Source: image brain: public domain; http://en.wikipedia.org/wiki/File:Human_brain_NIH.jpg; image brain lobes: public domain; http://commons.wikimedia.org/wiki/File:Brain-anatomy.jpg
Hello, class. So in today's lesson, we're going to get a little bit more in depth into the actual structure of the brain itself, talk about what the parts of it actually are. And you can see a quick picture of what a brain might look like. This isn't exactly to scale. This is a little bit of an artistic interpretation on my part, but you can get a good sense.
So this outer layer with all these different kinds of wrinkles, these little folds and these bumps that are all put together of gray and sometimes some white matter, is what we call the cerebral cortex, this outer layer of itself. And it's probably the most recognizable part of the brain itself. Now, this cerebral cortex area that's outside of the brain is responsible for most of the recognizable aspects of a person's mind, things like personality, thought, language, the storage of memory, movement, and our senses. All these things are related to the cerebral cortex.
Now, humans have a very developed cerebral cortex compared to a lot of other animals, which is why we're considered to be more intelligent and aware of those animals. But it's important to note that humans don't have the largest brains out of every animal. That would be the whale, which is a much bigger animal, and so as a result, it has a much bigger brain. And also it isn't the most wrinkled or defined cerebral cortex, which would go to the dolphin, which actually does have a bit more of a larger, more developed cerebral cortex. So this isn't necessarily the only reason why humans are considered to be so much more intelligent, but it's definitely one of the reasons.
Now, if we were to take a look at the brain from a different point of view, instead of looking at it from the side like this, if we were to look at it instead from the top, we would see that the brain, or the cerebral cortex specifically, is divided into two halves. We call this the left hemisphere and the right hemisphere, with a little space in between, which we call the medial longitudinal fissure. That isn't something necessarily to memorize. But just remember, there is a space in between.
And the two brains-- sides of the brain-- are connected by this bundle of neurons in between that I have here in red. This is what we call the corpus callosum, that connecting area of the two hemispheres. Now, this is important that we have two different hemispheres, because it provides a sort of backup for any kind of brain function. There's always two of each structure. So if one of them has a problem, the other one can help out.
But each side of the brain also has certain specific functions that it does, and those are generally relegated just to that side of the brain. And this is what we call lateralization of function. And this is generally true for most people, but some people, 5% of people, might have these switched over. So it's important to remember that.
But generally, when we talk about lateralization of function, we talk about people being either left brained or right brained, because each of them, first of all, controls a different side of the body. So your left brain that we talk about actually controls the opposite side of your body. So my left brain sends signals to the right side of my body to move. Whereas the right side of my brain controls the left side of my body. So a lot of times if you see, say, a stroke victim who's having trouble with one side of their body, say, their right arm and movement, it's because they have damage to the left side of their brain. So it's important to remember that opposite side.
Each side also controls different types of thinking. And to find this out, actually there were studies that were done with something called split-brain patients. And these are people that have their corpus callosum, that connecting part in the middle of their brain, severed.
So it was cut, mainly because of epilepsy. This is a procedure that's done to help out with major epileptic seizures, people that have them often. And they found that when you cut that corpus callosum, generally people act the same. And that's because both eyes, when they're looking around stuff, can see what's happening around them so both sides of their brain will also see and react in their normal ways. However, if you show each eye a different image, if you were to separate it so that only one side of the head could-- or one side of the eyes could see something, you'll find that because that corpus callosum is severed, that eye is only responding to one part of the brain.
So, for example, when the left hemisphere, or the right eye, was shown an object, the person could say what that object was. However, if the right hemisphere of the brain or, in other words, the left eye, was shown an image, they couldn't actually say what that image was. But if they were asked to draw whatever came to their mind, they would draw the image that they saw.
So you can see the left side of the brain-- oops, sorry, the left side of the brain is related to logic, language, coordination. It's the analytical side of the brain. That's what a left-brained person would be. Whereas the right side of the brain is related to spatial, visual, or emotional sorts of things. This is the artistic or holistic side of the brain.
So going back to our side view of the brain, we see that each hemisphere, the left and the right, is divided further into four different lobes. And each of these lobes is a specific or generally defined area of the cerebral cortex that's related to different kinds of functions of the brain. And we'll go into more of the details of each of these sections a bit more in other lessons.
But generally, what you might want to remember is that the frontal lobe is related to higher-level thinking tasks. So these are things like a sense of self and also self-awareness and personality as well as movements. So this is an area of the brain that's very highly developed in humans, and it leads to a lot of those specifically human things that we talk about.
Outside of that, we also have the parietal lobe, which is the area that's related to the sensory sorts of information, things like touch or temperature. We also have the temporal lobe, which is related to hearing and language. And finally, we have the occipital lobe in the back here, and the occipital lobe is related to sight. So each part of the brain is divided first into two hemispheres, right and left, and then into four lobes-- frontal, parietal, temporal, and occipital.