Neural mechanisms

• Papez (1937) and Maclean (1952) - AO1


  - The first attempt to link the limbic structures to emotional behaviours such as aggression

  - Identified limbic system including hypothalamus, fornix, amygdala and cingulate gyrus

  - Most important structure is the amygdala

  - Speed and sensitivity of the limbic system responses to stimuli which is an important predictor of aggressive behaviour in humans
• The reactivity of the limbic system...

  predicts aggressive behaviour
• Amygdala...


  is strongly associated with aggression

  - Plays a key role in how were interpret and respond to environmental threats
• Gospic et al (2011) - AO1

  • Carried our brain scans using an fMRI machine on participants when playing lab-based game which provoked aggression
  • Scans showed aggressive reactions were associated with a fast and heightened response by the amygdala
• Benzodiazepine


  - reduces arousal of the autonomic nervous system

  - in Gospics ultimatum game found that it halved the number of rejections towards the proposal and decreased the activity of the amygdala
• Serotonin - AO1


  - Neurotransmitter with widespread inhibitory effects throughout the brain.

  - Key role in aggressive behaviour

  - It slows down and dampens neural activity
• Normal levels of serotonin in the orbitofrontal cortex...


  reduced firing of neurones and means greater degree of behavioural self-control
• Denson et al (2012)


  - Decreased levels of serotonin disturb this mechanism, reducing self-control and increase in impulsive behaviour including aggression
• Virkkunen et al (1994) - procedure and findings - AO1


  - Compared levels of serotonin breakdown product - A metabolite called 5-HIAA

  - Found in cerebrospinal fluid of violent impulsive and violent non-impulsive offenders

  - Levels were significantly lower in the impulsive offenders and had sleep irregulates

  - Disturbance in of this pattern implies some disruption to the functioning of serotonin
• Research into neural influences for aggression - AO1


  - Papez (1937) and Maclean (1952) - first attempt to look at structures in the limbic system

  - Gospic et al (2011) - ultimatum game - found link between response in amygdala and aggressive behaviour

  - Denson et al (2012) - decreased levels of seratinin increase impulsive behaviour

  - Virkkunen et al (1994) - sertonin breakdown products were lower in impulise and violent offenders
• AO3 research into hormonal links to aggression

  - Coccaro et al (2007) - people suffering with psychiatric disorders which exhibit aggressive behaviour have reduced activity of OFC not only the amygdala

  - Berman et al (2009) -when participants took a drug which increased serotonin activity they delivers less intense shocks compared to placebo group
• Role of other neural structures

  P - Research fails to consider the role of other brain structures.

  E - Amygdala works closely with our orbitofrontal cortex (OFC) which is thought to be involved in self-control, impulsive regulation and inhibition of aggressive behaviour

  A - Coccaro et al (2007) - people suffering with psychiatric disorders which exhibit aggressive behaviour have reduced activity of OFC. Distrusts its impulse control function leading to increased aggression

  L - Show that the regulation of aggressive behaviours is complex and involves at several neural structures
• Effects of drugs on serotonin - AO3

  P - Evidence to demonstrate the serotonin has an effect on aggressive behaviour

  E - Berman et al (2009) gave his participants enter a placebo or dose of paroxetine - drug which enhanced serotonin activity

  A - Participants took part in a lab-based game. Participants who had paroxetine gave fewer and less intense shocks than those in placebo group.

  L - This study shows link between the adequate functioning of serotonin and aggression.