Neural and hormonal mechanisms in aggresssion

Question 1

What are the neural mechanisms in aggression

Answer 1

Overresponsive amygdala (limbic system)/Reduced serotonin in orbitofrontal cortex

Question 2

What does the limbic system consist of

Answer 2

Papez/Maclean said hypothalamus/amygdala/parts of hippocampus

Question 3

Study of overresponsive amygdala causing aggression

Answer 3

Gospic et al (2011): pps provoked
When aggressive FMRIs showed fast/heightened response of amygdala

Question 4

Study of overresponsive amygdala causing aggression (benzodiazepine)

Answer 4

(Drug that reduces arousal of autonomic nervous system)= Decreased amygdala activity/aggression

Question 5

Role of reduced serotonin orbitofrontal cortex in aggression

Answer 5

Normal levels= reduced firing of neurons= greater behavioural self-control
-So deficiency disrupts this mechanism= + impulsive behaviour

Question 6

Study of reduced serotonin in orbitofrontal cortex causing aggression

Answer 6

Virkunen et al (1994) compared levels of a serotonin breakdown product in violent impulsive/violent non-impulsive offenders
-Found much lower levels in impulsive

Question 7

Hormonal mechanisms in aggression

Answer 7

Heightened testosterone for men/reduced progesterone for women

Question 8

What is testosterone and why is it thought to cause aggression

Answer 8

Androgen/role in developing masculine features
-Men + aggressive than women
-More aggressive to other men when testosterone highest (after 20 years)
-Influence on certain areas of brain implicated in aggression

Question 9

Animal studies in testosterone causing aggression

Answer 9

Giammanco et al 2005: Castrated animals= less aggressive, injecting testosterone restored

Question 10

Human studies in testosterone causing aggression

Answer 10

Dolan et al 2001: Positive correlation of testosterone-aggressive behaviour in 60 inmates with history of violence

Question 11

Role of progesterone in women aggression

Answer 11

-Lowest just after menstruation
-Ziomkiewicz et al (2012)= - correlation in progesterone levels-aggression
-So low progesterone= + aggression

Question 12

Weakness of limbic explanation

Answer 12

Research that non-limbic brain structures also involved
-e.g Coccaro et al (2007)= orbitofrontal cortex activity reduced in aggressive mental disorders as OFC impulse control function disrupted
-So neural regulation more complex than just amygdala

Question 13

Strength of serotonin explanation

Answer 13

Research into effects of drugs
-e.g Berman et al (2009) got pps to give shocks after provocation
-Half given drug paroxetine (increases serotonin)/others given placebo
-Paroxetine gave fewer/less intense shocks

So casual link between serotonin function and aggression

Question 14

Strength of hormonal explanation

Answer 14

Research into role of testosterone in range of animal species
-E.g Giammanco et al (2005): Male rheus monkeys= + testosterone/aggression in mating season
-Castrated rats killed less mice
-Female rats injected with testosterone killed more mice

Question 15

Weakness of hormonal explanation

Answer 15

Carre/Mehta (2011) dual-hormone hypothesis= High level testosterone causes aggression but only when low cortisol
-Cortisol= central role in body’s response to chronic stress