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Aggression and the Brain

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Term Paper: Aggression and the Brain

Aggression as a general term refers to the act of inflicting physical or verbal harm with the intentions of causing pain. It is very questionable why people choose to harm each other especially if there is no reason, such as self defense, involved, but research has been evolving on that issue to show how the biology of the brain is related to aggression and how different the neurochemistry of the brain of an aggressive person to a non aggressive one. “Violent behavior never erupts from a single cause, rather it results from a combination of risk factors — among them inherited tendencies, a traumatic childhood and other negative experiences — that interact and aggravate one another” (Strueber). Basically putting together this combination of likely explanations of aggression may let one see the whole picture of why people become so aggressive. The biology of the brain and aggression seek to be explained in two different ways, in terms of androgens which are male hormones and the level of serotonin in the brain. In general it is important to talk about aggression and understand its possible manifestations because aggression is important in human existence therefore being aware of its likely biological causes will help us understand better why there is a high rate of aggression, violence and suicide and make us perceive it from the biological aspect rather than from the cultural or the individual context. First of all, the first linkage to aggression is the level of androgen in the human’s body and it has been proven that the level of testosterone increases the level of aggression in a person. Male interactions are more emphasized because of the different levels of androgens in males which therefore show that “male sex hormones play a major role in aggressive behavior” (Rosenzweig). Within discussing the male sex hormones and its effect on aggression, one thing must be taken into consideration which is sexual maturity. Because testosterone level increases when a mammal hits puberty, that emphasizes that fact that when sexual maturity takes place aggression level rise because of the increase of androgens in the body. Research was done on mice and it shows that once mice hit puberty, changes in the levels of aggressiveness took place and also took immature mice and were given sex hormones and they demonstrated a rise in their aggressiveness (Rosenzweig). In addition to that, a similar concept applies to sexual maturity is castration; it is related in the sense that castration causes a decrease in male hormones which can be identified with or similar to the mammal before they hit puberty, therefore due to castration, level of aggressiveness drops because of the diminished levels of androgens in the body (Rosenzweig). A research that they had made on women prisoners proved that “testosterone levels are highest in women prisoners convicted of provoked violence and lowest among women convicted of defensive violent crimes” (Rosenzweig). This tells us a lot because naturally in women there is testosterone so the fact that women that deliberately and intentionally commit crimes has highest levels of testosterone proves our theory even more.
Another view of the link between aggression and androgen levels can be thought of n a reversed manner, meaning that instead of it being an effect, it’s a cause. To elaborate more, basically instead of high levels of testosterone lead to aggression, it could be that aggression leads to high levels of testosterone. This is why we might think of this linkage as controversial. Confirming on this perspective even more, two things can be looked at: experience and dominance. Experience can affect testosterone levels because research was conducted on monkeys and mice and it showed that within encounters between the animals, the loser tends to have diminished androgen levels (Rosenzweig). Moreover, they have showed that testosterone levels “rises in winners and falls after sporting events and chess matches…even male fans watching a sporting event respond with either an increase or decrease in testosterone levels, depending on whether the team they are rooting for wins or loses” (Rosenzweig). The second factor that we need to look at is dominance, and this is suggested in the previous example that even in chess matches, players experience changes in their hormonal level and this is not due to the aggressiveness but dominance because it is known that chess is more of a competitive challenging game rather than it being aggressive. The second phenomena that is very important in explaining aggressive behaviors and the brain is the level of the serotonin. “Serotonin is a neurotransmitter that is produced in the raphe nuclei and is active in structures throughout the cerebral hemispheres” (Rosenzweig). There was an important study conducted where several researchers observed twenty eight monkeys that lived on an island, the researchers were basically keeping track of any aggressive behavior or recognized scars on their bodies from aggressive encounters, there were then put in order from the most aggressive to the least, serotonin levels were then measured and they found out that the most aggressive monkey had the lowest level of serotonin (Rosenzweig). This therefore suggests that there is a negative correlation between serotonin level and aggression. “Serotonin is widely believed to exert inhibitory control over aggressive behavior and intent. In addition, a number of studies of fish, reptiles, and mammals, including the lizard Anolis carolinensis, have demonstrated that serotonergic activity is stimulated by aggressive social interaction in both dominant and subordinate males” (Summers). The neurology of the brain associated with violence is another phenomenon that we should look in order for us to understand how aggression comes about within the neurology of the brain. Basically some temporal lobe seizure disorders increase the likelihood of violence in a species. Example of a man that murdered several of his family members, when postmortem analysis was done on his brain, it was found out that he had a tumor deep in his temporal lobe. Other data relieved the occurrence of aggression in temporal lobe seizure patients and that habitually aggressive criminals display abnormal EEG’s that indicate temporal lobe disease. Temporal lobe disorders may underlie many forms of human violence and produce a disorder that is labeled dyscontrol syndrome.
Other research has linked violence in humans with some form of seizure disorders or other clinical neurological pathology. Also studies were conducted that showed that there
Another explanation that coule be made about the neurology of the brain and violence is the “frontal brain hypothesis.” Basically this hypothesis suggests that damage to the prefrontal cortex tends to be greatly linked with high levels of aggressiveness. have discovered that Vietnam War veteran who suffered damage to the prefrontal cortex tend to be more aggressive. Similarly, adult patients who have frontal brain lesions are generally more uninhibited, inappropriate and impulsive — much like people with antisocial behavior disorders. In these adult groups, however, there is no direct indication that their brain damage predisposes them to actual violence.
Another interesting thing was found out by many neuroscientists, basically they have clearly noticed that in the limbic system and the prefrontal cortex (which are associated with control of emotions) ther were changes in the “anatomical and pshyciological differences in both the limbic system and the prefrontal cortex” (Struber). Among violent offenders, neuroscientists have found anatomical and physiological differences in both the limbic system and the prefrontal cortex, brain regions that are involved in the development and control of emotions. Some scientists propose that the orbitofrontal cortex, a region of the prefrontal cortex where decision making takes place, inhibits areas of the limbic system — specifically the hypothalamus and the amygdala, primitive brain regions that are a source of fear and aggressive impulses.

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