The function and structure of the brain has long been implicated in the explanation of violent behaviour. From cases studies as early as 1848, in which head injuries resulted in changes of personality and behaviour. The prefrontal cortex was identified as a region of interest as specific head wounds to this area resulted in increased aggression and violence. The improvement of neuropsychological testing and brain imaging has further described the role the prefrontal cortex plays.
Current theory and research indicates that the amygdalo-hippocampal complex (AHC) is implicated in the control of aggression and that the prefrontal cortex regulates and inhibits these emotions. There seems to be a substantial amount of evidence which supports the association between prefrontal cortex dysfunction and violent behaviour. A definition of violence is given by Brower and Price (2001), “Violence refers to actions that inflict physical harm in violation of social norms”. These conclusions can be arrived from the data of individuals who have suffered brain injury to the pre frontal cortex region.
Furthermore by studying subjects from forensic settings, such as those who have been categorized as having antisocial and violent tendencies and examining the function of the prefrontal cortex. This essay will look at the methodological problems of such research when examining the relationship between prefrontal cortex dysfunction and violent behaviour. The essay will also examine specific regions of the prefrontal cortex and there function and thus the implications this has on violence.
The essay will also examine the use of the term violence both by definition and measurement and highlight other effects prefrontal cortex dysfunction has on behaviour. Also other risk factors such as child abuse and interactions between biological predisposition and adverse environmental factors will be examined as histories of abuse are common in offender samples. According to Carlson (1995) Impulsive violence is a consequence of faulty emotional regulation. The prefrontal cortex is responsible for decision making, long term planning and moderating correct social behaviour.
It is located in the anterior part of the frontal lobe and is made up of “grey matter” The amygdale has the primary role of processing information such as emotional reactions; it provokes anger and violent emotional reactions to stimuli in the environment. It is located in the medial temporal lobe and is connected to the hypothalamus which in turn activates the sympathetic nervous system. It is also connected to the prefrontal cortex and this plays an important role in suppressing such behaviour.
Studies highlight that both increased activation of the amygdale and/or the decreased activation of the prefrontal cortex leads to violence and aggressive behaviour being displayed. Studies of brain injuries in specific locations and there affects on behaviour seem to support the association between the prefrontal cortex and violence. One of the earliest cases documented is that of Phineas Gage, a railroad worker who had an iron rod pierced his skull in 1848. This was the first time it was suggested that specific brain regions affect personality and behavior.
It is reported that Gage’s left frontal lobe was severely damaged and this lead him to behave irresponsibly, childish and have outburst of temper (Damasio, Grabowski, Damasio 1994). As increasing numbers of case studies examined head injuries, specific injuries to the prefrontal cortex and frontal lobes was identified as causing aggressive and violent behaviour suggesting dysfunction of these areas had a significant role to play. Grafman (1996) compared self report information and family member’s questionnaires of Vietnam veterans who had suffered penetrating head wounds during service.
It was found that subjects with frontal lobe injury, specifically lesions in the ventromedial frontal cortex displayed significantly more violent and aggressive behaviour than subjects with injuries in different region of the brain. This was part of Grafman’s longitudinal “Vietnam Head Injury Study” (VHIS). Also Patients with medial frontal injury made self reports of increased violent and aggressive behaviour which was consistent with family member’s reports (Carrion, Chacartegui and Ramosz, 2003).
They also report veterans who suffered exclusively from orbitofrontal lesions where reported by family members to have higher levels of aggression and violence than the patients where subjectively aware of. As science and research techniques, have improved such as brain imaging, cognitive tests, neuropsychological tests and the classification of personality disorders. A greater understanding of the specific role the prefrontal cortex and its functioning plays can be made when comparing violent and non-violent groups.
In forensic samples, personality disorders were significantly associated with previous criminal convictions, and in the case of antisocial personality disorder there was a disproportional amount of violent convictions (coid 1999 cited in Carlson 2004). In regards to the pre frontal cortex Raine, Lencz, Bihrle, LaCasse and Colletti (2000) found an 11 % reduction in volume of grey matter in individuals with antisocial personality disorder. This would possibly support the association between pre frontal cortex functioning and antisocial behaviour but what of violence?
Amen, Stubblefield, Carmichael (1996) used functional imaging to measure the prefrontal cortex activity of adolescence and adults who had a history of physical attacks on other people and found that there was decreased activity when compared to a control group. I Another study by Raine, Meloy, Bihrle, Stoddard, LaCasse and Buchsbaum (1998) found when using Structural Magnetic Resonance Imaging decreased prefrontal activity and increased sub cortical activity in the brains of murderers.
This was not true however, for cold blooded murders who displayed apparently normal pre frontal lobe activity. This could suggest that the prefrontal dysfunction is greatly associated with more reactive aggression and violence and not planned instrumental controlled violence. Following this Raine (2002) concludes that neuro imaging studies suggest that in regards to serious antisocial and violent behaviour, the prefrontal cortex is implicated in its aetiology.
Also psychopathy is commonly associated with violence; these individuals commit more violence within institutions than any other offenders and have higher levels of recidivism for violent crimes (Hare and Hart 1993 cited in Carlson 2004). Psychopaths not only engage in reactive violence, but are significantly more likely to engage in instrumental violence compared to non psychopathic offender (Blair 2006). Also individuals with psychopathy who use excessive violence can present with orbital frontal lobe dysfunction (Blair, 2003; Kiehl, Smith, Hare, Mendrek, Forster, Brink and Liddle 2001).
Furthermore a study used EEG’s to measure prefrontal cortex activity in 333 prisoners who had been charged with a violent crime, specifically those with habitual physical aggression or explosive rages. It was found that 56. 9% of the prisoners had EEG abnormalities, 62. 2% of those had EEG abnormalities in the frontal cortex compared to 11. 8% of prisoners who had only committed one act of violence in a single episode (Williams 1969 cited in Brower and Rice 2001).
Another way to help understand prefrontal cortex function in regards to violent behaviour is to measure the neurochemical activity in the prefrontal cortex’s of violent and non-violent groups. This would again suggest that prefrontal cortex dysfunction is associated with violence; however exact knowledge of the role of the dysfunction when using such a research method is limited. Serotonin levels are functionally relevant throughout the brain, especially in the prefrontal cortex, leading to an effect on behaviour.
There are a large number of serotonergic axons in the prefrontal cortex and measuring the levels of serotonin, 5-hydroxytryptomine (5-HT) by measuring 5-hydroxyindoleacetic acid (5-HIAA) which is metabolite of serotonin, present in the Cerebrospinal Fluid (CSF) would indicate the role serotonin is involved with the function of the prefrontal cortex. It is found that Low levels of 5-HIAA are associated with aggression, and other forms of antisocial behaviour including assault, arson, murder and child battery (Lidberg et al, 1984, Virkkunnen, Dejong, Bartko, Goodwin and Linnoila 1989).
This would suggest that serotonin is crucial in the function of the prefrontal cortex and the regulation of emotional behaviour. However an alternative model in relation to serotonin and prefrontal cortex is proposed by Meyer et a (2007). They found that extracellular 5-HT levels in the prefrontal cortex are not decreased in groups with aggressive or violent tendencies. Instead using (F) Setoprone Positron Emission Tomography (PET) to measure 5-HT binding potential (BP). There was a linear decrease in 5-HT BP in relation to aggression.
This would make sense as there is an inverse relationship between extracellular 5-HT and 5-HT receptors in the prefrontal cortex. Both measures of EEG’s and neurochemical activity in the prefrontal cortex suggest that in violent offenders this brain region appears not to be functioning in the same way as non-violent controls. This would support the assumption that the prefrontal cortex modulates and inhibits aggressive, violent and emotional impulses of the amygdale and hippocampal complex.
Dysfunction of the frontal cortex indentified in these studies appears to at least correlate with violent tendencies. A measure of violence is a difficult measure to attain and this can lead to an under reporting of violent behaviour in the research. The majority of the studies use home office data, conviction rates, self report questionnaires and offenders who have been apprehended for their violence. According to Chappell (1995) definitions of violence are socially constructed and although, assault and sexual violence routinely reported, other social relationships are not examined with the same vigour.
It is found that using victim surveys and National Crime Statistics often bring different results especially for different types of crime such as sexual assault. Also unintentional actions such as accidental death are usually not counted in National crime statistics. This creates two possible problems, firstly that the samples of violent offenders could have displayed violent behaviour and have not been apprehended every time as it didn’t come to the authorities attention, so the violence in the group is under emphasized.
And secondly, violent offenders, when using self report questionnaires may “down play” and under report their own violent behaviour only referring to known offences. However Brower and Price (2001), conclude that there is only a casual relationship between prefrontal cortex dysfunction and violent behaviour. Aggression, especially impulsive aggression is associated more directly with prefrontal cortex dysfunction. Violence is difficult to define and measure and clinical studies seem to support the association with aggression.
Overall, a comprehensive review conducted by Kendal and Freed (1989) found that the evidence for the association between violent behaviour and frontal cortex dysfunction is weak at best. According to Anderson, Bechara, Damasio, Tranel and Damasio (1999), injuries to the medial frontal and orbital frontal cortex are associated with increased levels of reactive aggression. Also the orbital frontal cortex has been identified as playing a role in norm violation and prosocial behaviour (Berthoz, Armony, Blair and Dolan 2002, Hare 1991).
Furthermore injury to the orbitofrontal cortex impairs empathy, risk avoidance and social judgement and that could possibly inhibit inappropriate behaviour and reactive aggression (Virkkunen, Nuutila and Huusko, 1976 cited in Brower and Price 2001). Thus it appears the orbital frontal cortex is involved in two processes in regards to behaviour, 1) is that it asses reward and risk of behaviour and 2) it modulates social judgements and cognitions, norms and their violations (Rolls 2002).
Also some research supports the notion that the prefrontal cortex doesn’t inhibit but instead facilitates the amygdala with regards to reactive aggression. The prefrontal cortex both increases and decreases the probability of aggression due to the function of social cues present in the environment. King, Blair, Mitchell, Dolon and Burgess (2006), used scenarios on a computer where participants must either kill an attacking assailant or aid an injured passive human casualty in a game.
Functional Magnetic Resonance (FMRI) scans where taken of the brain during each task, and it was identified that there was a common circuit that is involved with both compassionate and violent behaviour. This circuit included the amygdala, and the ventromedial prefrontal cortex. This would seem to contradict previous findings based on a model where the prefrontal cortex inhibits aggressive and violent impulses and action. The prefrontal cortex is involved in such behaviours but its role may be more complicated than first thought.