Raine et al's Study

to show that murderers pleading NGRI would show dysfunction in the areas of the brain associated with violence such as amygdala.

Experimental group: 41 murderers (39m and 2f) pleading NGRI due to reasons such as schizophrenia, brain injury, substance abuse. They had a mean age of 31.3 years.

Control group: 41 people (39m and 2f) who were matched with the experimental group on age, gender, diagnosis of schizophrenia. Their mean age was 31.7 years. 

Participants were screened for their general health, medical history and had to undertake psychiatric interviews. All participants were medication free for two weeks prior to the brain scan and consented to take part.

• participants worked on a continuous performance task (CPT) focusing on a presentation of blurred numbers.
• They had a 10-minute trial of the CPT ensuring they knew what to do.
• They were injected with a radioactive tracer and had to complete the CPT for 32 minutes to allow the tracer to be metabolised in the active areas of the brain.
• After they completed the task, they had a PET scan of their brain. 

In the cortical areas, the NGRI's brain scans showed:

• lower activity in prefrontal cortex (self-control, remorse)
• lower activity in parietal areas than control group (verbal ability, educational underachievement)

In the subcortical areas:

• lower activity in corpus callosum (passing information between hemispheres)
• asymmetrical activity in amygdala with lower activity on the left and higher on the right than the control group. (impulsivity and emotion)

There was no difference between the two groups on how well they did on the task and individual differences were found not to be affecting the results.

Deficits in the functioning of the pre-frontal cortex, problems with different areas of the subcortical areas could explain violent criminals as they are unable to learn from the consequences of their actions.

The asymmetric functioning of the amygdala and hippocampus may be implicated in misunderstanding of social situations which could also lead to inappropriate reponses, aggression and violent behaviour.