Classic biological psychology - Raine et al. (1997)

Yo,

Here's a summary:

Aims: To show that the brains of murderers who pleaded not guilty by reason of insanity were different from the brains of non-murderers. Raine et al. Investigated whether brain dysfunction predisposed people to violent behaviour.

Background Literature: Previous studies linked certain parts of the brain to violent behaviour-

Ø  EEGs, neurological and cognitive testing suggest that there is a link between brain dysfunction and violent behaviour. The prefrontal cortex and different functioning of the two hemispheres are thought to be important.

Ø  Recent mapping techniques have found reduced electrical activity in the left angular gyrus in violent offenders
Ø  Some experimental animal research suggests that the limbic structures (amygdala and hippocampus) and the thalamus are involved in aggression.

Raine listed these regions and studied them both in murderers pleading not guilty by reason of insanity and in a control group. A preliminary study of 22 murderers and 22 ‘normal’ participants gave some support for prefrontal dysfunction in the murderers.

Procedure: There were 41 murderers pleading not guilty by reason of insanity and 41 controls.

There were 39 men and 2 women who had been charged with either murder or manslaughter. Average age was 34.3. All had been referred to the university of California Irvine Imaging Center to obtain evidence relating to a ‘not guilty by reason of insanity’ defence or to gather evidence for some other part of their trials to do with incompetence.

 The group consisted of 23 people with a history of brain damage, 6 schizophrenics, 3 people with a history of substance abuse, 2 had an affective disorder, 2 had epilepsy, 3 were diagnosed as hyperactive or with a learning disability and 2 had paranoid personality disorder. None were on medication.

The control group was formed by matching each murderer with a normal participant of the same sex and age, and who was similar in other ways, e.g. There were 6 schizophrenics. None of the control group was on medication. The group consisted of 39 males and 2 females (average age 31.7).

PET scanning procedure: The procedure of the study was as follows..

Ø Each participant carried out a practice test

Ø 10 minutes later, a fluorodeoxyglucose (FDG) trace was injected

Ø The participant then completed a continuous performance task and target recognition was recorded

Ø After a 32 minute period of FDG uptake, the participant was taken for a PET scan of the head and images of slices of the brain were produced

Brain regions were identified by:

Ø The cortical peel technique- slices were examined and glucose values for each region of interest were compared with those of other areas in a slice

Ø A box technique- 2cm² boxes of brain area were examined and linked scan results to the suggested areas for violence

Results: In the tasks carried out before the PET scan there were no differences in performance between the two groups.

Cortical Regions	Sub-cortical Regions
Prefrontal lobe- the murderers had lower glucose metabolism in comparison with controls in some areas	Corpus callosum- murderers had lower glucose metabolism than the control group
Parietal lobe- the murderers had lower glucose metabolism than the controls, particularly in the left angular gyrus and bilateral superior parietal regions	Amygdala- murderers had reduced activity in the left amygdala and greater activity in the right amygdala than the controls
Temporal lobe- no significant differences between the groups	Medial temporal lobe (including hippocampus)- murderers had reduced left activity and greater right activity than controls
Occipital lobe- Murderers had higher glucose metabolism than controls	Thalamus- murderers had greater right thalamic activity than controls

Raine et al. (1997) also looked at other variables where the groups differed that may have affected results. They checked right/left handedness and found that this would not have affected results. They checked ethnicity and found no significant differences. They checked for head injury, 23 murderers had history of head injury, this seemed to lower activity in the corpus callosum.

Conclusions: It was concluded that murderers pleading not guilty by reason of insanity have-

Ø Reduced glucose metabolism in the bilateral prefrontal cortex, the posterior parietal cortex and the corpus callosum

Ø Abnormal activity in the amygdala, thalamus and medial temporal gyrus, including the hippocampus

 

These findings support the idea that violence has biological causes.

Ø Prefrontal deficits can result in impulsivity and loss of self-control, as well as emotionality and an inability to modify behaviour

Ø Limbic deficits show the amygdala is associated with aggressive behaviour, both in animals and humans. The amygdala, hippocampus and prefrontal cortex govern the expression of emotion and the thalamus relays information. The hippocampus is thought to modulate aggression (in cats) and there is other evidence linking the limbic system to aggression, emotion and control

Ø The posterior parietal cortex seems to be linked to cognitive functioning. For example, reductions in glucose metabolism in the left angular gyrus have been correlated with reduced verbal activity. Cognitive dysfunction could mean educational and occupational failure, which may lead to crime and violence

Ø A dysfunction in the corpus callosum may explain hemisphere differences because the corpus callosum links the two hemispheres. The right hemisphere has been said to generate negative effects in humans and may be in the murderers less regulated by the right hemisphere. Studies of rats reinforce this idea.

 

Findings show that neural processes underlying violence are complex and that there is no single mechanism in the brain that causes violence. ‘Violent behaviour probably involves disruption of a network of multiple interacting brain mechanisms that predispose violence in the presence of other social, environmental and psychological predispositions’.

Overall, murderers pleading guilty by reason of insanity seem to have different brain functioning from controls.

KOP!