Working memory constrains abstraction in schizophrenia

Background: Abstraction has long been considered an area of differential co gnitive deficit in schizophrenia, primarily because of patients' poor perfo rmance on the Wisconsin Card Sorting Test (WCST), Yet, the complexity and m ultidimensional nature of the WCST increases the likelihood that several di fferent cognitive processes, perhaps mediated by different neural systems, are being tapped. Methods: In the current study, the Abstraction and Working Memory (AIM) tas k was designed to disentangle abstraction and working memory so that the ef fects of each cognitive domain could be independently analyzed. The AIM tas k and a battery of neuropsychological tests were administered to 62 patient s with schizophrenia and 62 matched healthy volunteers. Results: Whereas patients with schizophrenia demonstrated deficits in simpl e abstraction, they were disproportionately impaired with the addition of a minimal memory requirement. Conclusions: Group differences on WCST performance appear to be attributabl e to patients' inability to maintain information over a short delay, before that information is used for more complex cognitive operations. (C) 1999 S ociety of Biological Psychiatry.