Monday, September 22, 2008


I’m reading about the limbic system, which is also called by the rather romantic name “the paleolithic brain” though it is traceable back to the tetrapods, which preceded the reptiles and dinosaurs. Basically, it’s a collection of structures under the jello of the cerebrum and the cerebellum and it’s older. But the first thing one finds out about the limbic system is that there’s no agreement that this collection of structures is actually a “system” at all. There are maybe fifteen little gizmos that seem to be the Operating System (to use computer terms) rather than the “thinking” or the “mechanical” parts of the brain.

Working together somehow, they do the processing, or a big part of it, that tells you where you are, what to remember, and how to feel about it. They seem to mediate between the chemical systems, molecules in solution, and the actual structures like the long “wires” of the sympathetic and parasympathetic nerve system that carry electrical charges to control the machinery of breathing, heartbeat, temperature control, and so on. They connect the brain and the neural network embedded in the tube walls of the guts that one scientist calls “the second brain.”.

But they are so subtle and small that arguments abound about whether they are the edges of larger anatomy or clusters of small centers. Experiments can determine what sends signals into and out of them, and what happens if you destroy one of these little bits, but not why. It’s sort of like chlorophyll -- we know what it does and when it does it but, until recently anyway, no one knew exactly how it changed sunlight into plant stuff.

Take the amygala. (No don’t! I really NEED it!) Two almond-shaped bits sort of behind the eyes. Recent stories about it have sensationalized the phenomenon that toxoplasmos parasites (little worms) will target and infest the amygdala in rats, with the result that they lose their fear of cats. Which means cats can eat the rats easier, so then the parasite eggs leave the cat in cat poop which dries, powders and is inhaled by... rats and us. (I have no fear of cats! Aaauugh!)

You remember all those warnings to pregnant women not to empty the cat’s litter box? That’s because the toxos also like to colonize fetuses. And they like eyes. When I was doing animal control education, my counterpart in Seattle told me that her young daughter remarked that something was crossing her line of vision -- IN her eye! It was one of those little worms. How do you get it out? You don’t, but there are medicines (I think) that will make it die and then be resorbed into the system.

One of the phenomena of a destroyed amygdala is a mother who abuses and neglects her baby. It’s impossible not to think of the young Native American mother, prone to rage attacks, who killed her baby last May and stashed the body in the trunk of her car where it was found only weeks ago. How do we distinguish between people who have holes in their brains from people who are ornery from people who are evil? By definition they may all be insane, not-sane. The difference is in the way we treat them once we know what the problem is. Punishment will not bring back a missing brain part and neither will therapy nor religious exhortation.

In some states one must have certain blood tests before marrying, to assure the health of the ensuing children. No one tests for toxoplasmosis. Anyhow, people don't wait until after marriage to have children. Would we be justified in sterilizing any woman who has a destroyed amygdala? Would we be justified in destroying all the cats? Five young men in Montana have just been arrested for torturing and killing dozens of cats. What is the state of their amygdalas? Two others killed their own babies by shaking, striking and wrenching them. What about them? Surely there are no funds for MRI’s for these people.

When I googled for “amygdala toxoplasmosis,” the top of the list was a website proclaiming the importance of “the majority,” meaning whites, probably male and English-speaking, and the necessity of barring immigration of parasitized people from third world countries. Simple curiosity about the brain can turn pretty nasty in a hurry. There’s a lot of junk science out there, and not just creationism. Is there a parallel to the anatomy of the brain in society -- can a social amygdala be missing?

But we want to know how brains work because it becomes clear that our brain operating systems affect who we are in rather direct ways. Dysfunctional amygdalas seem to have something to do with “borderline personality disorder,” paranoia, and bipolar disorder, as well as depression. I put “borderline personality disorder” in quotes because someone said I had it. So I bought a pile of books and read up on it, but it seems to be a junk category that means “I don’t much like you because you don’t do what I say.” In short, stay away from anyone who says you have it: it’s probably a projection of THEM. In the Great Falls Tribune there is occasionally an advertisement by a man who claims he can cure “oppositional defiance disorder” in children. Judging from his picture, I tend to suspect that electrical cattle prods are involved. He says he can “cure” it because he once had it.

On the other hand, if my amygdala isn’t quite functioning properly, I want to know about it. These two little tissue buds seem quite susceptible to drugs, including those that alleviate depression. The amygdala has mostly been studied through conditioning: shocking rats or giving them pellets to “teach” them. What you look for is what you find, so what the experiments have often revealed is unconscious fears like PTSD or anxious reactions to angry faces. No one has managed to figure out how to test or affect the various named nuclei WITHIN the amygdala to see what THEY do as separate little bits. It’s like particle physics: every time you find a teeny building block, it has even more teeny parts it can be broken into.

Mostly what a person finds out about brains is that no one knows much -- just enough to make us all more curious. But maybe it teaches us something about being sceptical and also compassionate.


Anonymous said...

No deep thoughts from this quarter; but, want you to know that the posting is appreciated!
Cop Car

Mary Strachan Scriver said...

Thanks! I see references over and over to "limbic" and "amygdala" and other parts. But I'm finding that there are at least fifteen little structures that may or may not be part of the "limbic system" and some people don't think they even amount to a system! So much to learn! Yet this set of brain bits seems to hold much of our individual personalities.

Prairie Mary

Bessa said...

Was looking for the correct meaning of paleolithic brain and found your post. A good start point to the post I am writing on why are we so crazy about easter chocolate eggs. Congratulations!