Raine et al. (1997): Brain Scan Study

• Raine et al. (1997) used PET scans to investigate brain differences between murderers and non-murderers.
• The aim was to examine dysfunctions in brain areas associated with aggression, impulsivity, and emotional regulation.

Procedure

• Participants included 41 murderers (39 males, 2 females) pleading Not Guilty by Reason of Insanity (NGRI).
• A control group of 41 non-murderers was matched for age and sex.
• Participants were given a continuous performance task (CPT) to stimulate brain activity related to attention and reaction.
• A fluorodeoxyglucose (FDG) tracer was injected to track glucose metabolism (brain activity).
• PET scans measured brain activity, comparing murderers (NGRI) to the control group.

Findings

• Murderers had lower prefrontal cortex activity, linked to impulse control and decision-making.
• Dysfunction in prefrontal cortex activity could explain increased impulsivity and aggression.
• The amygdala, hippocampus, and thalamus showed reduced activity in the left hemisphere, and higher activity in the right hemisphere of the murderers' brains.
• Abnormal amygdala activity may contribute to a lack of emotional regulation.
• Reduced activity was found in the corpus callosum, which may impair communication between rational and emotional brain areas.
• No significant differences were found in the cerebellum and occipital lobe activity between the two cohorts.

Conclusion

• Brain abnormalities may be linked to increased aggression and violent behavior.
• Reduced prefrontal cortex activity and abnormal limbic system functioning could explain poor emotional regulation, impulsivity, and aggression.
• The study suggests a biological basis for violent crime, but biology alone does not determine criminal behavior.

Strengths of Raine et al. (1997)

• The use of PET scans provides objective and quantifiable measurements of brain activity with high scientific validity.
• Standardized procedures, like the continuous performance task (CPT), increased internal validity.
• A matched control group minimized individual differences as confounding variables.
• The study has real-world applications in understanding biological risk factors for violent behavior.

Weaknesses of Raine et al. (1997)

• The sample consisted of murderers pleading NGRI, is a specific group and reduces the generalisability.
  • The sample discounts premeditated murderers, non-violent criminals, and has low female participation.
• The laboratory setting has low ecological validity.
  • The CPT task does not reflect real-life decision-making, emotional regulation, or violent behavior.
• PET scanning technology used in 1997 is now less precise than modern neuroimaging techniques such as fMRI.

Linking Brain Structure to Aggression

• Aggression is linked to specific brain structures involved in impulse control, emotional regulation, and decision-making.
• Reduced prefrontal cortex activity leads to poor aggressive impulse control, making individuals more likely to act violently without considering consequences.
• Overactivity in the amygdala is associated with increased aggression, and can cause individuals to misinterpret threats and react impulsively.
• Hippocampus dysfunction impairs one's ability to regulate aggressive responses based on past consequences.
• Reduced activity in the corpus callosum results in poor aggressive tendencies regulation as a result of a struggle to balance emotional reactions with logical thinking.

Synaptic Transmission

• Synaptic transmission is the process by which neurons communicate.
• An electrical impulse triggers the release of neurotransmitters into the synaptic cleft.
• Neurotransmitters bind to receptor sites on the postsynaptic neuron, continuing the signal.
• Excitatory neurotransmitters increase the likelihood of neuron firing, while inhibitory neurotransmitters reduce it.
• Excess neurotransmitters are reabsorbed (reuptake) or broken down by enzymes after transmission.

Strengths of Using Brain Structure as an Explanation of Aggression

• Brain structure explanations are supported by neuroimaging studies and increase reliability.
• These findings are based on objective brain scans, which reduces subjective bias.
• Understanding the brain structures involved in aggression can help develop interventions or medication targeting brain dysfunction.
• Treatments that regulate amygdala activity could help reduce aggression in individuals with impulse control disorders.