 The last and finish of the last remaining functional areas of the oxfiddle lobe The oxfiddle lobe is unique in the sense That there are no well-defined external landmarks on the lateral surface So therefore we start describing the oxfiddle lobe from the media service So let's take a look at the picture of the brain as we have left it off in the media service Just to bring up to speed This was the area which we had highlighted as the pre-cunious which we had said was the media continuation of the superior brighter lobe Let's put a few sulkai and gyri in place on the media surface Take a good look at this sulcus here This sulcus starts right from below the spleenium of the corpus callosum and goes all the way up This is called the parieto-oxfiddle sulcus Why is it called the parieto-oxfiddle? Because it separates the parietal lobe anteriorly from the occipital lobe posteriorly That's why it is called the P.O. sulcus, the parieto-oxfiddle sulcus Let's bisect this parieto-oxfiddle sulcus with yet another curved sulcus That is known as the calcarine sulcus When we bisect the parieto-oxfiddle lobe by this calcarine sulcus Now we can see that we have divided the media surface of the occipital lobe into two parts A superior portion and an inferior portion The superior portion or more precisely it is referred to as the superior bank And the inferior is referred to as the inferior bank of the occipital lobe They have been given specific names The superior bank because it is shaped like a wedge It is called the cuneus Just to bring you up to speed, let's take a step back If you remember the portion just anterior to the cuneus we had given it a name We had called it as the precuneus Now we can understand why it is called the precuneus because it is anterior to the cuneus So this superior bank is referred to as the cuneus gyros And the inferior bank below the calcarine sulcus because it is shaped like a town It is called the lingual gyros These two are the most important areas which are considered vision And they are seen best on the media surface However we shall also see them on the lateral surface in the subsequent slides Now, having put this sulcus and gyros in place Let's put the functional areas in their locations You will see that each of the gyros, superior bank and inferior bank That is the cuneus gyros and lingual gyros They have got the primary and the secondary visual areas Symmetrically arranged above and below the calcarine sulcus The first here and here, these two lines are the primary visual areas B1 Broadband area 17 Which is responsible for just visual perception only The next two parallel lines above and below are Area 80 and 19, the secondary visual cortex Which are also referred to as B2 and B3 These are for higher order visual perception and for visual recognition While we are on the media surface, I need to show you a few other extra points also Let me put two other sulci and a few other parallel lines in place on the media surface But mind you, they will not be restricted only to the occipital lobe They will be spilling over partly also to the medial surface of the temporal lobe And here we are We have put another sulcus here This sulcus is referred to as the collateral sulcus The collateral sulcus starts from under the lingual gyros And as it goes forward, it changes its name and becomes known as the reinal sulcus Rhino means nose It is not part of our present discussion but I am just telling you so that we can understand it The collateral sulcus continues and becomes a reinal sulcus And there is another sulcus later to the collateral sulcus Which is known as the occipitotemporal sulcus With these two sulcus in place, let's demarcate the gyri and make a quick mention of the function Because these areas are integrative in nature They are partly related to vision and partly related to other things This portion which is medial to the collateral sulcus is known as the parahepocampal gyros Though it is seen on the medial surface, it is actually present deep inside the medial surface We will not talk about it any further because it is part of the limbic system And it is also associated with smell That's why this portion of the sulcus is referred to as reinal sulcus We shall not go into the details right now Let's focus on this gyros here and this gyros here If you remember, this was the occipitotemporal sulcus So therefore the gyros which is medial to that is known as the medial occipitotemporal gyros And the gyros which is lateral to that is known as the lateral occipitotemporal gyros Let's focus on the medial occipitotemporal gyros As you can see from the term, it is called occipitotemporal gyros That's the reason I put it up here That means it extends from the occipital region and goes all the way to the temporal region But this is seen only on the inferior surface This area has got again a very unique function This area is concerned with facial recognition The ability to recognize a person by his or her face is unique This occipitotemporal gyros is also referred to as the fusiform gyros And this has been the subject of a lot of research And if there is a bilateral lesion of this occipitotemporal gyros, bilateral lesion The person has the ability to recognize faces And that is called prosopagnosia In this unique condition called prosopagnosia The patient cannot recognize a person by his or her face However, when the person speaks just by hearing the voice The person recognizes the other person So that's the unique condition that is called prosopagnosia So you can see that this is the area of higher order visual processing It's a very high order visual processing And there are lots of studies going on So these are some of the important areas that we see Not only of the temporal lobe, occipital lobe, but also extending it to the temporal lobe Which we have highlighted Now let's come to the lateral portion, lateral surface and see As we have already mentioned, occipital lobe There are no clear landmarks on the lateral surface But occipital lobe does exist on the lateral surface So in order for us to show you the location of the lateral surface, occipital lobe What we have done is we have drawn an imaginary line And because it's an imaginary line, it has not been highlighted in blue But it's been highlighted in black This imaginary line extends from where the parietal occipital sulcus Where the parietal occipital sulcus ended And it went down to a notch on the inferior border Known as the pre-oxcipital notch This imaginary line extends from that area And this is an imaginary line There is no landmark on the lateral surface This portion which is posterior to that is the occipital lobe Now let's put the other functional areas in the lateral surface of the occipital lobe And see where they go First take a look at this inset picture This is the lateral surface We can see here that the lateral surface also has got The visual areas 1, 2 and 3 Primary visual area 17 Secondary visual area 18 and 19 So not only are they present on the medial surface But they also extend on the lateral surface Incidentally, before I proceed any further The extreme tip of the occipital lobe is called the occipital pole And this area is responsible for macular vision This occupies one third of the entire visual cortex And it serves the macular guy As we go a little anterior in the lateral surface We see another large area Though it has been shown in the occipital lobe Again, let me remind you that it is not really restricted to the occipital lobe It extends into the parietal lobe And it also extends into the temporal lobe This area is known as the visual association area V4 is known as the parbocelular lobe system What does this do? This is a very high order area It is responsible for again facial recognition That means V4 does send communication to the occipital temporal virus V4 is also responsible for color recognition And V4 is also a parbocelular lobe system V4 is also responsible for pattern recognition So therefore, if there is a lesion of V4 or parbocelular lobe system The person loses these three functions The person becomes prosopagnosia Acromatopsia cannot recognize color And cannot perceive the patterns of objects And then we have another area It is also part of the visual association area called D5 The magnocelular stripe system What does this do? This has got intimate connections with area 7 That is why I have arrows here This area is concerned with motion, depth and spatial perception Therefore, it helps us to determine the speed of objects The distance of objects and how far they are from us These areas, as I said earlier They are not restricted only to the parietal lobe Or to the occipital lobe They have got extensive connections with area 39 And I told you a little while back, 39 is a very important area So you can see here So they extend to the 39, extend to area 7 Therefore, this communication of the occipital lobe With the parietal lobe is referred as a parietal occipital junction Likewise, this area has also got connections with the temporal lobe And this is called the occipital temporal connection Parietal occipital lesion bilaterally produces what is known as Balance syndrome Enable you to fixate your eyes at a specified point And also we have mentioned occipital temporal lesion produces Prosopagnosia So these are the final, and finally there is one more functional area Again, which is not shown here But it extends to a wide variety, wide area in this region That is known as the occipital eye field Which is responsible for involuntary psychotic movements of the eyes