CLINICAL HANDBOOK OF SCHIZOPHRENIA

94 I. CORE SCIENCE AND BACKGROUND INFORMATIONPsycINFO database [accessed December 13, 2007] for published articles with the wordsschizophrenia or schizophrenic in the title, and WCST or Wisconsin Card in the title orabstract resulted in 392 citations in peer-reviewed journals, the earliest being ElizabethFey’s 1951 report demonstrating worse performance on the WCST among patients withschizophrenia relative to healthy controls. Two hundred and one such articles were publishedbetween January 1, 2001, and December 13, 2007. The sheer volume of ongoingschizophrenia research using the WCST speaks to the perceived importance of executivedeficits in patients with schizophrenia.At least when studied on a group level, the cognitive deficits in schizophrenia tend tobe diffuse/nonfocal (across a number of ability areas). However, it is interesting to notethat the findings in terms of executive dysfunction and initial acquisition of new informationare consistent with Kraepelin’s speculations regarding potential pathology in thefrontal and temporal lobes in schizophrenia. Although there is no identified, specificneuropathological cause associated with this disorder, the temporal and frontal regions,including the frontal–subcortical circuits, remain areas of intense research focus.Heterogeneity in virtually any conceivable dimension among patients with schizophreniais probably the single, most consistent attribute one can apply to the findingsfrom the larger schizophrenia literature in the past century. Attempts to divide schizophreniainto meaningful or homogenous subgroups date back to the earliest conceptualizationsof this disorder. Indeed, Bleuler spoke of this disorder as the schizophrenias.Modern diagnostic systems such as the fourth, text revised edition of the Diagnostic andStatistical Manual of Mental Disorders (DSM-IV-TR; American Psychiatric Association,2000) and the International Classification of Diseases (ICD-10; World Health Organization,1990) continue this tradition; the schizophrenia subtypes in these contemporary diagnosticsystems are largely based on patterns of psychopathological rather than cognitiveor functional symptoms. Seaton, Goldstein, and Allen (2001) estimated that there are over100 potential combinations of variables under three broad categories: causes of heterogeneity(age, education–socioeconomic status, comorbidity, etc.), heterogeneous characteristics (i.e.,neurological, cognitive, and symptom profile), and course and outcome of illness (stabilityor decline in symptoms, age of onset, etc.). Their own proposed model of heterogeneity inschizophrenia focused on cognitive aspects and was based on a four-cluster solution:(1) uniform mild-to-moderate impairment across domains; (2) similar pattern as that in(1), but with intact psychomotor skills; (3) impairment in shifting between reasoningstrategies, but intact abstraction skills; and (4) significantly impaired (dementia-like) performance.However, the authors listed numerous other cluster-analytic studies thatyielded cognitive subtypes of schizophrenia, but with widely different solutions based ondifferent patterns of cognitive performance. More recently, functional imaging techniqueshave also been applied to identification of homogenous subtypes. Unfortunately, consensuson the utility of any particular categorization scheme remains elusive.Trajectory of Cognitive Impairment in SchizophreniaPreonset Cognitive FunctioningThe contemporary model of schizophrenia is that of a neurodevelopmental condition.This view is not completely new. Kraepelin noted that some cases of schizophrenia maybe attributable to early brain insults. Barney Katz, in his 1939 doctoral dissertationfrom the University of Southern California, presented evidence that patients with psychosisexperienced a higher incidence of obstetrical complications at the time of theirbirth.