Calibration and cross-validation of MCCB and CogState in schizophrenia.

RATIONALE: Cognitive impairment associated with schizophrenia is a key predictor of functional outcomes. The FDA-accepted MATRICS Consensus Cognitive Battery (MCCB) is held to be the gold standard measure but there are concerns about its ease of administration, reliance on language causing problems with translation and possible practice effects. The CogState Schizophrenia Battery (SB) is suggested as a non-language-based alternative but there is no substantial, independent comparison. OBJECTIVES: The objective of this study was to assess the reliability and validity of these two assessment batteries. METHODS: One hundred forty-three participants with DSM-IV schizophrenia and schizoaffective disorder were recruited into three similar studies. Each study administered MCCB and SB tests on consecutive days (baseline 1 and 2) and follow-up 3-4 weeks later. RESULTS: Batteries' test-retest reliability was similar: SB composites correlated r = 0.66-0.78 between baselines, MCCB domains r = 0.69-0.90. Baseline 2 and follow-up SB composites correlated r = 0.65-0.80 and MCCB domains r = 0.62-0.87. MCCB tasks' practice effects (Glass' ∆ = 0.02-0.46) exceeded SB's (Glass' ∆ = 0.02-0.34). While the batteries' total scores correlated strongly (r = 0.79-0.82), apparently equivalent cognitive domains on each battery (e.g. psychomotor-attention) correlated r = 0.22-0.60, indicating substantial differences between some supposed counterparts. CONCLUSIONS: Clinical trials using either battery would benefit from initial practice sessions to ameliorate practice effects but the SB may be more suitable to measure change in the absence of repeated baselines. The MCCB domains' better correlations with social skills performance suggest that it may have an advantage for measuring cognition in relation to functional outcome.

Performance on a probabilistic inference task in healthy subjects receiving ketamine compared with patients with schizophrenia.

Evidence suggests that some aspects of schizophrenia can be induced in healthy volunteers through acute administration of the non-competitive NMDA-receptor antagonist, ketamine. In probabilistic inference tasks, patients with schizophrenia have been shown to 'jump to conclusions' (JTC) when asked to make a decision. We aimed to test whether healthy participants receiving ketamine would adopt a JTC response pattern resembling that of patients. The paradigmatic task used to investigate JTC has been the 'urn' task, where participants are shown a sequence of beads drawn from one of two 'urns', each containing coloured beads in different proportions. Participants make a decision when they think they know the urn from which beads are being drawn. We compared performance on the urn task between controls receiving acute ketamine or placebo with that of patients with schizophrenia and another group of controls matched to the patient group. Patients were shown to exhibit a JTC response pattern relative to their matched controls, whereas JTC was not evident in controls receiving ketamine relative to placebo. Ketamine does not appear to promote JTC in healthy controls, suggesting that ketamine does not affect probabilistic inferences.