[MUSIC] Okay, let's talk about Parkinson's. Now, Parkinson's results when the dopamine-containing neurons in the substantia nigra. For those of you keeping score at home pars compacta of the substantia nigra so when these dopamine neurons die now as it turns out these dopamine neurons in particular contain a pigment called neuro-melanin and that pigment makes them black. So let's come over here to a section. And here we've taken a section about like this, through the human brain. Here's the, the telencephalon, this is all, this is telencephalon and diencephalon. And here we have right here, this is brain stem, this is actually midbrain. And this area right here, that, this dark area, that's, those are the substantia nigra cells that produce dopamine. Now if more than 90%. Of these cells die a person will start to get, show the symptoms of Parkinson's. 80% of them that are dead, 85% of them are dead, the person is not going to be symptomatic. But once about 90% of them die. Person becomes symptomatic with Parkinson's. Okay. So we can tell right off the bat that this individual did not die with Parkinson's. It has plenty of, of this black, which is a sign of the nermellon of the dopamine cells. So how does dopamine, what does dopamine do for movement? Well it does two basic different things. One is, that it provides essentially motor oil. And this is a, a tonic function. Which means that it is always happening. So the, the, the engine of movement. The engine of human movement is not going to happen without oil. Without motor oil. And that motor oil is dopamine. You don't have the dopamine. You're not going to move. And in fact if you make animals that don't have dopamine. Animals that lack the ability to make dopamine, they die within days. They never feed, they don't, they just don't move around, and they die. So, if this is the amount of movement and this is the amount of dopamine, if youre, if your at no dopamine, you don't move. Now if you increase the amount of dopamine, you also increase the amount of movement. And so we sit somewhere in some moderate place where we have movements. We got enough motor oil that we can churn our engine. But if we increase dopamine above that we would move more. And that is the situation with people who, who take for instance amphetamines. Amphetamines are going to increase the amount of dopamine, and they're going to move more. And then you are just going to see a very moving kind of person. So okay. So, that's one function is motoroil. And the second function is that dopamine facilitates. The direct pathway. So remember that the direct pathway is the way in which we choose a movement that's going to happen. And we disinhibit that movement, we release that movement from inhibition. And helping us to release that movement from inhibition is dopamine. So now let's imagine that we've lost 90% of our dopamine. What's going to happen? Number 1, we don't have the motor oil, and number 2, it's really hard to release anything from inhibition because we're not facilitated by that dopamine. So, tha, the, that is the situation with Parkinson's, and what does that feel like to an individual? What it feels like is that they, they have a very difficult time initiating movements. Once they're initiated, they're very slow. They're down here, they're slow. So it's a poverty of movement, and slow movement which is called Bradykinesia. So and how is that one way to think about this is that in fact what's really what's really slammed in Parkinson's is chunking is habit movement. Movements that are habits. And so instead of being able to do something, just re-do it quickly. Now you have to do each component movement. And I just want to show you some, or, share with you some quotes from a blogger. And this is a nurse scientist, who, who has Parkinson's. And this individual writes I have made allusions several times on the blog about the strange subjective experience of slowly losing control I am particularly fascinated by the freezing. Freezing, that is a very act way to describe Parkinson's. The freezing I experience sometimes. I attempt to lift my hand from what it's doing and it just doesn't want to go along. I have to put effort, even focus or concentration into getting it to move. This is to such a degree that I have to pause whatever else my brain is doing. There's no. Multitasking in anyway. After pause, whatever else my brain is doing, including talking or thinking. In order to get this motor action to go I must confess sometimes when no one else is around, I will just grab my hand with the other hand and actually move it. I describe it this way to emphasize that sometimes movement for me requires mental effort. So mental effort is the opposite from habit. As opposed to physical effort. For many people, particularly older folks, Parkinson's advances to such a degree that it takes all the focused will they can muster to move a few steps. Some day in the distant future that may be me. so, so what this really highlights is that in a situation of Parkinson's there is a, a need for deliberate movement of every component action. It's as though all the possibility of habit were taken away and everything had to be done deliberately with thought. This makes for very slow moving. In the next segment we're going to consider what this kind of, circuitry might mean for other types of brain functions, such as thought, mood, and perception. [MUSIC]
