12 Markers

Question 1

Describe the findings and conclusions of Raine, Buchsbaum and LaCasse’s (1997) classic research ‘Brain abnormalities in murderers indicated by positron emission tomography’.

Answer 1

Findings:
BRAIN DIFFERENCES
* Significant lower glucose metabolism in cortical regions between murderers and controls in lateral and medial prefrontal cortex in both hemispheres.
* Same for parietal glucose metabolism especially in angular gyrus.
* Identical to controls in temporal lobe glucose metabolism.
* Significantly higher on occipital lobe glucose metabolism.
* Abnormal asymmetries of activity in murderers (left hemisphere lower than right) in amygdala, thalamus, and medial temporal lobe including the hippocampus.
* Bilaterally lower glucose metabolism in the corpus callosum than controls.
* As predicted no significant differences for the amount of midbrain and cerebellum activities between murders and controls (areas linked to mental disorders).

PERFORMANCE ON CPT
* No difference in any aspect of behavioural performance on the continuous performance task (CPT).

OTHER DIFFERENCES
* Handedness, ethnicity and head injury – these not controlled for but ethnicity and head injury did not show any significant differences although left handedness 6/41 had less amygdala asymmetry and higher medial prefrontal activity than right handed murderers.

Conclusions:
* Findings cannot be taken to demonstrate that violence is determined by biology alone; clearly, social, psychological, cultural, and situational factors also play important roles in predisposing to violence.
* Data does not demonstrate that murderers pleading NGRI are not responsible for their actions, nor do they demonstrate that PET can be used as a diagnostic technique.
* Findings do not establish causal link between brain dysfunction and violence.
* Findings cannot be generalised at the present date from NGRI murder cases to other types of violent offenders.
* What these findings do document is that as a group, murderers pleading NGRI have statistically significant differences in glucose metabolism in certain brain regions compared to control subjects. They also suggest that reduced activity in the prefrontal, parietal, and callosal regions of the brain, together with abnormal asymmetries of activity in the amygdala, thalamus, and hippocampus, may be one of many predispositions toward violence in this specific group.
* Future independent replication, refinement, and extension are greatly needed.
* Any other relevant finding or conclusion from original journal article.
* Any other appropriate content.

10-12
* Description and level of accuracy of findings and conclusions is thorough.
* Depth and range included.
* Effective use of terminology.
* Logical structure.