We began this chapter by noting advances in measurement and technology at the turn of the 21st century. Conceptual advances, too, are afoot. Both experimental psychologists and biological psychiatrists are turning from a strict focus on behavior and cognition to incorporate emotion. Spurred by comparative research, the idea of emotional operating systems in the brain offers fertile ground for generating hypotheses about mechanisms that might mediate connections between genes and traits (Panksepp, 1998).
Recurring basic emotional experiences may constitute key features of many of the traits common to both healthy personality and to personality disorders. For instance, in the rubric of the five-factor model of personality (see Table 5.2), fear might provide a core theme of neuroticism, playfulness of extraversion, and anger of disagreeableness. These connections can be verified not only psychometrically with measures designed to index emotional operating systems (Davis et al., in press) but also neurally with brain imaging methods that afford the necessary spatio-temporal resolution for visualizing the ongoing activity of emotional circuits (Canli et al., 2001; Knutson et al., 1999).
In the case of borderline and antisocial personality disorders, anger provides an especially relevant example. The chronic experience of anger constitutes a prominent feature of the personality traits neuroticism and disagreeableness. Accordingly, angry behavior may involve both negative emotion and lack of constraint. These phenomena may stem from a combination of hyperactivity in still vaguely defined threat processing regions of the subcortex (e.g., the amygdala and medial hypothalamus) and hypoac-tivity of inhibitory regions of the ventral prefrontal cortex (Davidson et al., 2000). Certainly, in both comparative and human research, frontal lobe damage can potentiate aggressive outbursts, while treatment with serotonergic agents, which enhances resting prefrontal metabolism, can diminish their frequency (Linnoila and Charney, 2000). In addition, peptides (e.g., substance P, vasopressin) and hormones (e.g., testosterone) may prime activity in subcortical circuits related to aggressive behavior in comparative models (Ferris et al., 1997; Siegel et al., 1999), and so may present promising pharmacotherapeutic targets for the future. An emotional systems perspective may thus inform both the diagnosis and treatment of personality disorders.
While applications of emotion theory may successfully generalize to the clinic, they may also inadvertently raise ethical issues (Farah, 2002). What if core features of personality disorders could be diagnosed with a brain scan? What if problematic behaviors could be selectively excised with pharmacological manipulations? At what point do people require treatment? Should effective treatments be administered to people who don't want to change? These emerging ethical questions underscore the continuing need for researchers and clinicians to work together toward a optimally combining of technological wisdom and human compassion in treating disorders of personality.
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