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BackgroundIt has recently been suggested that auditory hallucinations are the result of a criterion shift when deciding whether or not a meaningful signal has emerged. The approach proposes that a liberal criterion may result in increased false-positive identifications, without additional perceptual deficit. To test this hypothesis, we devised a speech discrimination task and used signal detection theory (SDT) to investigate the underlying cognitive mechanisms.MethodSchizophrenia patients with and without auditory hallucinations and a healthy control group completed a speech discrimination task. They had to decide whether a particular spoken word was identical to a previously presented speech stimulus, embedded in noise. SDT was used on the accuracy data to calculate a measure of perceptual sensitivity (Az) and a measure of response bias (β). Thresholds for the perception of simple tones were determined.ResultsCompared to healthy controls, perceptual thresholds were higher and perceptual sensitivity in the speech task was lower in both patient groups. However, hallucinating patients showed increased sensitivity to speech stimuli compared to non-hallucinating patients. In addition, we found some evidence of a positive response bias in hallucinating patients, indicating a tendency to readily accept that a certain stimulus had been presented.ConclusionsWithin the context of schizophrenia, patients with auditory hallucinations show enhanced sensitivity to speech stimuli, combined with a liberal criterion for deciding that a perceived event is an actual stimulus.

AimsIn the present study, our aim was to investigate the oxidative-antioxidative systems in unmedicated first-episode psychosis (FEP) patients at the beginning and after short-term treatment. MethodsThis study consisted of 29 patients who experienced an FEP and 25 control subjects. In order to investigate the oxidative status, we determined plasma malondialdehyde (MDA) levels, oxidizability of red blood cells, oxidation and oxidizability of apolipoprotein B-containing lipoproteins (apo B-basal MDA and apo B-MDA). In order to evaluate the antioxidative defense, we measured serum total antioxidative capacity, uric acid, albumin, total bilirubin and vitamin E levels and serum paraoxonase/arylesterase, whole blood glutathione peroxidase (GPx) and red blood cell superoxide dismutase activities before and after 6 weeks of treatment in patients with FEP. ResultsPlasma MDA and apo B-basal MDA levels and red blood cell superoxide dismutase activity were significantly higher and serum arylesterase and whole blood-GPx activities were lower in the FEP group than those of the healthy control group. There were not any significant changes in the oxidative and antioxidative system parameters (except increased vitamin E levels) after treatment. ConclusionsThe results of this study suggest that FEP is accompanied by oxidative stress. However, further studies are needed to clarify the role of oxidative stress in the physiopathologic mechanisms of FEP, so that oxidative and antioxidative system parameters can be used in the management of these patients. In accordance with psychiatric evaluation, for a better management, patients with FEP may require a multidisciplinary approach, including oxidative and antioxidative system parameters.