neural and hormonal mechanisms in aggression

• the 3 neural explanations of aggression are:

  • limbic system
  • amygdala
  • orbitofrontal cortex and serotonin
• researchers linked the limbic system to the regulation of emotions such as aggression. The system includes the hypothalamus, amygdala and hippocampus
• the more reactive the amygdala is to the environmental threats the more likely that aggression will be shown. REserchers used brain scans with participants in a lab based game that provoked aggression. Aggressive reactions were associated with a fast and heightened response by the amygdala. Benzodiapines decreased amygdala activity
• normal levels of serotonin in the orbitofrontal cortex inhibit neurones and are linked to greater behavioural self-control. Decreased serotonin disturbs this mechanism, reducing self-control and increases impulsive behaviours
• the 2 hormonal mechanisms in aggression are:

  • testosterone
  • progesterone
• testosterone helps regulate social behaviour via influence on brain areas involved in aggression. Males are more aggressive towards other males at 20+ years when testosterone levels peak. Researchers found a positive correlation between testosterone and aggression with histories of impulsively violent behaviour
• animal studies show that aggression is linked to testosterone as removing testes reduces aggression in many species. Injecting testosterone restores aggressive behaviour
• progesterone levels vary in menstrual cycle (lowest during and just after menstruation). There is a negative correlation between progesterone levels and self-reported aggression
• One limitation of the limbic system is that non-limbic brain structures are also involved. Limbic structures function jointly with the non-limbic orbitofrontal cortex. This is involved in impulse-regulation and inhibition of aggression. Researchers claim orbitofrontal cortex activity is reduced in psychiatric disorders featuring aggression which disrupts the orbitofrontal cortex’s impulse control function increasing aggression. This shows that the neural mechanism in aggression is more complex
• One strength of serotonin is that there is research on the effects of drugs on serotonin. Researchers got participants to take part in a lab based game, giving and receiving electric shocks in response to provocation. Participants who took paroxetine consistently gave consistently fewer and less intense shocks than a placebo group. This is evidence that there is a link between aggression and serotonin
• One limitation of testosterone in aggression is that the evidence linking testosterone and aggression is mixed. Two researcher‘s dual hormone hypothesis suggests high levels of testosterone leads to aggression but only when cortisol levels are low. High cortisol blocks testosterones influence on aggression. Cortisol is the key to the body’s chronic stress response. Therefore the combined activity if testosterone and cortisol may be a better predictor of aggression than either hormone alone