Viraj's Weblog

The above picture is from a BBC show about violent behavior in humans. I found it hilarious. Scientists did a study and found that murderers had lower brain activity (glucose metabolism) in the prefrontal cortex. They say this correlates physical differences in brain structure to different types of behavior, notably violence. I can see it now, brain scanners at airport security checks. A flashing red evil light would blink whenever such a person came through. Then they could be re-routed to the psychotic plane, or short-plane, like the short-schoolbus for mentally challenged kids. Can we really dilineate a murderer from a normal person with such scans? It seems rather simplistic to me.

There are all sorts of experiments on violent behavior. The show claimed that low serotonin levels and high dopamine levels in the brain directly contribute to violence. Serotonin acts as an inhibitor, to stop feelings and thoughts from getting out of control. Dopamine is just the opposite. So scientists are searching for genes regulating those chemicals, and one such gene is the one encoding MAO-A. Studies have found that not enough MAO-A could contribute to violent behavior, because it results in lower serotonin levels. But if the MAO-A gene is expressed, there is more serotonin, and there is less tendency for violence.

So what makes the gene expressed? Nurturing. It turns out if a child is nurtured by his mother and is taught at an early age about social bonding, love, bad behavior vs good behavior, the child has a less tendency to grow up with problems. Take the same child and rear him without motherly love and he or she is more likely to turn out problematic. Is this really surprising? No, but to me the environmental influence on genetics is. There is a chemical basis to the behavior. Someone predisposed genetically to a certain behavior, or even disease, can in effect cancel out, or amplify, a gene based on their experience.

This is one of the many examples where genetics by itself cannot determine anything without also considering the experiences of the person. The person's experience itself determines whether the gene is expressed or not, and it ultimately shows that the brain can control gene expression. I find that rather amazing, and it shows the true power of the brain. It's not too hard to fathom the brain having control of other disease-related genes. Let's say you have a gene that predisposes you to cancer. Is there a possibility the brain can control whether that gene is expressed or not? I don't know, but it's interesting to think about.