Your brain is more than a bag of chemicals

David Anderson: Your brain is more than a bag of chemicals
So raise your hand if you know someone in your immediate family or circle of friends who suffers from some form of mental illness. Yeah. I thought so. Not surprised.

And raise your hand if you think that basic research on fruit flies has anything to do with understanding mental illness in humans. Yeah. I thought so. I’m also not surprised. I can see I’ve got my work cut out for me here.

As we heard from Dr. Insel this morning, psychiatric disorders like autism, depression and schizophrenia take a terrible toll on human suffering. We know much less about their treatment and the understanding of their basic mechanisms than we do about diseases of the body. Think about it: In 2013, the second decade of the millennium, if you’re concerned about a cancer diagnosis and you go to your doctor, you get bone scans, biopsies and blood tests. In 2013, if you’re concerned about a depression diagnosis, you go to your doctor, and what do you get? A questionnaire. Now, part of the reason for this is that we have an oversimplified and increasingly outmoded view of the biological basis of psychiatric disorders. We tend to view them — and the popular press aids and abets this view — as chemical imbalances in the brain, as if the brain were some kind of bag of chemical soup full of dopamine, serotonin and norepinephrine. This view is conditioned by the fact that many of the drugs that are prescribed to treat these disorders, like Prozac, act by globally changing brain chemistry, as if the brain were indeed a bag of chemical soup. But that can’t be the answer, because these drugs actually don’t work all that well. A lot of people won’t take them, or stop taking them, because of their unpleasant side effects. These drugs have so many side effects because using them to treat a complex psychiatric disorder is a bit like trying to change your engine oil by opening a can and pouring it all over the engine block. Some of it will dribble into the right place, but a lot of it will do more harm than good.

Now, an emerging view that you also heard about from Dr. Insel this morning, is that psychiatric disorders are actually disturbances of neural circuits that mediate emotion, mood and affect. When we think about cognition, we analogize the brain to a computer. That’s no problem. Well it turns out that the computer analogy is just as valid for emotion. It’s just that we don’t tend to think about it that way. But we know much less about the circuit basis of psychiatric disorders because of the overwhelming dominance of this chemical imbalance hypothesis.

Now, it’s not that chemicals are not important in psychiatric disorders. It’s just that they don’t bathe the brain like soup. Rather, they’re released in very specific locations and they act on specific synapses to change the flow of information in the brain. So if we ever really want to understand the biological basis of psychiatric disorders, we need to pinpoint these locations in the brain where these chemicals act. Otherwise, we’re going to keep pouring oil all over our mental engines and suffering the consequences.

Now to begin to overcome our ignorance of the role of brain chemistry in brain circuitry, it’s helpful to work on what we biologists call “model organisms,” animals like fruit flies and laboratory mice, in which we can apply powerful genetic techniques to molecularly identify and pinpoint specific classes of neurons, as you heard about in Allan Jones’s talk this morning. Moreover, once we can do that, we can actually activate specific neurons or we can destroy or inhibit the activity of those neurons. So if we inhibit a particular type of neuron, and we find that a behavior is blocked, we can conclude that those neurons are necessary for that behavior. On the other hand, if we activate a group of neurons and we find that that produces the behavior, we can conclude that those neurons are sufficient for the behavior. So in this way, by doing this kind of test, we can draw cause and effect relationships between the activity of specific neurons in particular circuits and particular behaviors, something that is extremely difficult, if not impossible, to do right now in humans...more…

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