Perceptual inference depends on an optimal integration of current sensory evidence with prior beliefs about the environment. Alterations of this process have been related to the emergence of positive symptoms in schizophrenia. However, it has remained unclear whether delusions and hallucinations arise from an increased or decreased weighting of prior beliefs relative to sensory evidence. To investigate the relation of this prior-to-likelihood ratio to positive symptoms in schizophrenia, we devised a novel experimental paradigm which gradually manipulates perceptually ambiguous visual stimuli by disambiguating stimulus information. As a proxy for likelihood precision, we assessed the sensitivity of individual participants to sensory evidence. As a surrogate for the precision of prior beliefs in perceptual stability, we measured phase duration in ambiguity. Relative to healthy controls, patients with schizophrenia showed a stronger increment in congruent perceptual states for increasing levels of disambiguating stimulus evidence. Sensitivity to sensory evidence correlated positively with the individual patients’ severity of perceptual anomalies and hallucinations. Moreover, the severity of such experiences correlated negatively with phase duration. Our results indicate that perceptual anomalies and hallucinations are associated with a shift of perceptual inference toward sensory evidence and away from prior beliefs. This reduced prior-to-likelihood ratio in sensory processing may contribute to the phenomenon of aberrant salience, which has been suggested to give rise to the false inferences underlying psychotic experiences.

中文翻译：

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精神分裂症的精神病经历和对感官证据的敏感性。

感知推理取决于当前感官证据与先前对环境的信念的最佳整合。这一过程的改变与精神分裂症阳性症状的出现有关。然而，目前尚不清楚妄想和幻觉是否是由于先前信念相对于感官证据的权重增加或减少而引起的。为了研究先验似然比与精神分裂症阳性症状的关系，我们设计了一种新的实验范式，通过消除刺激信息的歧义来逐渐操纵感知上模糊的视觉刺激。作为可能性精度的代表，我们评估了个体参与者对感官证据的敏感性。作为感知稳定性先验信念精度的替代品，我们测量了模糊性的阶段持续时间。相对于健康对照组，精神分裂症患者在一致知觉状态方面表现出更强的增量，以提高消除歧义的刺激证据的水平。对感官证据的敏感性与个体患者感知异常和幻觉的严重程度呈正相关。此外，此类经历的严重程度与阶段持续时间呈负相关。我们的结果表明，知觉异常和幻觉与知觉推理转向感官证据并远离先前信念有关。感觉处理中先验似然比的降低可能会导致异常显着性现象，这被认为会引起精神病体验背后的错误推论。