Biological Classic Evidence Raine et al. WJEC AS/A2

Brain Abnormalities in murderers by PET

Early theories about criminal behaviour suggested might be physical difference in criminal and non-criminal enable us to identify individuals before commiting a crime.Lombroso; physical features that criminals typically had narrow, sloping forehead, prominent eye ridges, large ears & protruding chin.Brain Scanning opened new way to research differences in criminals and non-criminals. Might be specific areas of brain are different in criminals, may predispose individuals to violent behaviour.Animal research and studies of people w/ brain damage have found this.Raine et al. focused on particular group criminals = Individuals committing a murder & entered plea of not guilty by reason of insanity (NGRI).Proposed on basis of previous research, that seriously violent individuals: Have brain dysfunction in prefrontal cortex, angular gyrus, amygdala, hippocampus, thalamus and corpus callosum. Not have brain dysfunction in areas of brain that have been implicated in mental illnesses, not previously related to violence; caudate,putamen, globus pallidus, midbrain, cerebellum.

Methodology

Quasi-experiment with matched pairs design.IV: NGRI or not          DV: Brain differencesParticipants; Murderers 41 (39 men, 2 women), mean age 34.3 yrs. All charged w/ murder or manslaughter & ALL pleaded not guilty by reasons for insanity NGRI or incompetent to stand trial.Referred to University California, examination obtain proof diminished capacity.Pp's instructed be medicated free, checked by urine scan, two weeks prior brain scanning.Control Group matching each murderer w/ normal individual of same sex & age.6 Schizophrenic from mental hospital.Other controls NO history psychiatric illness, nor w/ close relatives & no significant physical illness. None taking medication.

Schizophrenia                                                       6History head injury or organic brain damage 23History psychoactive drug abuse                      3Affective Disorder                                                2Epilepsy                                                                 2History hyperactivity & learning disability       3Personality disorder                                            2

Procedures

Sample obtained using Opportunity Sampling. PET scan used to study active brain. ALL Pp's given injection of 'tracer' - FDG = Taken up by active areas of brain and possible compare brains of NGRI & Control Group. ALL Pp's asked to do continuous performance task - CPT = Aimed to activate target areas brain so could see different areas functioning.

Findings

Brain DifferencesFound reduced activity in brain NGRI Pp's areas previously linked to violence; prefrontal cortex, left angular gyrus, corpus callosum, left hemisphere only reduced activity in amygdala, thalamus and hippocampus.Found increased activity in brain of NGRI Pp's areas NOT previously linked to violence; cerebellum, right hemisphere increased activity in amygdala, thalamus and hippocampus. Reduced Activity; some areas, notably areas previously linked to violence. Abnormal Asymmetries; reduced activity on left side brain, greater activity on right. Applied some areas identified in hypothesis linked to violence (amygdala, thalamus & hippocampus) No Differences; many brain structures, associated w/ mental illness but not violence.

Performance on CPT = Both groups performed similarly, any observed brain differences not related to task performance.Other differences NOT controlled for; Handedness = 6 murderers left handed Ethnicity = 14 murderers Non-white, but showed no significant difference. Head Injury = 23 murderers history of head injury, didn't differ from murderers w/ no history of brain injury.

Conclusion

Animal & human studies have identified links between areas of brain and aggression.However neural processes underlying violence are complex and can't be reduced to single brain mechanism.Vioent behaviour probably best explained by disruption of network interaction between the brain mechanisms rather than single structure. Such disruption NOT cause violent behaviour but would predispose an individual to violent behaviourAmygdala; Associated w/ aggressive behaviour in animals and humans. The destruction of the amygdala in animals results in lack of fear = (Might explain) Fearlessness associated w/ violent activity.

Results NOT show violent behaviour is determined by biology alone; clearly social, psychological, cultural and situational factors play important roles in predisposition to violence. Results NOT show murderes pleading NGRI not responsible for actions, nor PET used as means of diagnosing violent individuals. NOT show brain dysfunction causes violence = even result brain dysfunction is an effect of violence. NOT show violence be explained results, results relate only to criminal behaviour. Findings DO suggest link between brain dysfunction and predisposition towards violence in specific group NGRI.