Brain Structures and Aggression

• It is important to consider non-limbic brain structures in aggression in addition to limbic structures

Non-Limbic Brain Structures

• Limbic structures work together with the non-limbic orbitofrontal cortex (OFC).
• The OFC is involved in impulse regulation and the inhibition of aggression.
• Coccaro et al. (2007) suggest OFC activity is reduced in psychiatric disorders featuring aggression, disrupting the OFC's impulse-control function, and increasing aggression.
• Neural regulation of aggression is more complex than theories focusing on the amygdala

Serotonin

• Research has investigated the effects of drugs that can affect serotonin.
• Berman et al.'s (2009) study involved participants in a lab-based game where they gave and received electric shocks in response to provocation.
• Participants who took paroxetine (enhances serotonin) consistently gave fewer and less intense shocks than a placebo group.
• This study supports the idea of a causal link between serotonin and aggression.
• Neural factors can be directly linked to aggression, as shown by Gospic et al.
• Serotonin also reduces aggression by inhibiting neuronal activity.
• However, neural factors may act indirectly.
• Denson et al. found a link between serotonin and aggression, but other factors may influence this relationship.
• Evidence shows that neural mechanisms are related to aggression, but this relationship may not be direct.

Testosterone

• Research supports the role of testosterone using non-human animals.
• Giammanco et al.'s (2005) review confirms the role of testosterone to increase aggression in male rhesus macaque monkeys during mating season.
• Castration in male rats reduces testosterone levels and mouse-killing behavior.
• Injecting female rats with testosterone increases both testosterone levels and mouse-killing behavior.
• These findings indicate that testosterone plays a key role in aggression in a range of animal species.

Testosterone and Cortisol

• Evidence linking testosterone and aggression is mixed.
• Carré and Mehta's (2011) dual-hormone hypothesis suggests that high levels of testosterone lead to aggression, but only when cortisol levels are low.
• High cortisol blocks testosterone's influence on aggression.
• Cortisol is a hormone that is key to the body's chronic stress response
• The combined activity of testosterone and cortisol may be a better predictor of aggression than either hormone alone.

Animal Research

• Hormonal mechanisms in human and mammalian aggression are likely to be similar.
• Most knowledge about hormones comes from non-human studies.
• Aggression in humans is more complex than in other mammals.
• Carré and Mehta's findings about cortisol apply only to humans because cognitive factors are involved.
• Animal studies can help us understand hormonal influences on aggression.
• Findings from animal studies must be treated cautiously because human aggression is more complex.