Key Research: Raine, Buchsbaum and La Casse - Brain abnormalities in murderers indicated by PET scans Flashcards
What were the main aims of Raine’s study?
To look at brain function using PET scans on a group of murderers and see if they have different brain activity to ‘normal’ people.
Outline the experimental group.
- 41 participants
- Charged with either murder or manslaughter and were pleading Not Guilty by Reason of Insanity (NGRI)
- Sent to University of California Imaging Centre
Outline the control group.
- 41 people
- Matched age and gender to murderers
- 6 murderers with schizophrenia matched with 6 schizophrenic controls
What were the three main reasons why the murderers were sent to the imaging centre?
- Obtain evidence to see whether they were NGRI
- Find out if they were competent to understand judicial system
- See if there was any evidence of diminished mental capacity
How long before the experiment were participants kept medication free?
2 weeks
What were participants allowed to do before they were injected with dye?
They were allowed to practice the continuous performance task (CPT) which required them to search for targets on a screen and pres a button to indicate when the targets were spotted.
What were participants injected with?
Fluorodeoxyglucose (FDG) - A radioactive tracer to trace the metabolism of glucose by the brain.
How long did participants do the CPT task for?
32 minutes
What did the participants do after the CPT task?
They went to the PET scanning room and their brain was scanned to measure brain activity in the cortical and sub cortical regions.
What results were found to do with the cerebral cortex? (pre-frontal cortex)
-Lower acitivty in murderers than controls - linked to loss of self-control and altered emotion
What were the results to do with the corpus callosum?
-Lower activity in murderers than controls - may stop left brain inhibiting the right’s violence
What were the results to do with the subcortical areas (limbic system - amygdala)?
- Lower activity in left side of brain in murderers
- Limbic system thought to control emotional expression - may cause lack of inhibition for violent behaviour
What are the main conclusions of Raine’s study?
- That reduced activity in the prefrontal cortex may explain impulsive behaviour, loss of self-control, immaturity etc
- Shows some murderers have different brain functions to normal people
