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localization of function

specific areas of the brain are responsible for specific behaviours

Main study: Raine et al. (1997)


factors to consider when studying brain localization

- localization CANNOT explain all human behaviours: that would be reductionist
- it would minimize free will + impact of environment on behaviour
- complex behaviours (such as ‘murder’ with Raine et al, 1997) likely have complex causes
- brain exhibits neuroplasticity -- it re-wires itself by organizing new neural networks
- consequence of neuroplasticity: areas of the brain responsible for certain behaviours may change, so we must be CAUTIOUS when identifying those areas



positron emission tomography

- injects radioactive sugar that produces gamma rays while it's being metabolised by the brain
- relies on knowledge that parts of the brain will metabolise sugar at different rates
- depending on activity
- can show dynamic info but is less precise than fMRI
- some health concerns
- but overall quite safe


Raine et al. (1997) - Aim

To investigate brain abnormalities in murderers using PET scans


Raine et al. (1997) - Process

1. 41 prisoners charged with murder were paired with a control (non-murdering) subject
2. Each control subject had the same age, sex, and absence/presence of schizophrenia as their partner


Raine et al. (1997) - Findings

murderers exhibited:
- lower activity in the prefrontal cortex (linked to a loss of self-control and altered emotion)
- lower activity in the corpus callosum (connects the two brain hemispheres), suggesting less communication between the 2 hemispheres
- lower activity than with controls in the amygdala (linked to emotional expression)
- lower activity in the angular gyrus (linked with verbal ability and educational success)


Raine et al. (1997) - Conclusion

problems with the mentioned structures may cause a lack of inhibition for violent behaviour and greater fearlessness


Raine et al. (1997) - Evaluation

- gender imbalance (only 2 out of the 41 participants were female)
- matched-pairs design was a real strength as it ruled out other effects on brain activity
- but findings apply only to a sub-group of violent offenders (not to other types of violence or crime)
- some participants were murderers while others were manslaughterers (specific brain abnormalities should not be generalized)
- PET scan lacks precision -- exact brain locations are difficult to confirm


interpretation of the study

- findings don't necessarily mean that brain abnormalities in those regions cause violence; other social, psychological, and situational factors will be involved
- correlation does not imply causation, and even if there was causation in this case, the brain abnormalities may be an effect rather than a cause of behaviour
- findings don't necessarily mean that violence originates in these areas of the brain alone
- findings do not demonstrate the murderers are not responsible for their actions (free will!!), but they'd find it more difficult not to choose violence compared to those without the brain abnormalities
- the findings do not mean PET scans can diagnose
Conclusion: Raine et al (1997) is a thorough study which supports the idea that there is a link between brain abnormalities and violence


what to write when asked: "Explain one study related to localization of function"

- define localization of function
- outline + explain factors to consider when evaluating localization of function
- Raine et al, 1997: study on brain abnormalities in murderers
- define PET scan
- evaluate localization of function IN THE CONTEXT OF THE STUDY (by interpreting study results -- include background info/reasons for your opinions)

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