So in this video, we're going to be talking about cerebral white matter. We've been spending a lot of time in the gray matter. So let's kinda go subcortical and see what that white matter is up to. Cerebral white matter is responsible for communication between cerebral areas as well as some lower CNS centers, including the spinal cord. White matter gets classified into 3 groups basically depending on the direction in which it flows. The direction that those fibers or tracts are moving, and you'll see that in just one second.
We're going to go through each of those groups. We'll kinda see what they look like and talk about what they do. Association fibers, which we have here in green for you, are restricted to just one hemisphere. They're either in the left or right hemispheres, and these connect cortical gyri. Now, you can see here we have our association fibers in green and you can see how they just kind of loop between the gyri of one hemisphere and connect them and allow them to associate with each other to talk, right, and to communicate.
Now, in blue here, we have commissural fibers. Commissural fibers run left to right and they connect the left and right hemispheres, and the largest set of these fibers is the corpus callosum, which we have pictured here for you in blue. These are the commissural fibers of the corpus callosum. That's a very important structure as it allows our left and right hemispheres to communicate, which allows for coordinated activity between the two of them.
And then here in red, we have our projection fibers. Projection fibers are a bit similar to association fibers in a way because they operate or they connect the cortex within just one hemisphere. And these also, as you can see, these kind of run all the way down into the spinal cord. So these also connect the brain and the spinal cord, so very important to allow our brain to communicate with the rest of our body.
Projection fibers form two structures. The first one down here is the internal capsules. This is kind of like a dense, very tightly compact area of these fibers. And then right superior to that, we have the corona radiata, which you can see this area right here is the corona radiata. You can see how the fibers kind of fan out or radiate outwards. Corona radiata actually means "radiating crown," which is kind of what these fibers look like here. Just to fill this out, these are our projection fibers in red.
Alright. So we have our association fibers, which allow communication between the cortical gyri of one hemisphere. We have our commissural fibers, which allow the left and right hemispheres to communicate, and we have our projection fibers that allow the spinal cord to communicate with the brain. Right, so that is our white matter in a nutshell, and I will see you guys in our next video to finally finish up the cerebrum. So I'll see you there.