached to the back of the brainstem. So what does the

cerebellum do? Now the cerebellum has traditionally been associated with motor control, particularly maintaining balance and coordinating movement. It's also been tied to vision and specifically control of eye movements. But more recently, the cerebellum has been heavily implicated in motor learning, which is how we learn movement skills. And it's also been associated with other functions. Researchers now believe that the cerebellum does play a role in thinking and processing language and even mood. And really cutting edge research ties the cerebellum to prediction. Our ability to predict what's going to happen given certain incoming information. Now we'll move briefly inside the

brain. There are too many structures here to highlight them all, so let's do a review of the main ones we have talked about over the past two seasons and add in a few new ones. Well, the thalamus. If you locate the thalamus, you'll understand what it does. The thalamus is basically right in the middle of the brain. It's in the midbrain region, and it's a relay station. One of the things we tell new neuroscience and medical students is that all sensory information goes through the thalamus as it passes into the brain, and basically all information. It's like a key junction. Incoming information passes through it, outgoing information passes through it. And by information, we mean

neural communication. Near the thalamus is the hypothalamus. If you think back to our episode on emotion, the hypothalamus basically controls a lot of the autonomic nervous system. So the parasympathetic and sympathetic nervous system, in other words, our glands, our sex drive, our sleep cycles, and all these kinds of things. So the hypothalamus is kind of like a governing body for all these low-level systems. And of course, we have our friends, the amygdala and the hippocampus. The amygdala is the emotional area of the brain. We've talked about it so much, I hate to bring it up, but hopefully by now you realize that if the amygdala is firing, you're experiencing emotions. And the hippocampus plays a crucial role in encoding memories, and especially our episodic and

somatic memories, our memories of trivia and facts and knowledge and our memories of what's happening in our lives. And it also plays a role in binding memories together. So when you're sleeping at night, it's the hippocampus and its activity that helps you remember things. And on a final note, you might remember that one of the reasons we remember emotional things is that the amygdala are attached to the front of the hippocampus. When the amygdala is firing, essentially it dials up the hippocampus, which is why we tend to

remember emotional events and forget things that are kind of blasé. Other midbrain structures that we've talked about include the basal ganglia. Now, I don't know if I've used that phrase before, but we've talked about the dorsal striatum, which is a structure that's involved in motor execution, and the ventral striatum, which is involved in learning. Now, the basal ganglia does include some other nuclei, but essentially these midbrain nuclei work together to govern things like movement and learning and other key cortical processes. Another structure that we've talked about, which is called the cortex but isn't on the outside, is the anterior cingulate cortex. The anterior cingulate cortex basically plays a key role in response selection. Given a given

piece of information, what should we do? And it also plays a key role in inhibiting our responses as well. So what else? So we've mentioned the corpus callosum in the past. If you remember, that's the structure that allows communication between the two hemispheres of the brain. And here's a couple of new ones. We've mentioned the pituitary gland, but just a reminder, the pituitary gland is essentially connected to the hypothalamus, and basically it's the master gland.

And what it does is it allows the secretion of hormones into the bloodstream. There's also the pineal gland. It's located near the third ventricle of the brain and basically it helps control your internal clock and your circadian rhythms. We haven't talked about it before but potentially a topic for season three. And last but not least there's the brainstem and the medulla and the pons. These three structures together are largely responsible for transmission of information in and out of the brain, but they also do some low-level processing. And as we leave the brainstem, that takes us out of the brain and to the end of our podcast today and the end of season two of That

Neuroscience Guy. I really hope you enjoyed that brief two of that neuroscience guy. I really hope you enjoyed that brief tour of the brain and I really hope you look up these cool brain regions and see what they do. We'll talk about them and so many more in season three. Thank you so much for listening. We're over 58,000 downloads in our first year and that's rapidly growing. We never expected it. I remember last year in February, at the end of the month, we had 245 downloads. And I remember thinking, is anyone going to listen to this podcast? And in January of 2022, which obviously just ended, we had over 13,000 downloads in one month. Thank you so, so much.

Now, Matt and I are going to take the rest of February off to plan Season 3 and get ready for it. And on that note, a big shout out to Matt. He's our producer and sound editor, and without him, that neuroscience guy wouldn't be a thing. And as we wrap up, just remember a few key things. Please remember to follow me on Twitter, that neuroscience guy, for the latest cool research from the Kregolson Lab and just other things I see. I tweet about it as much as I can. And don't forget about our YouTube channel. There's not much there right now, but we're planning on launching season three with over 80 videos. I'm porting over a bunch of content from some of my other channels and we'll create a few new videos as well. Our website is coming, thatneuroscienceguy.com. Right now it's an active link. It takes you to my personal page, but we will have a website up for season three because

we've got some cool ideas and other things we want to share with you. And finally, please email us your ideas for season three, thatneuroscienceguy at gmail.com. We really want to know what you want to know about the human brain and how it governs day to day life. My name is Olive Kregolson and I'm that neuroscience guy. Thank you so much for listening and see you in a few weeks for season I'm that neuroscience guy. Thank you so much for listening and see you in a few weeks for season three of that neuroscience guy. I'll be back and talk to you soon. Bye for now.