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The dot pattern expectancy (DPX) task was created to efficiently assess context-processing deficits in patients with schizophrenia. Three studies investigated the characteristics of the DPX relevant for clinical applications. To answer questions regarding the psychometric properties of the task, performance on this task was studied in 2 healthy samples. Acceptable reliability and internal consistency and retest reliability were found for most measures of context processing, but not for a difficulty control condition. These characteristics were also found in a suggested brief version (DPX[subscript brf]), which may be more practical for clinical purposes. In a 3rd study, schizophrenia patients showed a specific deficit in context processing, replicating previous findings. Findings of these studies indicated some promise for use of this task in measuring context processing and also identified characteristics of this task that need to be strengthened to increase reliability, feasibility, and single-subject interpretability. (Contains 4 tables and 3 figures.)

The functional neuroanatomy of tasks that recruit different forms of response selection and inhibition has to our knowledge, never been directly addressed in a single fMRI study using similar stimulus-response paradigms where differences between scanning time and sequence, stimuli, and experimenter instructions were minimized. Twelve right-handed participants were scanned on two standard cognitive control tasks, a stimulus-response incompatibility task, and a response inhibition task. A compound trial design allowed comparison of preparing to inhibit an upcoming automatic response to wholly inhibiting an automatic response. Furthermore, inhibiting an automatic response to perform an alternative task-relevant response was compared to wholly inhibiting an automatic response. No differences were found in prefrontal activity when preparing to inhibit an automatic response was compared to wholly inhibiting an automatic response, suggesting a mostly common network. The left inferior frontal gyrus was found to be commonly recruited during both tasks when controlled responses were required, likely due to its role in response selection. In contrast, the right inferior frontal gyrus was found to be more involved when task demands were stronger for response inhibition. Our results are largely consistent with models of cognitive control that postulate that separate psychological constructs, such as response selection and inhibition, are related processes largely served by a common prefrontal network. This prefrontal network is recruited to a greater or lesser extent depending on specific task demands. (Contains 5 figures and 5 tables.)

Demonstrating a specific cognitive deficit usually involves comparing patients' performance on 2 or more tests, The psychometric confound occurs if the psychometric properties of these tests lead patients to show greater cognitive deficits in 1 domain. One way to avoid the psychometric confound is to use tests with a similar level of discriminating power, which is a test's ability to index true individual differences in classic psychometric theory. One suggested way to measure discriminating power is to calculate true score variance (L. J. Chapman & J. P. Chapman, 1978). Despite the centrality of these formulations, there is no systematic examination of the relationship between the observable property of true score variance and the latent property of discriminating power. The authors simulated administrations of free response tests and forced choice tests by creating different replicable ability scores for 2 groups, across a wide range of various psychometric properties (i.e., difficulty, reliability, observed variance, and number of items), and computing an ideal index of discriminating power. Simulation results indicated that true score variance had only limited ability to predict discriminating power (explained about 10% of variance in replicable ability scores). Furthermore, the ability varied across tests with wide ranges of psychometric variables, such as difficulty, observed variance, reliability, and number of items. Discriminating power depends on a complicated interaction of psychometric properties that is not well estimated solely by a test's true score variance. Keywords: differential deficit, generalized deficit, psychometric confound, discriminating power, simu- lation study DOI: 10.1037/a0018400

The role of catechol-O-methyltransferase (COMT) va1158met in prefrontal cortical deficits associated with the liability to schizophrenia remains controversial. This study evaluated 464 healthy adult participants using three measures of executive functions in working memory: a 3-back version of the N-back continuous performance task (CPT) and two variants of the AX-CPT. The interpretability of N-back performance was confounded by possible generalized deficits, whereas the AX variants included internal controls for uncovering specific deficits. There was no relationship between the COMT genotype and N-back performance, whereas val/val individuals had a specific deficit on a dot-pattern version of the AX-CPT. In this case, a specific executive function known as context processing appeared to be compromised. These data suggest that the interpretability gained by including task manipulations to uncover specific deficits can enhance associations between cognitive and genetic levels of analysis. Keywords: schizophrenia, COMT, working memory, context processing, psychometric confound

Context processing is conceptualized as an executive function involved in voluntary, complex actions such as overcoming automatic responses. The present study tested the hypothesis that context-processing deficits in patients with schizophrenia are associated with a dysfunction of left dorsolateral prefrontal cortex (DLPFC). Using event-related functional magnetic resonance imaging (fMRI), 17 controls and 17 medicated patients performed a version of the AX task in which a learned, automatic response had to be inhibited. In controls, left DLPFC activity increased when preparing to overcome an automatic response, whereas patients with schizophrenia showed no differential activation. In controls, context processing appeared to be associated with the differential representation of cues associated with the need to provide top--down support for overcoming automatic responses. This mechanism appeared to be impaired in patients with schizophrenia.

Previous research on schizophrenia suggests that context-processing disturbances are one of the core cognitive deficits present in schizophrenia. However, it is not clear whether such deficits are specific to schizophrenia as compared with other psychotic disorders. To address this question, the authors administered a version of the AX Continuous Performance Test designed to assess context processing in a sample of healthy controls, patients with schizophrenia, and patients with other psychotic disorders. Participants were tested at index (when medication naive and experiencing their first contact with psychiatric services) and 4 weeks later, following medication treatment. At index, patients with schizophrenia and the psychotic comparison group demonstrated similar impairments in context processing. However, context-processing deficits improved in the psychotic comparison group at 4 weeks but did not improve in patients with schizophrenia.