Neural Mechanisms in Aggression… It has been argued that aggression is influenced by the limbic system, a set of structures deep within the brain, but most recent research has been on the role of the amygdala and the prefrontal cortex. A01: Amygdala The amygdala is a region in the brain located deep within the temporal lobes. It is thought that the amygdala may be part of a structure responsible for emotion and aggression. This is based on a number of studies on both humans and animals. For example, research in hamsters found that stimulation of the corticomedial amygdala increases aggression and lesioning this area reduced aggression. A01: Prefrontal Cortex Another region of the brain linked to aggression is the prefrontal cortex, which is located behind the forehead at the front of the brain. Among other things, the prefrontal cortex has been linked with the regulation of correct social behaviour, and it had been proposed that the prefrontal cortex may control the amygdala. This is based on the observation that damage or reduced activity in this area can result in altered emotionality as well as a loss of control and immaturity. As a result, reduced functioning may lead to an increased likelihood in aggression.

Groves and Schlesinger 1982  The found that amygdalectomy (surgical removal of the amygdala) reduces aggression in previously violent individuals.  This supports the idea that amygdala plays a role in aggressive behaviour.  However, a side effect of this type of surgery is the loss of emotion, initiative and enthusiasm.  This does seem to suggest that the amygdala does not directly cause aggression, but is involved in processing associated emotions such as anger. Anderson 1999  He demonstrated that damage to the prefrontal cortex in infancy increases the risk of aggressive behaviour as an adult. It was also found that the risk is much smaller when damage occurs during adulthood.  This suggests damage to the prefrontal cortex may have a negative influence on social development and it is a combination of poor social development and damage to this neural mechanism that leads to aggression as opposed to damage on its own. Nature and Nurture/Alternative Approach  One problem with investigating aggressive behaviour purely on a neural level is that it ignores the role of the environment.  Researchers in Columbia have shown that watching violent programs can cause parts of your brain that suppresses aggressive behaviours to become less active. These changes to the brain could render people less able to control their own aggressive behaviour.  This suggests that our past experiences of watching violence can interact with our neural processes to create individual’s who choose aggressive responses more readily, implying a role for nurture and nature, rather than just nature. NEURAL MECHANISMS A02 Determinism  The suggestion that a person’s aggressive tendencies lie in their brains could imply a lack of control over one’s aggressive behaviours. This means a purely biological explanation is deterministic.  This has socially sensitive implications for the legal system, as studies have shown that aggressive prisoners do have such neural differences. A case could be made which questioned how far they could be deemed responsible for their crimes, which could be problematic for society. A02: Reductionism/ Wong 1997 He found reduced amygdala size and activity in violent criminals. Although this again supports the notion that the amygdala plays a role in aggression, it also seems to contradict the findings of other studies which may have suggested reducing the size of the amygdala reduces aggression. Therefore the exact role of the amygdala is still unclear.