Chapter 19: Neuroimaging of Personality

The research focuses primarily on three of the "Big Five" traits—Extraversion, Neuroticism, and Agreeableness—which correspond to positive affect, negative affect, and social interaction, respectively. Studies investigating Extraversion demonstrated that this trait correlates with distinct neural responses to positive emotional stimuli, specifically finding that higher Extraversion scores are associated with greater activation of the amygdala in response to stimuli like happy faces or positive pictures. Research also established that activation in the anterior cingulate cortex (ACC) linked to positive words is consistently correlated with Extraversion, independent of the individual's current positive mood state. Conversely, Neuroticism is associated with processing negative emotional information. While ACC response to negative stimuli is moderated by negative mood state, suggesting an intra-individual "tuning" mechanism, Neuroticism is significantly linked to the temporal dynamics of brain activation. Specifically, highly neurotic individuals exhibit more sustained activation in the medial prefrontal cortex (MedPFC) when processing sad facial expressions, a finding consistent with this region's role in self-referential processing and potentially representing a vulnerability marker for later mood disorders, particularly related to the anxious facet of Neuroticism. Extending beyond these two traits, findings concerning Agreeableness suggest a positive correlation between this trait and activation in the right lateral prefrontal cortex (LPFC) during the processing of fearful faces, which may indicate the automatic engagement of neural mechanisms for regulating negative affect in agreeable individuals when faced with social conflict stimuli. Methodologically, researchers have advanced beyond the focus on single brain regions by employing functional connectivity analyses and developing the 'regions of variance' (ROV) approach as an empirical alternative to traditional 'regions of interest' (ROI) methods, maximizing the ability to identify trait-brain associations that exhibit high variability across subjects. Future advancements are expected to incorporate molecular genetics, investigating gene variations such as the serotonin transporter gene (5-HTTLPR) and epigenetic processes, to build more sophisticated biological models linking genetic predisposition, neural correlates, and personality traits.