Vercammen A, de Haan E H F, Aleman A
BCN NeuroImaging Center, University Medical Center Groningen, The Netherlands.
Psychol Med. 2008 Aug;38(8):1177-84. doi: 10.1017/S0033291707002437. Epub 2007 Dec 13.
It 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.
Schizophrenia 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 (beta). Thresholds for the perception of simple tones were determined.
Compared 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.
Within 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.
最近有人提出，幻听是在判断有意义的信号是否出现时标准发生变化的结果。该方法认为，宽松的标准可能会导致误报增加，而不存在额外的感知缺陷。为了验证这一假设，我们设计了一项言语辨别任务，并使用信号检测理论（SDT）来研究潜在的认知机制。
有幻听和无幻听的精神分裂症患者以及一个健康对照组完成了一项言语辨别任务。他们必须判断一个特定的口语单词是否与之前呈现的、嵌入噪声中的语音刺激相同。对准确性数据使用SDT来计算感知敏感性指标（Az）和反应偏差指标（β）。确定了简单音调感知的阈值。
与健康对照组相比，两个患者组的感知阈值更高，言语任务中的感知敏感性更低。然而，有幻听的患者与无幻听的患者相比，对语音刺激的敏感性更高。此外，我们发现了一些有幻听患者存在正向反应偏差的证据，表明他们倾向于轻易接受呈现了特定刺激。
在精神分裂症的背景下，有幻听的患者对语音刺激表现出更高的敏感性，同时在判断感知到的事件是实际刺激时采用宽松的标准。
