Neural processing of sensory ambiguity in healthy subjects and patients with Asperger Autism

对一个模糊图形的感知是不稳定的，并在可能的解释之间交替。微小的图形变化可以消除模糊的刺激，并稳定其感知。最近，我们发现了两个突出的事件相关电位，额中央P200和顶中央P400具有以下特征：（1）它们的幅度随着刺激模糊性的减少而单调增加;（2）它们的时间和空间分布在非常不同的视觉维度（几何，语义和运动）上高度相似。我们在以下模型的背景下解释这些组件：我们的感知系统将不完整和模糊的感官输入与感知记忆内容相匹配，以构建稳定和可靠的感知。高级概率（贝叶斯）推理单元计算感知结构的可靠性，结果反映在P200和P400振幅中。本项目的目标有两个方面：在基础研究方面，我们的目标是研究：（1）P200/P400模糊效应在感觉模态（视觉、听觉、体感）中的泛化，（2）P200和P400之间的功能差异，以及（3）它们的空间来源。这条赛道的结果将有助于我们进一步了解高级认知水平下感知可靠性的神经过程，整合各种感觉模态。在临床研究赛道中，我们专注于自闭症（AA）参与者。AA参与者更多地依赖感觉信息，较少地依赖知觉记忆。基于我们的模型，我们预测，他们的P200/P400振幅与对照组不同，具有更陡的增加和更低的最大值。我们的目标是研究AA参与者和匹配对照之间的差异，使用：（1）新的行为标记（2）滞后距离与P200/P400效应大小之间的关系;（3）具有隐藏图形的P200/P400幅度模式，其感知主要依赖于感知记忆内容的可用性。虽然AA的感知症状最近在诊断中获得了重要性，但其潜在机制仍然知之甚少。本研究的结果将有助于阐明认知消歧的具体特征。此外，AA的生理标志物到目前为止还很罕见。P200/P400效应的大效应量允许在单个参与者内进行统计，因此是这种标记的有希望的候选者。

The perception of an ambiguous figure is unstable and alternates between possible interpreta-tions. Tiny figural changes can disambiguate an ambiguous stimulus and stabilize its percept. Recently, we found two prominent event-related potentials, a fronto-central P200 and a pari-eto-central P400 with the following features: (1) their amplitudes increase monotonically with decreasing stimulus ambiguity and (2) their timing and spatial distributions are highly similar across very different visual dimensions (geometry, semantics and motion). We interpret these components in the context of the following model: Our perceptual system matches the incomplete and ambiguous sensory input with perceptual memory contents in order to construct stable and reliable percepts. A high-level probabilistic (Bayesian) inference unit calculates the reliability of the perceptual constructs, the result being reflected in the P200 and P400 amplitudes. The objective of this proposal has two tracks: In the Basic Research track we aim to study: (1) the generalisation of the P200/P400 ambi-guity effects across sensory modalities (visual, auditory, somatosensory), (2) the functional difference between P200 and P400, and (3) their spatial sources. The results from this track will help to further our understanding of the neural processes underlying perceptual reliability at an advanced cognitive level, integrated across sensory modalities.In the Clinical Research track we focus on participants with Asperger Autism (AA). AA par-ticipants rely more on sensory information and less on perceptual memory. Based on our model we predict that their P200/P400 amplitudes differ from controls, with steeper increases and lower maxima. We aim to study differences between AA participants and matched con-trols using: (1) a new behavioural marker (hysteresis distance) to quantify the influence of the preceding perceptual history on the current percept, (2) the relation between the hysteresis distance and the P200/P400 effect size and, (3) P200/P400 amplitude patterns with hidden figures, whose percepts depend mainly on the availability of perceptual memory contents. Although the perceptual symptoms of AA have recently gained importance in diagnostics, their underlying mechanisms are still poorly understood. The results form this track will help to clarify the specific feature of perceptual disambiguation in AA participants. Also, physio-logical markers of AA have been rare so far. The large effect sizes of the P200/P400 effects allow statistics within single participants and are thus promising candidates for such a marker.