Set shifting and reversal learning in borderline personality disorder

Background: People with BPD have been shown in some studies to have structural deficits in regions of the prefrontal cortex. A sensitive test of prefrontal cortex function is the intra-dimensional/extra-dimensional (IDED) set shifting task. This study sought to examine whether people with BPD demonstrate impaired performances on extra-dimensional shift (EDS) and reversal learning aspects of this task similar to those seen in conditions such as schizophrenia and bipolar affective disorder. Method: Twenty subjects with BPD and 21 healthy control subjects were administered the IDED task from the Cambridge Neuropsychological Test Automated Battery cognitive test battery. EDS and reversal learning errors were compared between the groups using repeated measures ANOVAs. Results: There was no significant difference between the BPD and control participants in EDS or reversal learning on the IDED task or in stage of the task completed. There was a medium effect size difference (Cohen's d=0.4) for simple reversal learning and small effect sizes for reversal learning (Cohen' d=0.17) and IDED shift stages (Cohen's d=0.2 and -0.3 respectively). Conclusions: Participants with BPD in this study did not show statistically significant deficits in EDS or reversal learning, although small to medium effect sizes were found. These findings distinguish them from sufferers of schizophrenia and bipolar affective disorder and are in keeping with the idea that BPD is a distinct condition with discrete neuropathological processes.