"Under Construction". I need some more images and this is "on hold".
[What follows here is a section that doesn't really show what I want, which is to help you see the "caudate" as it is playing a role in obsessions. You can look at what I've got so far, if you wish. It doesn't really work yet because the images I'm using here don't match up right. Save it for later. Put yourself on the "email updates" list and you'll be informed when this chapter is complete -- or at least more complete. I will be adding sections from time to time as more studies and good illustrations come along].
You'll remember that the R complex is the "housekeeping brain" we all have, in addition to our limbic system and our cortex. Now imagine you had a brain that could get "stuck" on one housekeeping task, like cleaning or checking safety or organizing. Some people are like that, as you probably know. They can get stuck for an hour washing their hands; or checking the emergency brake on the car; or organizing the kitchen before they start cooking. Imagine we could get Oscar, who has just this brain problem, in a PET scanner while he was "stuck" like that. Some part of this "housekeeping brain" ought to show up on the scan as abnormally active, right?
Well, a research team from UCLA has done just that. Here's Oscar worrying about whether he really set the emergency brake.
Whoa! All right, let's get organized here. This will be the trickiest brain structure we've tried to look at yet. You might prefer to work your way through Tours 1-4 before you try what follows here, because the 3-dimensional nature of the structure involved (the "caudate") makes interpreting the picture above rather difficult.
You may have recognized this as a PET scan, although it's less clear because it's an old version, and it is shown in a view you haven't seen before. Let's look at the structure it illustrates first, this "caudate" thing, and then look at the caudate itself from just the same point of view as this PET scan -- then, we'll return to the scan and talk about what it means.
Go to Tour #1 if you haven't learned about your 3 brains yet. Follow the signs to the "R complex" tour and take that too: you'll need that basic introduction to the "basal ganglia". From those tours, you'll remember the "caudate". Here it is again, at the arrow:
Now, let's take Oscar, who's all dressed up for work.
You may have taken the Tour in which we were looking at Cindy's right brain half after her left half went to lunch. Well, imagine this time Oscar's fairy godmother waved her magic wand the other way, and Oscar's front half went off for dinner. We're looking at what's left behind to write grant applications (ignore the white-circled structures; you may have seen them on the amygdala Tour):
When Oscar was all there, you were looking at his eyes; now you see this? Look at it this way: you were looking in through the windshield of a car, and now the car's been split into a front half and a back half just behind the front seats. Where you would have seen the top of the steering wheel, and the two front seat passengers; you now see the back seat people and the window behind them. In the medical lingo, this is called a "coronal section". If that's not making any sense to you, hang on, another way of looking at it is coming up next.
The gold circles in the picture above are, believe it or not, a portion of that gold arch we called the caudate. Remember that? Here it is again:
Imagine we took off the front half of this brain, the part in front of the gold line, and then looked at it from the front. You'd see that top half of the caudate right near the middle (and since there are two of them, one on each side, you'd see two ovals, one on each side right near the middle of the brain). And the amygdala, which is also cut by the gold line, would also be visible. That's what the MRI above shows. Here it is again. See if you can make sense to the two different views (side and front):
If you've "got it", you'd understand that viewed from in front like this, the caudate is "coming toward you": there is more of it, and as it comes toward you from the computer screen, it would even get bigger, because the "head" is fatter than the arch farther back. Imagine a view from the front like this closer to the front of Oscar's head: the two caudate parts, still near the center of the head, would be even bigger, more like the diameter of the thicker gold line above. In MRI views, you imagine you're looking at Oscar himself, so the thicker gold caudate above is his right one. We'll now look at that same spot -- Oscar's right caudate, near the head of that structure -- using a different camera.
To see the R brain at work we need to watch someone really extremely active on some housekeeping task. Unfortunately, there's a mental illness like that, called "obsessive compulsive disorder". Part of the function of these basal ganglia is to make sure something got done. It's like their job is to continually go back and make sure you didn't leave anything in your hotel room. And that goes for any "housekeeping" activity you do. Did you really wash your hands well enough? Did you really remember to lock the door?
If somebody has "obsessive compulsive disorder" (OCD) they can get stuck in this "really?" questioning. The French call it folie de doubt -- a mental illness of doubting. We caught Oscar stuck in such a loop, so we could see what parts of his brain are overactive (well, the UCLA OCD research team did Schwartz et al). That's how his picture was taken, in the UCLA PET scanner.
Now, what's too active here?. Well, to see that we need a "normal" case with which to compare. We'll use Oscar after he got better with treatment as the "normal case", to make sure we're comparing Oscars with Oscars.
Notice that just to the left of the middle of Oscar's head there's a yellow "dot" in the pre-treatment scan that's almost but not quite gone in the after-treatment scan. See that? That dot is part of the R brain, a part of the "basal gangia" called the caudate nucleus. You are seeing a treatment stop that nucleus from being so active. (We'll get to what treatment that was in a moment). Here is a drawing of Oscar's basal ganglia.