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04-07-2013 | Mental health | Article

Tasks identify cognitive deficit targets in schizophrenia

Abstract

Free abstract

medwireNews: Researchers have identified three measures of neurocognitive impairment in patients with schizophrenia that stand up to repeated assessment, making them suitable for intervention studies.

The three measures - Dot Probe Expectancy (DPX) and AX continuous performance task (AX-CPT), Relational and Item-Specific Encoding and Retrieval (RiSE) task, and Jittered Orientation Visual Integration (JOVI) task - form part of the four constructs of the Cognitive Neuroscience Test Reliability and Clinical applications for Schizophrenia (CNTRaCS) consortium and measure goal maintenance, episodic memory, and visual integration, respectively.

The fourth construct, the Contrast-Contrast Effect (CCE) task, which measures perceptual gain control, showed no association with schizophrenia.

In all, 99 outpatients with schizophrenia and 131 mentally healthy controls participated in the study and completed the five tests at two sessions spaced 7 days apart and a third session 14 days later.

Milton Strauss (University of New Mexico, Albuquerque, USA) and colleagues found patients scored significantly higher than controls on all the tasks except for the CCE task, for which there was no difference.

The DPX, AX-CPT, RiSE, and JOVI tasks also showed good test-retest reliability, demonstrating suitability for measuring treatment effects over time.

The DPX and AX-CPT showed the greatest reliability and either would be "good choices for treatment studies wishing to assess specific changes in cognitive control and goal maintenance," say the researchers in Schizophrenia Bulletin.

JOVI would be suitable for assessing the effects of treatment on visual integration, they add, but they found accuracy measures on this task were more reliable than threshold measures.

For RiSE, its strong validity means it "has excellent interpretability in terms of understanding mechanisms of pathology and potential mechanisms of change in a treatment study," comment Strauss et al. But researchers would need to weigh this against its somewhat lower reliability, they add.

The team notes, however, that practice effects were evident for the AX-CPT, DPX, and JOVI tasks, with performances improving over time in both groups, although the magnitude of group differences remained stable.

The practice effects were greatest between the first and second sessions. The researchers therefore suggest using multiple baselines to protect against such effects when using these measures in treatment studies.

This would involve removing the greatest practice effect from the evaluation, which in this case was from the first to the second session, and allow establishment of task performances from the second session as they are likely to remain stable at subsequent sessions, the researchers explain.

They also note an increase in practice effects on the DPX and AX-CPT with age.

"Important recommendations for treatment studies are therefore for the inclusion of younger patients to minimize practice effects and for baseline assessments prior to intervention," they write.

medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Lucy Piper, Senior medwireNews Reporter

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