 And for that I have made a diagrammatic representation of the internal capsule on the right side. So to bring us up to speed this is the anterior limb of the internal capsule. This whole thing is the posterior limb of the internal capsule and the portion which is joining the two is the genome of the internal capsule and as we have already mentioned on the median side of the anterior limb we have the coordinate nucleus shown diagrammatically here. On the lateral side we have the lentiform nucleus which actually is indenting the internal capsule and giving it this V shape open laterally and on the posterior medial aspect of the posterior limb we have this thalamus here. Let us take a quick look at the posterior limb of the internal capsule because that is clinically more important. The posterior limb of the internal capsule we can divide the fibers into two broad groups as shown by this artificial color coding. This lateral bundle of fibers here this is the corticospinotract which I had shown earlier and I am going to show it again in another DTI image. This band of fibers that we see here this is the thalamocortical fibers which carry all the general sensations from the body to the somatosensory cortex of the parietal lobe. So let us take a look at the breakup of the fibers in the corticospinotract first because clinically this is very important. First this is the anterior portion. The fibers in the anterior part of the lateral portion of the posterior limb of the internal capsule are the corticospinotract fibers to the upper limb. Here the fibers are the corticospinotract fibers to the trunk and it also carries the corticorubril fibers that is from the cortex to the red nucleus of the midbrain. Going further posteriorly these are the fibers the corticospinotract fibers which go to the lower motor neurons of the lower limb and finally at the posterior most tip we have certain special type of fibers which come from the temporal lobe to the pontine nuclei they are part of the frontal pontine tract in this case they refer to as the temporal pontine fibers which are not bothered about them in detail anymore. So this whole segment is the corticospinotract fibers to the upper limb to the trunk to the lower limb remember that these are all fibers which are descending down and we are seeing the cut section in an axial view. Let's take a look at these fibers here this arrow represents the fact that the fibers descending the impulses are traveling up they are the thalamocortical fibers they go from all the sensory thalamic nuclei to the somatosensory cortex in the parietal lobe and they carry the general sensation from the body so this is the thalamocortical fibers carry now let's take a look at this portion here in circle in yellow this is the genome of the internal capsule now what do the genome carry the genome carries the corticoneuclear or the corticobulbar tracts and what are the corticoneuclear the corticobulbar tracts they are the counterpart of the corticospinotracts the only difference being they start from the face area of the primary motor cortex and they end in the motor nuclei of the cranial nerves three four five six seven nine ten eleven and twelve so these are the corticobulbar tracts and they supply the motor nuclei of the cranial nerves supplying the head and face so this is the genome one final word about this genome in the posterior limb the whole genome in the posterior limb are supplied by some very special arteries which are branches of the middle cerebral artery and these arteries are known as the lenticulostride arteries or the arteries of cerebral hemorrhage of sharko and these are the ones which are responsible for the vast majority of strokes involving the genome and the posterior limb of the internal capsule now let's take a look at the anterior limb of the internal capsule the anterior limb of the internal capsule the fibers are divided into for the sake of understanding into two groups the one's labelled green are the fibers which are coming from the frontal lobe to the pontine nuclei they are referred to as the frontopontine fibers or the frontopontine tracts now this is not just one fiber set of fibers they have a whole bundle of fibers and they are part of the corticopontine tracts just for the ease of understanding I have mentioned a few quick functions of these frontopontine fibers one of them is what is known as emotional smile the mimetic smile they carry fibers from the frontal lobe to the pontine nuclei to the seventh nerve motor nucleus smile emotional smile then we have the fibers for the horizontal conjugate gaze which goes from the frontal eye field to the paramedic pontine nucleus reticular formation nucleus in the pons for horizontal gaze then we have fibers for accommodation which do not go to the pons but they go to the nucleus in the midbrain and finally we have the fibers for multicontrol and coordinated mixturation which go from the mixturation center in the frontal lobe to the pontine mixturation center in the pons and therefore the M stands for mixturation so emotional smile horizontal gaze accommodation mixturation these are some of the just a few of the functions which have performed by these frontopontine tract fibers of course there are many more and there are many other functions this is just a few this central portion of the anterior limb the one marked in red here fibers are going up they are also thalamocortical fibers like these but there is a considerable difference between these thalamocortical fibers and these thalamocortical fibers while these thalamocortical fibers carry general sensation these thalamocortical fibers they do not go to the bridal lobe instead they go to the frontal lobe and one example of these thalamocortical fibers are that which is part of the MAPI circuit which goes from the anterior nucleus of the thalamus to the cingulate gyrus it is a part of the MAPI circuit so this is just one example of course there are many such thalamocortical fibers which are traveling in the anterior limb of the internal capsule so this is a diagrammatic representation of the internal capsule so in the anterior limb the genome and the posterior limb with the various types of fibers traveling which have been given color coding and the direction of travel of the impulses are also mentioned by arrows and finally the plus supply to the anterior limb of the internal capsule is the anterior central branches of the anterior cerebral artery so this is in a nutshell the various fiber tracks which are located in the internal capsule and this is again a diffusion tensor imaging and white matter tractography showing the disposition in a three dimensional view of the corticose spinal tract as we can see it is coming from the frontal lobe it is coming from the motor cortex and it is descending down and here it is the coronary radiator here it becomes the internal capsule and it descends further down and incidentally in this picture also we can see some fibers of another type of group of fibers which are referred to as the commissural fibers in this case it is the corpus callosum that is just by the way so this is the importance of the projection fibers which become the internal capsule and the very important component of these projection fibers namely the corticose spinal tract