Neural and hormonal mechanisms in aggression

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  • Neural and hormonal mechanisms in aggression:
  • AO1:
  • Reactivitiy of limbic system predicts aggressive behaviour:
  • Papez and Mclean identified the limic system as including the cingulate gyrus, hypothalamus, fornix and amygdala. 
  • Speed and sensitivity of the lymbic system responses to stimuli are important predictors of aggressie behaviour in humans. 
  • Amygdala is strongly associated with aggression:
  • The amygdala plays a key role in how we assess and respond to environmental threats.
  • Gospic et al carried out brain scans (FMRI) on participants in lab-based game that provoked aggression. Scans showed aggressive reactions were associated with a fast and heightened response by the amygdala.  Benzodiazapeine (reduces arousal of the autonomic nervous systemj) taken before the game halved the number of aggressive reactions and also decreased amygdala activity. 
  • Low level of serotonin results in reduced self-control and increased aggression:
  •  Normal levels of serotonin in the orbitofrontal cort ar inhibitory and linked with reduced firing of neurons associated with greater behavioural self-control. 
  • Decreased serotonin disturbs this mechanism, reduces self-control and increases impulsive behaviours, including aggression (Denson et al)
  • Virkkuen et al compared levels of serotonin metabolite (breakdwon byproduct, 5-HIAA) in cerebrospinal fluid of violent impulse and non-violent impulsive offenders. Levels significantly lower im impulsive offenders - disturbance of this pattern implies disruption of serotonin functioning. 
  • Testosterone is higher in men and linked to aggression:
  • Testosterone is a hormone which is responsible for the development of masculine features. It hels regulate social behavuiour via influence on areas of the brain involved in aggression. 
  • Studies of prison populations show role of testosterone in  aggression:

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