Learn more about the brain gyri and sulci or fissures. Get familiar with the anatomy and functions of the frontal lobe in this easy to understand video. Leslie has also included an interesting video about an individual with Broca’s aphasia, a defect in the Broca’s Motor Speech area resulting in speech problems.
Have fun learning!
Transcript of Today’s Episode
Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 065, I’m going to be talking about the anatomy and functions of the frontal lobe. But, before I talk about that, let’s talk about the folds in the cerebrum.
Now, when we’re talking about ‘gyri,’ we’re talking about the folds. You can see here in this brain, we have all these little folds that go all throughout the brain. Those are called ‘gyri.’ If you’re dealing with one of them, you’re not going to say gyri, but you’re going to say ‘gyrus.’
Then, we have the ‘sulci’ or the ‘fissures.’ Sometimes, we use these interchangeably, but these are the depressions in the brain that define the lobar boundaries. Here, we have the different lobes, and you can see we have all of these depressions, in other words, we have all of these grooves that are going throughout the different lobes of the brain. Those are called, ‘sulci,’ and in some cases, we call them, fissures.
So, with that understanding, let’s look at the frontal lobe in the brain. Now, the frontal lobe, we have two major boundaries that define the frontal lobe. Over here, we have the central sulcus. You can see that’s going through here. That is the posterior aspect (okay, so that’s towards the back). The posterior aspect of the frontal lobe, the boundary is the central sulcus.
Then, if we go inferiorly here, we have the lateral sulcus, or we can call it the Sylvian sulcus. That’s this boundary here on the inferior end of the frontal lobe. The central sulcus, posteriorly, and the Sylvian or lateral sulcus, inferiorly. And, this here would be the frontal lobe.
The first thing I want to talk about is this section here that’s called the precentral gyrus. Here, you can see in this case, it’s called the anterior central gyrus, but this is the precentral gyrus. The function of that region is it serves as the primary motor cortex. So, it’s basically getting motor signals from different parts of the brain, and it’s integrating it in this region. The precentral gyrus. This is where a lot of that motor function is integrated.
Just anterior to that, it’s not shown in this image, but I’m just going to kind of draw a section in here coming from the, from this part all the way. Maybe it’s not that right. It’s kind of, it’s not exact, but this is the pre-motor cortex, which makes sense. If this is the primary motor cortex, and this is, right before that, it’s the pre-motor cortex. Here, we have kind of an area that we call the ‘supplemental motor area.’ So, it’s the supplemental motor area. That plays a big role in initiating movements. You want to move, there’s an initiation that has to happen, and this has something to do with that process of initiating movements.
Now, as I said before, the boundaries aren’t necessarily definitely defined. I can’t see that it goes from right here to right there. But, in this area here, let’s show this area. I’ll just color it in a little bit. We have what’s called the ‘frontal eye fields.’ (Let me write that out—frontal eye fields). And, that is involved in the movement of the eyes, but a specific movement. When I look to the left and I look to the right, my eyes are moving horizontally. The frontal eye fields are involved in the horizontal movement of the eye.
Let’s move on. Then, we have, if we go anterior from that area, we have the superior frontal gyrus, the middle frontal gyrus, and the inferior frontal gyrus. So, superior, middle, and inferior frontal gyrus.
And, in the left hemisphere of the brain in the frontal lobe, we have an area that we call the Broca’s motor speech area. That has a big part to do with the motor components of speech. So, you’re speaking, I am speaking into this microphone right now, my mouth is moving in certain ways, and there are muscles that are controlling that, and this Broca’s motor speech area is very much involved in that process. Once again, it’s in the left hemisphere, not the right, and that deals with motor control of speech.
Now, if there’s damage to this area. If something happens, and that causes this area to be damaged, the result of that can be what we call, ‘Broca’s aphasia.’ When you have that condition, it causes a form of language impairment where you cannot speak well. It’s not that you can’t comprehend, but the motor control of that speech doesn’t function as well because the Broca’s motor speech area is damaged.
I have a little video here to show an example of that. So, let’s go ahead and take a look at that right now. (Video starts to play).
So, this is an example of Broca’s aphasia. You can see he had some problems speaking. Not necessarily in comprehension, but in just the motor control in forming the words and putting together long strings of the words to make complete sentences. That is an example of Broca’s aphasia.
If we look all the way into the anterior section, you’ll see that we have the prefrontal cortex and that plays a very important role in the process of intellectual functioning, and emotional responses, and so on. So, intellectual and emotional events that has a lot to do with what happens in the prefrontal cortex.
There’s another area that we cannot see in this picture, and in order to see it, we need to remove a section from here because it’s deeper in, it’s more medial. We’re going to do that now, and take a look at that. Here, you can see we have removed the part of the temporal lobe and part of the frontal lobe and then, here, there’s an area that we call the ‘insula.’ You can see it over here, and you can also see right here. This is the insular cortex. This picture over here is a coronal section of the brain. We just take a section of the brain right in this area, and you can see the insula right here.
Depending on what book you read, you might get different explanations as to the function of the insula, anything from taste, sensation, to emotions, to thoughts, pain sensations, visual sensations in terms of, you know, feeling hungry and thirsty. That’s attributed to that region. We’re not 100% clear on how this works, but we do have some suggestions as to its function.
The last thing I want to talk about is what we see right here. This structure is called the corpus callosum. That is responsible for connecting the two hemispheres, and you can see as the cortex goes medially, it borders in the inferior aspect with that corpus callosum. We can see it even clearer here. We can see the corpus callosum. You can see it starts here in the frontal cortex, and it goes back here. So, this is the corpus callosum. If we’re dealing with the frontal cortex, that does border with the corpus callosum inferiorly. That is shown very well right there.
That’s pretty much all I want to cover for this episode. As usual, you can visit the website at Interactive-Biology.com for more Biology videos. You could find transcripts of all the videos and a number of other resources to help make Biology fun.
This is Leslie Samuel. That’s it for now, and I’ll see you in the next one.