Input dysfunction and beyond--an evaluation of CPT components

The aim of our project is to analyze the functional meaning of neurocognitive components of the Continuous Performance Tests (CPT), which may be responsible for the well-documented performance deficit. Since the CPT can be considered as a vulnerability marker for schizophrenia, this question is of special interest. We set up a test battery testing five different cognitive processing modes: perceptual organization, selective attention, short-term memory (storing component), working memory (rehearsal component), and vigilance/sustained attention. In order to avoid the pitfall of interpreting results confounded by psychometric differences within tasks, we created psychometrically parallel versions within each experimental block (following the proposals of Chapman and Chapman [J. Nerv. Ment. Dis. 171 (1983) 658]). At the main experimental session, we tested newly admitted patients with a DSM diagnosis of schizophrenia during remission (N=30), patients with major depressive disorder (MD) (N=18), and healthy controls (N=20). Results showed that differences specific for schizophrenia are seen at the experimental block, which tests perceptual organization. However, all levels of perceptual organization performance were concerned, i.e., from processing organized to non-organized patterns. The regression analysis showed that 3-7 CPT version performances could be explained by problems with short-term memory, sustained attention, and perceptual organization. In light of these findings, we discussed whether etiology of schizophrenia could be conceptualized as a circumscribed neurocognitive deficit or a multifunctional, multilocal deficit.