Can the Source of Aggression be Found in the Brain?

Can the Source of Aggression be Found in the Brain?

In Holland, male members of a certain family were found to be prone to violent outbursts; one male, criticized by his employer, attempted to run him over with a car - another raped his sister and was sent to a mental hospital - a third coerced his sister into undressing by threatening her with a knife. Such men display retarded motor development, difficulties in task planning, and awkward sexual behavior. (1). Recently, researchers claimed to have found the basis of such aggressive behavior to genetic sources - specifically, a deficiency in the MAOA gene of these males (2).

In Finland, studies were conducted on males who also displayed uncontrollable behavior, and the findings demonstrated that the men possessed a neurotransmitter substance deficiency, particularly in the messenger serotonin (3). This lack of serotonin has been linked to aggressive behavior: some violent prone individuals did not effectively break down these substances

All around the globe, people have attempted to find an organic, genetic basis for aggressive behavior. Several hormones and neurotransmitters, such as testosterone and seretonin, have been implicated in the "aggression quest", as well as specific localities of the human brain. My paper will serve to suggest that although many findings have shown impressive results regarding possible biological causes of violent behavior, we still do not have sufficient means to understand the neuroanatomical or biochemical basis of aggression.

Neurotransmitters have been suggested as a significant cause of aggressive behavior. Hans Brunner, a geneticist at the University Hospital in Nijmegen, has found that the violent male members of the Dutch family mentioned earlier in this paper, lacked a gene that produces monoamine oxidase-a (MAOA) (4). MAOA is an enzyme that breaks down significant transmitters in the brain. If the MAOA does not break down these transmitters - specifically, serotonin - then buildup of serotonin will occur and could cause a person to act violently (3).

However, it is interesting how contradictory the finding is to several other claims. Studies have shown that serotonin, in normal levels, exerts a calming, inhibitory effect on neuronal firing (5) and that, in low levels of serotonin, aggressive and impulse behaviors increase (6).This contradicts the previous claim that a built-up, or high levels of serotonin caused by the MAOA mutation, causes violent behavior.

Furthermore, the claim regarding the specificity of serotonin to aggression can be analogous to a small fish in a big pond.