Indices of orbitofrontal and prefrontal function in Cluster B and Cluster C personality disorders

Abstract

Neuropsychological studies implicate disruption of frontal systems in personality disorders. Few studies have examined the performance of Cluster B and Cluster C personality disorder patients on tests of orbitofrontal (OFC) and prefrontal (PFC) cortex function. Patients carrying diagnoses of either Cluster B (n = 56) or Cluster C (n = 19) personality disorders were compared with healthy control subjects (n = 61) on the Iowa Gambling Task and University of Pennsylvania Smell Identification Test. They also completed the Wechsler Abbreviated Scale of Intelligence as a control for general intellectual ability. On the gambling task, Cluster B and Cluster C patients made more disadvantageous decisions during certain portions of the task but overall did not differ from healthy controls. Whereas no appreciable differences in olfactory identification performances were detected between patient and healthy control groups, IQ was higher for controls and was related to Cluster B patients' lower educational levels. Overall, there was limited evidence for neurocognitive inefficiency for personality disorder groups on tests sensitive to OFC and PFC function. The present study is among the first to report neurocognitive findings for the full range of Cluster B personality disorders and any Cluster C personality disorder.

Introduction

Personality disorders are severe psychiatric conditions characterized by long-standing and pervasive difficulties in two or more domains of function to include affect, cognition, impulse control, and interpersonal relations. Personality disorders affect between 9 and 15% of the United States population and they are associated with significant social, emotional, and physical disability (Grant et al., 2004, Lenzenweger et al., 2007). Whereas personality disorders are among the most chronic and financially burdensome of the psychiatric disorders (Comtois et al., 2003), relatively little is understood regarding their neurobiological bases.

Emerging evidence relates neuropsychological deficit to some personality disorders, namely borderline (Ruocco, 2005a), antisocial (Morgan and Lilienfeld, 2000), and schizotypal (Voglmaier et al., 1997). The nature of these deficits suggests a disruption of frontal-limbic systems, findings which converge with structural and functional neuroimaging studies of several Cluster B personality disorders (Ruocco, 2005b). Affected structures often include the prefrontal (PFC) and orbitofrontal (OFC) cortices, anterior cingulate, hippocampus, and amygdala (McCloskey et al., 2005). Diffuse and variable cognitive inefficiencies are typical of the neuropsychological profiles for the few personality disorders which have been examined, most notably borderline personality disorder (BPD). Neuropsychological deficits tend to be more pronounced on tests of executive function which involve planning abilities (e.g., Tower of London), as well as visual memory tests which may be additionally impacted by patients' poor organization skills (Ruocco, 2005a). Inefficiencies are also apparent in several other cognitive domains, including attention, working memory, verbal memory, cognitive flexibility, and visuospatial abilities, although findings are not consistent across studies. Whereas the bulk of the evidence links these deficits to frontal lobe dysfunction, far less attention has been paid to specific functions of the OFC and PFC as they relate to the personality disorders. In light of the role that these regions play in social cognition, affect regulation, and impulsivity, there is good reason to suspect involvement of these regions, especially the OFC, in personality disturbance (Berlin et al., 2005, Franken et al., 2008, Kringelbach and Rolls, 2004).

The present study is the first to our knowledge which examines the performance of both Cluster B (antisocial, borderline, histrionic, narcissistic) and Cluster C (avoidant, dependent, and obsessive–compulsive) personality disorders on neurocognitive measures of OFC and PFC function, contrasting the performances of these patient groups on tests of olfactory identification and decision-making (i.e., gambling) with healthy control participants. As a control for general cognitive ability, patients also completed brief intellectual assessment. We hypothesized that personality disorder patients would perform more poorly than healthy controls on tests of OFC and PFC functions, with the Cluster B group possibly demonstrating the greatest deficit. We are unaware of any neuropsychological studies of Cluster C patients; however, there is correlational evidence of an association between neuropsychological deficit and Cluster C personality traits in patients with closed head injury (Ruocco and Swirsky-Sacchetti, 2007). Thus, we hypothesized that Cluster C patients would perform at a level intermediate to that of Cluster B patients and healthy controls on the neurocognitive measures employed in the present study.