Cortical and Subcortical Cognitive Deficits in Schizophrenia: Convergence of Classifications Based on Language and Memory Skill Areas

Abstract

Cortical and subcortical dementias have been reported to have distinct neuropsychological profiles. Previous studies of patients with schizophrenia have examined the memory-based profiles associated cortical and subcortical dementias. Although these two types of dementias have both language and memory-based profiles, the current study is the first to examine the overlap in classification associated with memory based and language based classifications. In this study, elderly (age >64 years) patients with schizophrenia (n=239) who varied in their lifetime outcome from chronic institutional care to stable community residence were tested with a neuropsychological battery that examined language and memory performance. Using a large sample of normal controls previously tested with this same assessment, normative standards for performance were developed. Schizophrenic patients were divided into cortical versus subcortical versus unimpaired groups on the basis of language and memory performance. Classification overlap ranged from a high of 30% (cortical profile) to a low of 14% (unimpaired profile). Furthermore, patients classified on the basis of verbal and memory ability areas did not differ in their performance in measures from the other ability areas. Data from a 1-year follow-up of part of the sample (n=147) suggested poor stability of the subcortical classification in particular. These data suggest that cortical versus subcortical profiles of cognitive performance in schizophrenia are inconsistent across ability areas, and are not likely to be the result of stable structural or functional brain deficits.