Neural mechanisms in aggression

• Neural mechanisms in aggression

  The limbic system

  Includes hypothalamus, amygdala, hippocampus and the thalamus. The most important structure is the amygdala - key role in how an organism assesses and responds to environmental threats and challenges. Reactivity of the amygdala has proven to be an important predictor of aggressive behaviour.
• Neural mechanisms in aggression 2

  The limbic system 2

  Gospic et al. (2011) - the Ultimatum Game. Prosper offers to split money in a certain way w/ Responder. If they accept, money is split as proposed, if not, both receive nothing. Ppts played role of Responders while having their brains scanned by fMRIs. When rejected unfair offers (aggressive reaction to social provocation), scans revealed a fast and heightened response by the amygdala. Also found that a benzodiazepine drug (reduces arousal in the ANS) taken before the game halved the number of rejections and decreased amygdala activity.
• Neural mechanisms in aggression 3

  Serotonin

  Is a neurotransmitter involved in communication of impulses between neurons. Has widespread inhibitory effects on the brain; slows down and dampens neuronal activity. Decreased serotonin is linked to increased firing of neurons in the orbitofrontal cortex, which is linked to increased impulsive behaviour including aggression.
• Neural mechanisms in aggression 4

  Serotonin 2

  Virkunnen et al. (1994) compared levels of serotonin breakdown product in the cerebrospinal fluid of violent impulsive and violent non-impulsive offenders. Levels sig lower in impulsive offenders, supporting role of serotonin in reactive aggression.
• Neuronal mechanisms in aggression - evaluation

  Recent studies indicate that the amygdala does not operate in isolation in determining aggression. Appears to function in tandem w/ orbitofrontal cortex (OFC), which is not part of the limbic system. OFC is thought to be involved in self control, impulse regulation and inhibition of aggressive behaviour. This indicates that the regulation of aggression is highly complex and involves at least 3 neural structures in the brain: the amygdala, the OFC and the connection between the two.
• Neuronal mechanisms in aggression - evaluation 2

  Evidence supporting the link between serotonin function and aggression. Berman et al. (2009) demonstrated that drugs that increase serotonin levels also reduce levels of aggressive behaviour. Gave ppts either a placebo or a dose of paroxetine (enhances serotonin activity). Took part in a laboratory-based game in which electric shocks of varying intensity were given and received in response to provocation. The paroxetine ppts consistently gave fewer and less intense shocks (but only true if had a prior history of aggressive behaviour).