 So, can we start? Should we? Okay. In fact, all these videos are only there on the link because I did the pretty much the same thing in the previous batches also. So, let's first identify. Okay. So, this is the left hemisphere. I'm going to identify a few key structures on the super lateral surface. I'm going to identify everything on the medial surface and I won't be restricting my description only to the central cortex. I'm going to go into the brainstem also and the cerebellum also because we have covered all those things. So, let's start with what we did just today. The two most important salkai that we see, can you people see? Then what is the whole point? Do you want me to stand or something? The left hemisphere, as you can see, left hemisphere. Supralateral surface, supralateral, medial surface, orbital surface. We are clear up to this much. Let's take the two principal salkai which is present on the lateral surface. Can you see the first one here? This one. This is the central sulcus of Rolando. A few quick words about the central sulcus of Rolando. It starts from the supramedial margin. It goes up legally down and forward, but it does not meet the lateral fissure of Sylvius is an important point. It stops just short of the lateral fissure of Sylvius. So, therefore, the portion which is entirely anterior to the lateral central sulcus of Rolando is the frontal lobe. The portion which is posterior to the central sulcus of Rolando, most of it is the parietal lobe. Little bit of it is the occipital lobe, but there are no landmarks of the occipital lobe on the lateral surface. So, I'm going to show the occipital lobe landmarks on the medial surface. So, for the time being, frontal lobe, parietal lobe, are we good with this much? The portion which is below the lateral fissure of Sylvius is the temporal lobe. So, we are good with the four lobes, frontal, parietal, occipital, temporal. I'll tell you the landmarks for the occipital lobe on the medial surface because there are no identifying landmarks on the lateral surface. Okay. So, let's come to the medial surface now. I told you I'll show you the landmarks and you can see them all clearly here. Can you see this sulcus here? This is known as the P.O. sulcus. You've got to know this. Parietal occipital sulcus. It's very easy because it separates the parietal lobe on the medial surface from the occipital lobe on the lateral surface, on the medial surface. That's why it's called the P.O. sulcus. The parietal occipital sulcus starts from the medial margin and curves all the way down on the medial surface towards the spleenium of corpus callosum. It goes towards the spleenium of corpus callosum. And when it is going down, it is met by another sulcus which you will see just now. Here. This sulcus. This runs obliquely posteriorly. It's more visible here. This is called. Can you see? Can you see? That's why you're laughing. Can you see now? Can you see now? This is called the calcariant sulcus. These two sulci we have to know. So therefore this divides the medial surface into a portion above and a portion below. So parietal occipital sulcus and calcariant sulcus. These are not casual statements. They are important. The upper portion is called the cuneous gyrus. Cuneous means wedge. Cuneous gyrus of the occipital lobe. The lower portion is known as the lingual gyrus. Lingual means tongue. Wedge and tongue. We will stop at the occipital lobe there itself. We will not go any further now. Now let's come back again to the lateral surface. So we have identified the frontal lobe, parietal lobe, temporal lobe and occipital lobe. Now let's again go back to the frontal lobe. You see another sulcus just anterior to the central sulcus of Rolando. This one in actual life things are only as beautiful as we show them in our pictures. So you can see partly here, partly here. So which sulcus do you think this is? Which is parallel and in front? It's the pre-central sulcus. So the portion of the gyrus which is between these two is the primary motor. It's called the pre-central gyrus which contains the primary motor cortex. But we said the primary motor cortex is not only on the lateral surface, it also extends to the medial surface. Now I used a word on the medial surface. I called it the paracentral lobe. Now what is this paracentral lobe? It is when the central sulcus of Rolando dips in, it produces a slight bulge on the medial surface because it is dipping in. And that bulge on the medial surface which is not visible here is called the paracentral lobe. So the primary motor cortex extends from the lateral surface to the medial surface into the paracentral lobe. And the paracentral lobe is the leg area. Are we clear now? This is the face and the arm area. The face is represented here, the arm is represented here. The trunk and the body is represented here, the hip is here and the legs are dangling here. I hope most of you can see. Daniel, can you see? Then why don't you come here? Why don't you come? This place is vacant. Why don't you stand here? Why don't the little girls come here? I want everyone to benefit. Just remove this cover. Why can't the little ones come here and the big ones go behind? Anisha, why don't you come here? Pre-central gyrus primary motor cortex. And this is the paracentral lobe, the leg area. Just in front, this triangular area that you see here is the pre-motor cortex. This triangular area that you see here is the pre-motor cortex. Now let's continue. Can you see this gyrus sulcus here? This one. This is the superior and this is the inferior frontal sulcus. So therefore this whole thing is the superior frontal gyrus, the middle frontal gyrus and the inferior frontal gyrus. The frontal eye field is located where my index finger is situated. So this frontal eye field on the left hemisphere will control conjugate deviation of both the eyes to the right and vice versa. That's what we saw just now. Coming to the Broca's area. Can you see one, two and three ocular, triangular, orbital, ocular, triangular, orbital. Opercular and triangular, these two includes the Broca's area, motor speech area. And the rest of the frontal lobe is the PFC. Dorsolateral PFC, medial PFC. I'm going to tell you the parts on the middle side when I come to the middle side and orbit of frontal PFC. So these are the functional areas that you saw here. Let's come to the medial surface. Now we are going to identify everything which we have seen in other places. Corpus callosum. Do you want me to stand further back? Corpus callosum. Going from anterior to posterior. Corpus callosum is a thick sheet. You are seeing only the section here. It's a thick sheet which is extending from this hemisphere to that hemisphere. First of all, Corpus callosum does not extend the full length. It is not present in the anterior part. It is not present in the posterior part. It connects only the middle part. That is why if the two hemispheres were here and separated the hemisphere, I would have seen the Corpus callosum only in this portion. Okay. So this pointed inferior end of the Corpus callosum. What is the rostrum? This pointed inferior end of the Corpus callosum is the rostrum. This curved portion that you see here is the genu. The word genu literally in Latin means a bend. It is extrapolated to call the knee also, but actually it literally means a bend. So we have a genu of the Corpus callosum here. Then we have the body. And then we have the thick posterior portion here, which is the spleenium of the Corpus callosum. Okay. This portion that you see here, it has gone in the other half, will be the septum pellucidum. And below the septum pellucidum, there will be a white band which we shall see in another specimen. Some of those may have it. That is called the fornix. We will see the fornix in great detail in the chapter on hippocampus. It is concerned with your short-term memory to long-term memory, but we will not talk about it now. Now, if you trace the gyrus just superior to the Corpus callosum, this gyrus, it starts from below the rostrum, it starts from below the rostrum, goes all the way around and goes almost up to the spleenium. This is the cingulate gyrus, and we have come across the cingulate gyrus in plenty of context. Remember, when we have, this is the factory price here. Remember, so if there is increased intracranial pressure pushing from here, what will happen? The cingulate gyrus will tend to push to the opposite side and that is what we had called as the cingulate herniation. So this is the cingulate gyrus. Now, the cingulate gyrus, the anterior half of the cingulate gyrus belongs to medial PFs. The posterior half of cingulate gyrus belongs to the limbic system, but we will not talk about it. So cingulate gyrus has got frontal lobe functions and it has got limbic functions. Cingulate gyrus has got many other functions, we will see it later. So therefore, the sulcus which is demarcating the cingulate gyrus above this one, it curves up like this. This sulcus is called the cingulate sulcus. So the cingulate gyrus is between the cingulate sulcus and the corpus callosum. Next, this is the paracentral lobule. The portion anterior to that, this gyrus that you see here, this is the medial frontal gyrus, medial because it is on the medial side, to be distinguished from the middle frontal gyrus. Are we clear? Absolutely. This is M-I-D-D-L-E. I have had lots of problems. This is M-E-D-I-A-L. This is medial frontal gyrus. This is middle frontal gyrus. Middle frontal gyrus is the frontal ifean. Medial frontal gyrus contains the supplementary motor area and the rest of the medial frontal gyrus is the medial PFC. The medial PFC bilaterally controls the urinary sphincters. If you have a lesion of the bilateral medial PFC, you have urinary incontinence. You have uninhibited neurogenic bladder. That is why in one of the manifestations of frontal lobe science is uncontrolled mixturation, no voluntary control, no social inhibitions. They will be wet and they will be apathetic. They won't bother that they are wet. So, medial PFC bilateral lesion produces urinary incontinence. Coming to the other structures now, since we are already here, this structure that you see here because we are going to get sagittal MRIs. Remember yesterday I did mention this structure that you see here, this structure is the thalamus. In fact, when you take a sagittal section, it goes through the third ventricle. Why? Because the third ventricle is a midline structure. So, this sagittal section has gone through the third ventricle. So, what you are seeing here is the thalamus and what you are seeing here is actually the cavity of the third ventricle. Are we clear? So, the thalamus is this thing? This globular thing. This globular thing is the thalamus. This globular thing. And just right above that. Just right above that is the caudate nucleus. Right above that is the caudate nucleus. But I am not mentioning it now because we have separate dissections for the caudate nucleus, thalamus, hippocampus. We have got all. Right now I am restricting myself to the superficial parts. Yes, you want to ask something. So, there will be another thalamus on this side also. And in between the two thalamai we have the third ventricle. So, this thing has gone through the third ventricle. So, actually this is the ependymal lining of the third ventricle. Are we clear? Of course. You are going too far ahead. Hippocampus is in the medium side of the temporal lobe but we are not going to talk about it right now. That's why I said we have a separate dissection for it. So, the thalamus forms the floor for the third ventricle. Come again? Does it form the floor for the third ventricle? The thalamus forms the lateral wall of the third ventricle. About two-thirds. I am not going the floor because floor is formed by the hypothalamus. We are not bothered about that right now. Just look at this. Now to continue. The thalamus, if you were to continue down, everything is continuous. This portion where my index finger is located, now can somebody bring a probe from there please? Now is the time when I can use that. This is actually a brain knife. This is called a furkoff's brain knife. I don't need it now. I just need a probe. Can we see the pineal gland here or no? I will try to find a few. It's gone in the other house. Can I have a probe please? Just wait. Can you just show me one? This is called a furkoff's brain knife. It is made of tempered steel. You can cut from either end. You know, you can slash this way or this way. It's a very good knife. It is meant for cutting only the brain. It's very expensive. You can joystick it. Use the joystick. So now it's better. I can just throw it here and all of you can see it there. Okay. So this is the cavity of the lateral ventricle. My finger is going into the anterior horn. If I trace it posteriorly, it will go into the posterior horn. This is the body of the lateral ventricle. You can see it there clearly. If you look inside the body of the lateral ventricle, the roof is formed by the corpus callosum. Can you see that? The roof is formed by the corpus callosum. And if you look in the depths of the lateral ventricle, you can see this is the cordate nucleus. This is the cordate nucleus. Right now, I will not go further into the cordate nucleus because we have a separate dissection. Let me continue with where I was going. So this is the thalamus. If you were to trace the thalamus down from here to here is the tegmentum of the midbrain. So the thalamus and the hypothalamus continues into the tegmentum of the midbrain. And exactly here where my probe is pointing is the decastation of the superior cerebellar peduncles. I need you to look at that decastation of the superior cerebellar peduncles even in the section pictures which we have in the slides. This is where the decastation of superior cerebellar peduncles are located in the tegmentum of the midbrain. To continue, can you see the shallow groove here? This one. Can anybody guess what this shallow groove is? The aqueduct of sylvia. It connects the third ventricle through the aqueduct of sylvia to the fourth ventricle. See this triangular shape structure here. This is the fourth ventricle. Let me go step by step. The aqueduct of sylvia is located just one fourth of an inch, three fourths of an inch, sorry, three fourths of an inch long. It is located almost entirely in the midbrain only. So this aqueduct of sylvia divides the midbrain into an anterior portion which we just called as the mid-tegmentum. And the posterior portion which is behind the aqueduct of sylvia is the tectum or the quadrigeminal plate. And this tectum has got two swellings. Can you see one swelling here and another swelling here? So this is the superior colliculus and this is the inferior colliculus. The thunder and lightning reflects. Somebody was asking me the pineal gland. In this particular specimen the pineal gland has gone in the other half. But the pineal gland, sorry, the pineal gland will be located in this place where my I knew, I knew, I knew. I don't like that. The pineal gland will be located where the tip of my probe is. This is the location. Now just follow me. This projection that you see here, this is called the pulvinar of the thalamus. The pineal gland is located just above that. It will be hanging here. If it is, if it were not there, this will be the location of the pineal gland. Now you can see if this pineal gland enlarges, what will it do? It will compress on the superior colliculus. Yes? And that is how it produces perinod syndrome. It produces argile, robots and pupil. It produces convergent retraction, nystagmus. And it produces compression of the aqueduct of sylvia and can also produce hydrocephalus. This space that you see here, note this empty space. This empty space bounded by the quadrigeminal plate here, the cerebellum here and the spleenium of the corpus callosum here. This is called the quadrigeminal cistern. This is the one which contains CSF and this is the structure. This is the space where the pineal gland is located. It also contains the largest vein of the brain which we shall see later called the great cerebral vein of Galen. So this is the quadrigeminal cistern and this is where you see the calcification of the pineal gland. This is where you see the calcification. Now let us come to the fourth ventricle. We have finished with the midbrain. This was the lower limit of the midbrain if you remember. From here to here is the pons. From here to here is the pons. If you note the tegmentum of the midbrain continues as the tegmentum of the pons. Can you see? You can see the color coding is also more or less same, color coding, the brain. It is because it contains a similar set of fibers and you can see a portion anterior to that. Yes, yes, fine. You just keep telling me, no problems. This portion, can you see a light faint color here? What do you think that is? The scattered corpus corticospinal tracts. So this is the basilar part of the pons. Can you see this light color here? Those are the corticospinal tracts descending down and those same corticospinal tracts will descend down into the pyramids. Can you see the pyramid here? Yes. So that is the corticospinal tracts. So this is the basilar part of pons and the portion posterior to that is the tegmentum of the pons. Tegmentum of the pons continues as the tegmentum of the midbrain. So basilar part and this is where the basilar artery will be running here. And this is situated on the clivus, the sloping surface of the occipital bone. Now let's go behind. I said this is the lower limit of the pons. Remember, this is the lower limit. So this whole thing is forming the floor of the fourth ventricle. The whole thing is forming the floor of the fourth ventricle. The upper half of the floor is formed by the pons. The lower half of the floor is formed by the medulla. So this is the superior medullary vealum. Can you see this superior medullary vealum? It is a mixture of grey and white matter. And this is the inferior medullary vealum, which I told you does not contain any nervous tissue. It contains only pyromedre and arachnoid. Now I would like you to notice something very interesting which is here. Can you see this front like structure here? This fuzzy structure. This is the coroid plexus. This is the inferior medullary vealum. This is a branch of PIC, a pika, which is supplying the inferior medullary vealum. Take a look at the medulla has been partially cut off, but you can see the beginning of the pyramid here. Is it visible to everybody? This is the beginning of the pyramids. This is where you have the corticospinotrize descending down. Now let us come to the cerebellum. This section has gone through the vermes of the cerebellum. Can you see this branching tree like appearance? This is called arbor vitae. Just like any portion of the cerebral cortex, this has also got a portion which is outer that is called the cerebellar cortex. And the stem, so you can say that the leaves are the cerebellar cortex and the stem of the branches is the medulla. Cerebellar cortex contains the gray matter of the cerebellum, which we have seen contains three layers, the molecular layer, purkinje layer and granular layer. And the medulla contains the nuclei, festigial nucleus, interposed nucleus and dentate nucleus. Because this is the vermus, this will contain the festigial nucleus. Just lateral to the vermus if we were to take a section will contain the interposed. And in the lateral hemispheres, hemispheres will contain the dentate nucleus. So here this is the section. Okay, now let's come to the few, what other structures do I have to show you here? Can you see any of the cranial nerves from the side? Okay, let me show you something more because we have already mentioned it. I have opened up the lateral fissure of sylvia. Can you see this major artery here? This one. This one. This is the MCA. The MCA is coming out from the lateral fissure and it will split into two major branches. One branch will go up like this and supply the most of the lateral surface. The lower branch will come here and supply the rest of the lateral surface. That's why we said MCA is the artery of the lateral surface. It is coming out through the lateral fissure so you can see the branches of the MCA here. ACA is here. Can you see the cut end? This is the one which goes like this because while I am looking at this my hand is changing from this. Okay, this is the one which ACA will run like this all around and therefore it supplies the medial surface. So ACA is the artery for the medial surface. Incidentally, the PCA, the posterior cerebral artery will run round like this and come from here and it will supply the occipital lobe and the midbrain. The PCA. You cannot see the PCA here because it's almost gone in this specimen. It runs. This is the cerebral peduncle and you can see the branches of the PCA. Can anybody see? Oh, sorry, I went away. Okay, it's almost visible here. Yes, good. You can see the basilar arteries present here. Can you see this basilar? This is the PCA which is running around. It runs around the cerebral peduncle like this. It runs around the cerebral peduncle. This is the cerebral peduncle. The cerebral peduncle is the one which holds the midbrain to the cerebrum. That's why it's called the cerebral peduncle. It's like a pillar. Please do not confuse the cerebral peduncle with cerebellar peduncle. This is cerebral peduncle. This connects the midbrain to the brain, to the rest of the brain. This is the cerebral peduncle, this one where my probe is. The PCA runs around it and it supplies the occipital lobe as well as the midbrain. The midbrain is here. So this is what, so to come back to this specimen now, tomorrow we will take the, since we are going to start with the parietal lobe, I'm going to say a few words and then we will stop. As we said the posterior to the central sulcus is the parietal lobe. The parietal lobe also has got a similar sulcus like the pre-central sulcus. Can you see this one here? This one. Can we see this sulcus? What sulcus do you think this name will be? This will be the post-central sulcus. So again just like the pre-central sulcus, we have a post-central and we have a gyros in between. What will that gyros be called? Post-central gyros. And that is the primary sensory cortex. Just like this is the primary motor cortex. Remember all the, the tracks that we studied in our spinal cord, the spinal thalamic tract, the dorsal column, medial lemniscus, and didn't we say they all go to the primary sensory cortex? Broadband area 3-1-2. Now don't ask me why it is called 3-1-2 because I don't know. He named it 3-1-2 in that order. So motor cortex is 4, this is 3-1-2. This is the primary sensory cortex. This one. This is the primary sensory cortex. And you will see tomorrow that the homunculus on the sensory cortex is also exactly the same as the motor homunculus. So here is the motor homunculus. Here is the sensory homunculus. The same way. The face and arm will be here. The leg will be here. So the sensory homunculus matches the motor homunculus. On the primary cortex, we call it the motor homunculus. And on the sensory cortex, we call it the sensory homunculus. Same representation. Similarly, it goes to the medial side. Next, the rest of the parietal lobe, we will divide it again. And I will show it to you right now itself. Can you see this sulcus here? Yes, this sulcus. Where my thumb is? This sulcus. This is called, is it visible to everybody? This is called the intraparietal sulcus. I am going to mention it tomorrow. This intraparietal sulcus divides the rest of the parietal lobe into a portion above. Can you see this? A portion above and a portion below. Here, the portion above is called the superior parietal lobule SPL. And the portion below is called the IPL. Please remember these two terms because we will be using them very frequently and there will be lots of syndromes. Intraparietal sulcus divides this portion into superior parietal lobule and an inferior parietal lobule. Now we come to something very interesting. That is the lower limit of the parietal lobe. After that, there is nothing that starts the temporal lobe. So, we will not bother about that right now. Now, this superior parietal lobule is the only one which continues on the medial side. IPL is supplied by MCA. What about the SPL? It is partly supplied by the MCA and partly supplied by the ACA. That is one point I wanted to emphasize. Now, let us continue this SPL onto the medial surface. So, I am just turning to the medial surface. SPL continues onto the medial surface. This portion that you see here between this sulcus and this sulcus. This whole portion of the medial surface of the continuation of the SPL is called the pre-cuneous here. This whole portion is called the pre-cuneous. Why do you think it is called the pre-cuneous? Can anybody hazard a guess? Because it is in front of the cuneous gyrus which I told you was in the occipital lobe. Because you have to remember when we talk of the occipital lobe, maybe tomorrow or maybe day after tomorrow, we will talk of the cuneous gyrus and lingual gyrus. So, pre-cuneous belongs to the parietal lobe pp. Cuneous gyrus belongs to the occipital lobe. Pre-cuneous has got similar function as the superior parietal lobe. And we will see syndromes of lesion of this area. And they are very interesting. We will see syndromes of IPL below the parietal sulcus. They are also very interesting names. We will talk about them tomorrow. And finally to conclude just a few quick words that we have done. As we said, the temporal lobe is the portion which is below the lateral sulcus, lateral fissure of sylvias, this one. So, this whole thing is the temporal lobe. The temporal lobe also is divided into... Can you see a sulcus here? One sulcus here and there is another sulcus here. This is the superior temporal sulcus just like the superior frontal sulcus. And this is the inferior, some books call it the middle temporal sulcus. So, the temporal lobe also lateral surface is divided into a superior temporal gyrus, a middle temporal gyrus and inferior temporal gyrus. We will not bother about the middle and inferior now. Superior temporal gyrus contains our most important area that we need to know. Can anybody guess? The auditory area is located here. The auditory area. And we are going to talk about it. The primary auditory area is located here, where my probe has gone in. Just behind that will be the secondary auditory area. And just behind that extending from the temporal lobe onto the parietal lobe will be... Any guesses? The vernicase area. So, the vernicase area will be here. Again to repeat, this is the Broca's area. So, from here impulses will go to the Broca's area. The superior longitudinal fasciculus. It is not visible here because it is in the depth. It's in the white matter. So, we will see the primary auditory area, secondary auditory and vernicase area in the temporal lobe. These are the videos which I created last semester and I put them up just today in your respective slides. And these are the things which you will be seeing. So, tomorrow we will see the parietal and quickly we will finish the occipital and temporal.