Download Brain abnormalities in murders indicated by positron emission

Brain abnormalities in murders
indicated by positron emission
tomography (PET)
Raine et al.
Background Information
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Previous research has indicated that
dysfunction in certain localized brain areas
may predispose individuals to violent
behavior.
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Prefrontal cortex
Corpus callosum
Amygdala
Hippocampus
Techniques of brain scanning
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PET scans- relationship between the
metabolic activity in the brain and mental
processes.
Small amount of radioactive material ->
bonds to glucose (tracer) -> glucose used as
energy -> areas which are most active
absorb it -> produces colored images of the
level of activity.
Others: MRI (changes of oxygen levels) and
MEG (nerve networks)
AIM of Study
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Using Pet Scans
Monitoring changes in cortical and sub
cortical brain functioning
(NGRI) Murders who have pleaded not guilty
by reason of insanity will show brain
dysfunction in their prefrontal cortex as well
as in other areas that are linked to violent
behavior.
Method
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Laboratory experiment
Independent measures design (between-subjects)
Quasi or (natural experiment)
Paired match design
Independent variable: murder or not
Dependent: Results of the PET scans.
Exp. Group- 41 subjects (39 males and 2 females) referred to the
imaging centre for legal reason.
Con. group- 41 non murders paired on the basis of age and sex.
Screened for their mental and physical health.
Everyone was medication free for two weeks prior to the experiment.
Everyone was injected with glucose tracer
Work on a continuous performance task –detect target signals for 32
minutes
Compared
Areas that were analyzed
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Look on study =]
Results
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Less activity in their
prefrontal and parietal
areas
More activity in their
occipital areas
No difference in their
temporal areas.
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Less activity in corpus
callosum
Imbalance of activity in
amygdala and
hippocampus (more
on right)
Imbalance in the
thalamus (more on right
but no difference on
left)
Explanations
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Amaygdala: usual
emotional responses
such as a lack of fear.
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Corpus Callosum:
inappropriate emotional
expression and an
inablity to grasp longterm implications of a
situation.
Strengths
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Control (some)
PET scans
Possibility of drug treatments- but this might
carry some ethical dilemmas.
Weaknesses
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PET scans are still being developed
The task (bearing no violent acts)
No cause and effect can be made.
Not all murders are committed in a violent
manner. Ex. Poison.
Reductionism- physiological
Other factors that are not considered: social
background, learned responses, ect.