Here are the aim, procedure, and results of Raine et al.'s study (1997) in detail:

Aim:

Raine et al. aimed to investigate whether there were brain abnormalities in individuals who had committed murder and pleaded not guilty by reason of insanity (NGRI). Specifically, the researchers wanted to identify whether violent behavior could be linked to dysfunction in specific brain regions, particularly those involved in impulse control and aggressive behavior, such as the prefrontal cortex, amygdala, hippocampus, thalamus, and corpus callosum. This study was conducted using brain imaging techniques to compare the brain activity of murderers to that of non-murderers.

Procedure:

• Participants: The study involved 41 participants (39 males and 2 females) who were charged with murder and had pleaded NGRI. These participants were matched with a control group of 41 non-murderers (also 39 males and 2 females) based on age, gender, and schizophrenia status (as 6 of the murderers were diagnosed with schizophrenia).
• PET Scan: The researchers used Positron Emission Tomography (PET) scanning to measure brain activity. This is a neuroimaging technique that provides a three-dimensional image of brain function by measuring areas of glucose metabolism.
• Task: Participants were given a continuous performance task (CPT) before the PET scan. This task was designed to increase brain activity in regions of interest. The task involved detecting targets on a screen and required focused attention and vigilance.
• Procedure for the PET scan:
  1. The participants were injected with a glucose tracer that would highlight brain activity.
  2. They were then asked to perform the CPT for 32 minutes.
  3. After the task, participants underwent a PET scan, which measured the levels of glucose metabolism in different brain regions. Lower metabolism indicates lower activity in a region.
• Regions of Interest: The study focused on several brain regions related to aggression, impulse control, and emotion, including:
  • Prefrontal cortex (associated with self-control and decision-making)
  • Amygdala (associated with emotional regulation and aggression)
  • Hippocampus (involved in memory and emotion)
  • Thalamus (relay station for sensory and motor signals)
  • Corpus callosum (facilitates communication between brain hemispheres)

Results:

• Reduced Activity:
  • Prefrontal Cortex: Murderers had significantly less activity in the prefrontal cortex compared to the control group. This region is associated with self-control, decision-making, and impulse regulation. The reduced activity suggests that murderers might have impaired decision-making abilities and reduced control over aggressive impulses.
  • Corpus Callosum: There was also reduced activity in the corpus callosum, which could suggest less communication between the hemispheres of the brain, potentially contributing to impulsivity and aggression.
  • Left Amygdala, Hippocampus, and Thalamus: Reduced activity was found in these areas on the left hemisphere. The amygdala and hippocampus are involved in regulating emotions and memory, which could affect how the NGRI individuals process emotions like fear or aggression.
• Increased Activity:
  • Occipital Lobe: There was increased activity in the occipital lobe (responsible for processing visual information) among murderers compared to controls. However, this region is not typically associated with violent behavior.
• Asymmetry:
  • Amygdala, Hippocampus, and Thalamus: Murderers showed asymmetrical activity, with lower activity in the left hemisphere but higher activity in the right hemisphere in these regions. This asymmetry might contribute to abnormal emotional processing and aggression.

Conclusion:

The study concluded that murderers pleading NGRI showed abnormal brain functioning in regions associated with aggressive behavior, impulse control, and emotional processing. These findings suggest a biological basis for violent behavior, although it’s important to note that biological factors alone do not determine criminal behavior. Environmental and social factors also play significant roles. This study provides evidence of brain dysfunction in violent individuals, but it does not prove causality between brain abnormalities and criminal actions.