The role of the prefrontal cortex in the expression of impulsive- and premeditated- aggression
Haberle, SK (2011) The role of the prefrontal cortex in the expression of impulsive- and premeditated- aggression. PhD thesis, University of Tasmania.
The notion that there is a relationship between frontal lobe damage and
aggressive behaviour has been recognised in the clinical literature for over 50 years.
However, although there is evidence for an association between general brain
dysfunction and aggression, there is little evidence pertaining to subclinical
impairment and the propensity for aggressive behaviour. Further to this, given the
functionally heterogeneity of the prefrontal cortex, it is vital to delineate the specific
roles of the dorsolateral, orbitofrontal and medial aspects of the prefrontal cortex in
the expression of aggression.
Two forms of aggression are distinguished: reactive, impulsive-aggression
and goal-directed premeditated aggression. While impulsive-aggression is typically
described as an emotionally-charged aggressive response characterised by a lack of
control, premeditated aggression is considered to be a planned and controlled
aggressive display that is instrumental in nature. The qualitative differences between
these subtypes of aggression suggest distinct neuropsychological differences
mediating the likelihood of their display.
The aim of this thesis was to clarify the role of the prefrontal cortex in
subclinical impulsive-aggression and premeditated aggression. More specifically,
possible executive functioning deficits mediated by the dorsolateral prefrontal cortex,
and emotion recognition, impulsivity, and response reversal capabilities mediated by
the orbitofrontal cortex were explored. Participants included university
undergraduate students identified as having high levels of trait aggression, classified
as either predominantly impulsive, or predominantly premeditated in nature.
Experiment 1 (n=85) explored possible executive deficits using a battery of neuropsychological measures pertaining to dorsolateral functioning. It was found that
impulsive-aggressive individuals performed significantly poorer on measures of
cognitive flexibility, planning, problem-solving, and flexibility of verbal thought
Experiment 2 (n=87) sought to identify possible deficits in interpretations of
facial expressions of emotion and hostile attribution biases. Contrary to expectations,
the results indicated that while impulsive- and premeditated-aggressive individuals
do not incorrectly interpret emotional expressions, premeditated-aggressive
individuals attributed greater levels of aggression to neutral faces.
Experiment 3 (n=87) investigated functions of the orbitofrontal cortex,
namely impulsivity, response reversal, and decision-making capabilities. No
differences between impulsive-aggressive and premeditated-aggressive individuals
were found on any of these measures suggesting negligible involvement of the
orbitofrontal cortex in subclinical aggression.
Overall, the results from this thesis suggest distinct neuropsychological
processes in individuals who display predominantly impulsive-aggressive behaviour
compared to those who display predominantly premeditated-aggression. While
impulsive-aggression may result from executive dysfunction pertaining to the
dorsolateral region of the prefrontal cortex, the display of premeditated aggression is
related to functioning of the orbitofrontal cortex mediating the interpretation of
aggression in others. Such findings have important implications not only in the
understanding of the causal features of such behaviour, but also in the development
and implementation of successful treatment strategies.
|Item Type:||Thesis (PhD)|
|Additional Information:||Copyright the Author|
|Keywords:||aggression,, executive functioning, frontal lobes, emotion recognition|
|Deposited By:||ePrints Officer|
|Deposited On:||08 Dec 2011 12:28|
|Last Modified:||18 Apr 2012 11:17|
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