Hello everyone. Welcome to this tutorial on the anatomy of the internal capsule in the deep gray matter. Our principle core concept for this session is to simply again try to appreciate the complexity of the human brain. but to do so by guiding you through some principles that will help you understand that complexity. My learning objective for you today is that I want you to be able to describe and even to sketch the relations of the deep gray matter structures that we find within the core of the forebrain, with respect to the internal capsule. And this is an important white matter structure that runs right through the middle of each hemisphere. And I want you to appreciate the relationship of the deep gray matter to the internal capsule. As viewed in both the coronal and the axial plains of sections through the forebrain. What I want you to confront is the internal anatomy of the forebrain. What we find deep in the center of each hemisphere, and the chart here on this slide really provides you with a summary of what I want you to apprehend. So from embryological standpoint, the cerebral hemisphere consists of the telencphalon, which is the largest component of the cerebral hemispheres. And then just inferior and a bit caudal. We have the diencephalon. Now, what I want you to be able to do is to consider these various derivatives of the embryological telencephalon and diencephalon. And mainly, what we're going to focus on is one bit of white matter called the internal capsule. And the relationship then, of these gray matter structures relative to the different components of that internal capsule. Okay, so, yes we're going to see the cerebral cortex and, briefly the hippocampus and the amygdala in the temporal lobe. But really, our focus is going to be here, in the basal ganglia, and in the diencephalon, and in particular in the thalamus. So what I want you to be able to do is to recognize, how is the caudate nucleus, the putamen, the nucleus accumbens, and the globus pallidus positioned. Relative to the internal capsule. And then how does the thalamus, and the hypothalamus fit in. And essentially the answers to these questions will be either medial or lateral to the internal capsule. And then to complete the picture. We can consider the placement of some additional white matter structures. Such as our commissure of the fore brain. The corpus callosum and the anterior commissure. we'll see how the fornix fits in. And then I want you to appreciate how the ventricles that are associated with the fore brain. The lateral ventricle and the third ventricle. Our range relative to the deep grey matter in the internal capsule. Okay, well, let me show you what I'm talking about. If we look at the lateral view of the cerebral hemisphere, and if it were possible to look right through the cortex, as we are doing here in the illustration to the upper right. What we would see are a series of gray matter structures arranged around white matter, and the gray matter now are isolated for you on the left. And the colors that we see here are indicative of some of the major divisions of this deep gray matter. This purplish color shows us the basil ganglia. And the basil ganglia that can be seen from the lateral view includes the Caudate nucleus, the Putamen and the Nucleus accumbens. Now, you'll notice that they really don't look like their separate structures, but rather just a complex three-dimensional unitary structure. And indeed that's a very helpful way to think about the basal ganglia together these three structures are called the striatum because of the arrangement of cells in this general region of this structure between the putamen and the caudate divisions. Well I want you to understand, how is that striatum, or these divisions of the basal ganglia, arranged relative to the thalamus, and to the internal capsule? And you see the thalamus is positioned slightly posterior, but on the medial side Of the putamen, hopefully you get a sense of that. But there is this internal capsule that I've been referring to, and let me just sort of illustrate that for you here so you know how that fits in. The internal capsule is this massive system of white matter that runs between the cerebral cortex and everything that falls below the cerebral cortex. So that's going to include the thalamus, it's going to include the brain stem, and it's going to include the spinal cord. Now many of these axons as I have been illustrating here are heading in the descending direction. Some of them will actually go all the way down into the spinal cord. Other axons, namely those that are coming from the thalamus, are actually projecting back to the cerebral cortex. And so what we have in each hemisphere is this massive fan of white matter. That comes together in a compact bundle, and passes between parts of the basal ganglia, and the diencephalon. As this white matter courses from the forebrain down into the hind brain. Well, if we turn now to our enlarged view of the basal ganglia. This is exactly where we would see those axons. They would be slipping in this little cleft here between the body of the caudate nucleus, the thalamus, and the basal ganglia, the putamen, the nucleus accumbens. Now there's another component of the basal ganglia that we don't see here. That's also with the putamen on the lateral side of this internal capsule. And that structure is the globus pallidus. The globus pallidus would sit right about in this region here completely enveloped by the striadum. Now. If this seems a bit messy, I suppose it is. But, what I really want you to appreciate, is the way that these axons, of the internal capsule, provide such a useful landmark for us neuro anatomically. Because they help us understand where you would expect to find one of these important grey matter structures. And that's really what I hope for you to get out of this tutorial. Well, let's back up a slide. And I'll tell you exactly where you should expect to find these grey matter structures, relative to the internal capsule. Okay. So, again, our focus is primarily on the basal ganglia and the thalamus. What we would expect to find are two structures that are found on the medial side of the internal capsule. Those would be the thalumus and the caudate nucleus. On the later side of the internal capsule we would expect to find the putamen. And the globus pallidus. Now, what about the nucleus accumbens, you might ask? Where would we find that? Well the nucleus accumbens is really neither medial nor lateral. I would say it's actually inferior to the internal capsule, and you'll see what I mean when we look through sections of the brain. Well, let's do that now and I'd like to segue to a segment that I recorded in the brain anatomy lab and you'll see me directing your attention to these various components of the deep forebrain. So, take some time and take that in. Refer to the tutorial notes that I've given you. And then after we go to the lab, we'll conclude by looking at these sections in Silvius one last time. Okay? Well I'll see you shortly in the lab.