Reduced integrity of major white matter pathways has been discovered in people diagnosed with antisocial personality disorder (ASPD), according to a study recently published in Scientific Reports.
People with ASPD exhibit poor self-control, aggression and cold-heartedness. These personality traits mean that individuals with ASPD are more susceptible to criminal activity than the general population. In fact, it is thought that 47% of male prisoners are diagnosed with ASPD worldwide. ASPD is more common in men than women, with 3% and 1% diagnosed respectively in the population as a whole.
Research has suggested that ASPD is related to an underlying brain abnormality, although the exact pathophysiology remains unclear. However, structural impairments in white matter have been linked to impulsivity and risk-taking behaviour associated with ASPD.
In order to shed more light on white matter microstructure in ASPD, a team of scientists lead by Jiang Weixiong from Central South University, China recruited 20 participants diagnosed with ASPD and 23 healthy controls. The participants who were all male, completed tests for impulsivity and risk-taking behaviour before undergoing an MRI scan using diffusion tensor imaging which measured the diffusion of water molecules in the white matter.
The study revealed white matter deficits in ASPD patients. One particular area of interest was the right uncinate fasiculus which is a white matter tract that connects the limbic system to frontal brain regions. Part of the limbic system known as the amygdala is involved in producing emotional responses and certain areas in the frontal lobe act as the voice of reason which allows us to have control over our emotions most of the time. Therefore, structural deficits within the uncinate fasiculus could account for the behavioural disinhibition seen in ASPD patients.
The uncinate fasiculus also provides a connection between brain regions that control social and cognitive reasoning as well as decision making. Lack of connectivity between such areas are believed to underlie aspects of ASPD including poor moral judgement, lack of empathy and aggression. Additionally, deficits were observed in white matter pathways connecting the parietal and temporal networks which were correlated with impulsivity and risk-taking behaviour.
Overall, the study builds upon previous research that has revealed brain abnormalities in the white matter microstructure. These deficits, along with environmental factors could cause a “disconnection” that goes on to produce the socio-emotional deficits observed in ASPD patients. Understanding the structural pathophysiology of ASPD could have potential to uncover the neurological mechanisms that bring about the impulsivity, aggression and callous-mindedness associated with ASPD.