Brain abnormalities in murders indicated by positron emission tomography (PET) Raine et al.

Background Information Previous research has indicated that dysfunction in certain localized brain areas may predispose individuals to violent behavior. Prefrontal cortex Corpus callosum Amygdala Hippocampus

Techniques of brain scanning 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 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 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 Look on study =]

Results Less activity in their prefrontal and parietal areas More activity in their occipital areas No difference in their temporal areas. 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 Amaygdala: usual emotional responses such as a lack of fear. Corpus Callosum: inappropriate emotional expression and an inablity to grasp long- term implications of a situation.

Strengths Control (some) PET scans Possibility of drug treatments- but this might carry some ethical dilemmas.

Weaknesses 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.