Okay, you guys, thank you for attending the class. So, finally, we meet with each other. Last time, I apologize for the delay. Now, my assignment for this segment of neurobiology or advance to neurobiology is about movement and a movement disorder. So, I would like to invite one student. Come up here please. We're going to show how movement is not something we should take for granted, and how intricate and how complicated it is. So, try that. All right, higher. Okay. All right. All right, so sit down please. So, in that movement, how many things are involved in this simple thing that we just take for granted? How many things are involved? What do you need to make this action? If we're going to understand movement, we need to understand from very bottom, all the way up. That is the beauty of neurobiology, right? Okay, let's see how many things we need our body system to do this. Let's try it. In today's class, by the way, we're going to be very, very interactive, okay. I've been teaching this class for almost 20 years, and last year, I was very lucky. I was voted by students to be one of the [FOREIGN], so they are going to announce that at the New Year's party. I'm very, very happy and indebted to the students. But in my teaching, every year, I want to get something new. So, this year, you are my [FOREIGN]. You are my guinea pig, so we're going to try something. Contracts. The other side has to coordinate, [FOREIGN], right? The other one has to relax, right there. Otherwise, if both of them are contracting, they'll be [SOUND], like this, okay. And you mentioned the eye, okay, which means it involves eye movement, right? The eye is following this one up and down, and remember, he actually accidentally hit the ceiling. So, this thing changed its trajectory. You were expecting it to be this and this, and suddenly, when it hits that, it comes down quicker, and then with a changed trajectory, right. So, eyes are constantly following it and they're making judgments, back and forth, back and forth. And with that, our brain is doing something to instruct our posture to change back and forth, right? We were expecting it to go this and this, and suddenly, [SOUND], it comes here, but we do that, no problem. It doesn't take a basketball player. It doesn't take a well-trained juggler, those people. It takes a normal person. Okay, now when the eyes are following that, we see that. What happened in our brain that we can make judgements? If we only see things, which means at a certain time point we see a position, the image goes into our retina, the retina goes to our optic nerve, the optic nerve goes to the brain, right? It will be always a reflection of reality, and only reflection of reality. But we get more than that, we can predict, right? So, because when it flies up, before it comes down, our brain is telling us it's going to go that way, so my hand and arm is already extending to that. We have a prediction. How do we know? How do we predict? That one has not happened yet, right? It's easy to reflect because you're here, you're here, okay. But the brain can predict in advance. It's going to fly this way and suddenly, when it hits that, it changed just very quickly. So, what's involved in our brain to judge, to predict which brain area is doing that? It's part of movement. Without that, we will never make that movement, right? Which brain region? Make a guess. If you don't know, just shout then make a guess. [FOREIGN] okay, very good. All right, all right. So, that's the movement I want to show you. To let everybody know, movement is something we take for granted without thinking. But it's really something we should not take for granted and we cannot take for granted. There are many, many conditions, disorders, diseases that impinging on some of the steps in this very complex thing called movement. I put an example of a great scientist, Steve Hawking. Does anybody know what Steve Hawking did? What did he do? Physicist, very good. What's his contribution? Black hole, okay. Black hole theory. That deals with one fundamental question in physics. And he also raised the possibility of what we called singularity. Time, space, light, and everything comes from one singularity, and from that point, everything comes. So, amazing guy. Steve Hawking suffers from a disease called ALS from pretty young age. And it's a miracle that he survived till today. Most of the ALS patients do not survive long. In the end, they cannot move their hands, and arms, and legs. Not only so, they cannot move their muscles in the costal. [FOREIGN] to the degree that basically they suffocate, all right. So, this is one of the typical movement disorders.