Raine et al - Classical study for aggression Flashcards
What are the 2 aims of Raine’s study?
- To use brain scanning tech to identify brain impairments in ppl charged with murder who have pleaded not guilty by reason of insanity (NGRI)
- Hypothesised brain scans would show dysfunctions in areas linked in previous research to violence - prefrontal cortex, amygdala, corpus callosum, hippocampus, thalamus
What was the sample of the control + experimental group?
Experimental = 39 men + 2 women charged with murder or manslaughter, mean age 34.3 years
Control = 39 men + 2 women, mean age 31.7 years
All from California + tested at Brain Imaging Centre at University of California
What are some reasons for testing the experimental group?
- Schizophrenia (6)
- History of head injury or organic brain damage (23)
- Epilepsy (2)
- History of psychoactive substance abuse (3)
What were all ppts not receiving during PET scan?
Medication, + had to be medication-free for 2 weeks before scans
Consent gained
How was the control group formed?
By matching each murderer with normal ppt of same sex + age, who’d been tested using identical PET scan procedures in same lab
E.g. Schizophrenic murderer matched with normal schizophrenic person
Matched pairs
How were the controls screened for health? And what were the results?
By physical exam, medical history, + psychiatric interview
No subject taking meds, had history of psychiatric illness in self or relatives, or had medical illness
What subjects were excluded?
Subjects who had seizures, head injury, + substance abuse
What was the PET scan procedure? (FDG uptake)
- FDG tracer injected into subject in test room
- For 32 mins, subject completed continuous performance task (CPT)
- 10 mins before injection, ppts given practise trials on CPT
- Task started 30 secs before injection so initial task wouldn’t be FDG labelled
What was the PET scan procedure? (after FDG uptake)
- After 32 mins of FDG uptake, subject transferred to PET scanner room
- Individually molded plastic head holder held head in place during scan
- 10 slices at 10 mm intervals parallel to canthomeatal line were obtained
What were the 2 techniques the brain regions were identified by?
- Cortical peel technique
- Box technique
What were the results for the prefrontal, parietal, and occipital lobes? (cortical regions)
Murderers had lower glucose metabolism than controls
Murderers prefrontal love not working properly - prefrontal lobe regulates emotions from amygdala
What were the results for the corpus callosum? (subcortical region)
Murderers had lower glucose metabolism than controls
What were the results for the amygdala? (subcortical region)
Murderers had reduced left + greater right amygdala activity compared to controls
What were the results for the thalamus? (subcortical region)
Murderers had greater right thalamic activity compared to controls
What were the results for the behavioural performance on CPT?
Groups didnt differ on any aspect
What couldnt Raine match the individuals on?
Wasnt possible to match them on handedness, head injury, or ethnicity
Couldnt match head injury, rest didnt have impact
What is the conclusion of this study?
- Findings cant demonstrate violence due to biology alone, social, physiological, cultural, + environmental factors have impact
- PET cant be used as diagnostic technique
- Overall, murderers pleading guilty by insanity have lower glucose metabolism than controls, so have different brain functioning to controls
