Forebrain- Limbic System

Video Transcription

Hello, class. So just below the cerebral cortex, which is that outer layer of wrinkled materials that we recognize more readily within the brain, there are several other important structures that make up the forebrain, which is what we call all of these top and outermost structures of the brain. We refer to these internal sort of structures in the forebrain has the limbic system, which is an area of the brain involved in things like emotions, motivation, and memory formation. And this area acts as a sort of intermediary system to the cerebral cortex. It passes on a lot of the information and processes it in different ways. So we're going to took a look at four of these major structures in our lesson today.

So the first two structures that we'll talk about are easy ones to remember because they are related to each other. And in fact, their names give that away. They are the thalamus and hypothalamus.

Now, the thalamus is this smaller sort of football-shaped structure that's located at the center of the brain. And this area acts as a sort of conduit or conduction and switching center for all the sensory information that's being set up to the cerebral cortex. So if you recall, a lot of the areas of the different lobes of the brain are related to processing sensory information.

And this is sort of that in-between area, where it branches it out to the various areas that deal with those kinds of information. This is why this area of the brain is very important. And injury to the thalamus can lead to a loss of senses in general like deafness or blindness. The thalamus is also related to control of movement and sleep as well.

Now, secondly the hypothalamus, which is the even smaller, more circular gland that's located right in front of the thalamus, is involved in things like motivation and emotion within people. So one of the major duties of the hypothalamus is to regulate food, water, and sleep motivations. So damage to specific areas of the hypothalamus can result in different aspects of over or undereating, drinking, or sleeping. And this has been shown in rats as well as in humans.

So studies have been done in rats to find out which areas of the hypothalamus correspond with different activities, and damage to specific ones can lead to certain results. We have a very good knowledge of this important area of the brain. And remember, these are processes that are central to people, so that underscores how important this small organ really is. The hypothalamus is also involved in regulating the autonomic nervous system and controlling all of those kinds of regular body functions that keep us alive. So the things that we don't necessarily consciously deal with, like heartbeat, digestion, things like that, are helpfully regulated by the hypothalamus.

Now, after these two sort of smaller, more central parts of the limbic system, we also have what's called the amygdala, which is this small almond-shaped structure that's down here towards the bottom of the brain. And the amygdala is related to emotional responses within people. Now, it's especially related to emotions that have to do with survival, so things that go along with that fight-or-flight response, where it motivates us to survive in some kind of way. So these are things like fear, anger, or pleasure-seeking kinds of things.

So this is a basic structure that develops in other animals as well. It's something that a lot of other animals besides people also contain. But it's also still very powerful in people. So I don't want you to think that because it's basic it doesn't really serve a powerful function. That's not true.

It can lead to the creation of a lot of irrational fears or phobias. And if you have any kind of phobia you know that these are the kinds of things that are very difficult to shake. It's hard to get rid of a phobia. So you can see how intrinsic and powerful this organ can be to the formation of different kinds of thoughts and ideas.

And finally, we have the hippocampus. Now, hippocampus is this sort of crescent-shaped structure that appears on both sides of the brain. Remember, we have two different hemispheres. So we're talking about two of these crescent shapes that are moving-- that are inside of our brain. And these are related-- or this is related to the formation of memories.

Now, remember that as with all parts of the brain, the parts of the limbic system also work together in lots of ways. So the thalamus and the hypothalamus help to bring all of that sensory information to our higher levels of the brain. The amygdala attaches emotions and helps to create those quick-thinking sorts of responses. And they all act as conduits to relay that information up to the cerebral cortex.

So similarly, with all of that working in conjunction, the hippocampus takes all the sensory information and the emotions that these three other organs are using, and then attaches it to different kinds of events, and helps to create these strong long-lasting memories in our minds. So this is why a lot of sensory information can trigger memories in people. So, for example, the smell of smoke can automatically trigger a memory of camping trips when you were a child. And it's also why memories still have very strong emotions attached to them. So if you're remembering, say, a traumatic event from your childhood, you can still feel those same kinds of emotions because the hippocampus plays that central role in attaching those memories and creating meaning out of them so that they can last longer within our brains.