[MUSIC] Okay so now, we're going to take a look at the hippocampus. We're going to start by looking at it. Where it is, generally. So remember we're looking at the base of the brain here. This is the front. This is the back. This is the, right and the left. And what, what, it looks a little weird. It does look a little weird because this piece here. This cerebellum has been removed. But what we're focused on right here is this, remember that this is remember that this is the Sylvian fissure and this is the temporal lobe. So this is the temporal lobe and you see on the inner part of the temporal lobe. Underneath, this bulge. This bulge right here. That bulge is called the uncus. And the uncus is a big chunk of brain. And the reason that we're going to talk about the uncus right now is because. Oftentimes, if there is an increase in, in pressure, due to a stroke or a tumor the pressure will press down on, on the hemisphere. And this uncus can slip down and start to press on the brain stem. It starts to press on the brain stem in a very specific spot. And, it presses on, you see? You see this? You see that? We should all thank this in our own bodies. This is the ocular motor nerve. This is the nerve that allows you to move your eyes vertically. It allows you to, to lift your eyelid voluntarily. It's also the, nerve that controls your lens and your pupil size. This nerve is very important for vision, for moving your eyes and for vision. And the uncus is just, when it presses down, when it, when there's too much pressure, it's going to press right onto that nerve. What's the first sign? Well the first sign is typically, that all of a sudden the person is confused because the, so much pressure has built up. And secondly their eyelid starts to droop. So all of a sudden droopy eyelid. Then you look in their eyes. And because of, for reason that we can go into in, in a weekly discussion. The eye actually deviates down and out. So this is a cardinal sign of a large increase in intracranial pressure. And it represents a medical emergency. Somebody with sudden onset droopy eyelid, which is called ptosis, P-T-O-S-I-S, and a down and out eye, confusion, unconsciousness. That is a sign of a of an acute episode, and that person needs medical attention right away. Okay. So let's try and figure out what's in here. Well, besides being a sign of intracranial pressure, what is in this part of the temporal lobe is in fact the hippocampus. The hippocampus is the part of the brain that allows us to make new declarative memories. So, what I'm going to do here, is I'm going to try to actually cut in and show you the hippocampus, show you what it looks like. So, I'm cutting in here. I'm going to cut a window. I'm going to try and get into the ventricle. And then follow that ventricle forward. Okay, so you see I just hit the ventricle. This Is an opening. You can maybe see the very smooth surface that is lining it. You also see stuff, well, like, did somebody leave crud in the brain. Well, in fact, this substance right here is something called choroid plexus. And choroid plexus is what makes cerebrospinal fluid. It pumps out the cerebrospinal fluid. It takes blood, it filters it into cerebrospinal fluid, or CSF. So we are in the ventricle, and we're going to follow that ventricle forward. [BLANK_AUDIO]. And you can see. You see that? You see this, this thing? Looks like a worm. Can you see that? It's leading us to the hippocampus. Okay, we're going to follow it forward. [BLANK_AUDIO]. Alright. So what do we have? We have a very nice, robust hippocampus. This is a little bit of stuff that we want to get off. You see this? This is all hippocampus, and then it ends in this nice foot-like structure that. Has made it reminiscent of a seahorse. So here's this hippocampus. It's a nice large hippocampus. I'm going to show you another hippocampus that I dissected previously so. Here we're looking at the hippocampus. And we can see the feet. You see this? Here it comes. This is oriented like that. This is the front. This is the left side. This is the back. So right here, this is the hippocampus. And you see those nice little paws? You see that? Okay. So that's the hippocampus. That's what we use to make declarative memories, both semantic memories and episodic memories. Okay? hippocampus. Now I want to share with you something that when I first saw it, it, it, it really, it really upset me. I don't, I don't know how upsetting it is for others. It's very upsetting for me. So this is a brain. From a individual who had Alzheimer's disease. And the first thing that you notice is that there's almost no cortex. This is the temp, this is the brain. Here's the front. Here's the back. Here's the top. This is the temporal lobe. And I don't know if you can see. But there's basically nothing there. It's, it's degenerated. It's lost. When I went here, I found, this is the hippocampus. Can you see that? I don't know if it's obvious to you that is much, much smaller than either of the other two hippocampus that we saw. It's barely a blip. Okay. So. This is the hippocampus. And this is the end of the hippocampus. It should be a robust foot-like structure. There's nothing there. Can you see that? So why did that upset me? Because when I look at that I realize that the people that lived with this individual and for this individual. As well. There was a lot of pain. This person was not able to make new memories. Painful for everybody involved. There's just no memory there. so, the this is one of the real tragedies. Is when the brain goes bad, in a situation like Alzheimer's. [MUSIC]
