Neural and Hormonal mechanisms in aggression Flashcards
What neural mechanisms affect aggression?
-Limbic system
-Orbitofrontal cortex (OFC)
-serotonin
a) Who associated the limbic system with aggression and b) what parts of the brain make up limbic system?
a) Papez (1937) and Maclean (1952) associated limbic system with aggression.
b)Amygdala, Hippocampus and hypothalamus.
How does the amygdala affect aggression
-the more responsive the amygdala, the more aggressive a person is
What did Katrina Gospic (2011) study find out about amygdala and aggression
when some patients were victim to mild provocation, they reacted aggressively there was a spike in amygdala activity measured by fMRI.
What effect did the drug benzodiazepine have in Gospic’s study?
reduces ANS arousal causing 2 effects:
1)reduced amygdala activity
2)reduced number of aggressive reactions.
How does serotonin and orbitofrontal cortex affect aggression?
-OFC linked with reduced firing of neurons which is associated with greater self-control.
-serotonin deficiency disrupts this system resulting in less self-control and leads to increase in aggression (Denson et al. 2012)
What did Virkkunen (1994) do to test how serotonin affects aggression.
-compared levels of serotonin breakdown product (5-HIAA) in the cerebrospinal fluid of violent impulsive offenders and violent non-impulsive offenders.
-Levels were significantly lower in impulsive offenders.
AO3 for neural systems on aggression
S: Drugs and serotonin: paroxetine increases serotonin and has been found to reduce aggressive behaviour. Mitchell Berman et al. (2009) gave participants either a placebo or a dose of paroxetine. Participants then played lab-based game which involved giving electric shocks in response to insults. The paroxetine group gave fewer and less intense shocks than the placebo group. This suggests a causal-link between aggression and serotonin.
L: Other brain structures: Not only the limbic system that affects aggression. The OFC is involved in impulse regulation and inhibition of aggressive behaviour. Emil Coccaro et al. (2007) OFC activity is reduced in those with disorders that affect aggression. This reduced activity causes less impulse-control function which in turn causes aggressive behaviour. This shows aggression is more complex that just the limibic systme.
AO3 for hormonal influence on aggression.
S-Animal research: Marco Giammanco et al. (2005) review of studies confirms testosterone’s role in aggression.e.g. male rhesus macaque monkeys there is an increase in both testosterone levels and aggressive behaviour during mating season. in rats, castration reduces testosterone and mouse-killing behaviour. this shows the link between aggression and testosterone.
L-Dual-hormone hypothesis: mixed evidence for the link between testosterone and aggression in humans. Justin Carre and Pranjal Mehta (2011) developed dual-hypothesis which claimed that high levels of test lead to aggressive behaviour but only when cortisol is low. When cortisol is high, test’s influence on aggression is blocked. This suggest that the hypothesis is a better predictor than aggression alone.
What hormones affect aggression?
-Testosterone: Mairead Dolan et al. (2001) found a positive correlation between testosterone levels and aggressive behaviours in a sample of 60 offenders. They had a history of aggressive behaviours and disorders - psychopathy.
-Progesterone: Anna Ziomkiewicz et al. (2012) found a negative aggression between self-reported aggression and progesterone levels. This suggests progesterone is linked with increased aggression in women.
What did Daly and Wilson (1998) find about testosterone and aggression?
found that aggression is highest to other men when testosterone is highest (after 20)
