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

对一个模棱两可的人物的感知是不稳定的，并且在可能的解释之间交替。微小的图形变化可以消除模糊刺激的歧义并稳定其感知。最近，我们发现了两个突出的事件相关电位，即前额-中央P200和侧边-中心P400，它们具有以下特征：(1)它们的振幅随着刺激模糊性的降低而单调增加；(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。我们在以下模型中解释这些成分：我们的感知系统将不完整和模糊的感觉输入与感知记忆内容相匹配，以构建稳定可靠的感知。一个高级概率（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。本提案的目标有两个轨道：在基础研究轨道中，我们的目标是研究：(1)P200/P400在感觉模式（视觉，听觉，体感）中的双重性效应的概括，(2)P200和P400之间的功能差异，以及(3)它们的空间来源。这条轨道的结果将有助于我们进一步了解在高级认知水平上感知可靠性的神经过程，整合各种感觉模式。在临床研究方面，我们主要关注亚斯伯格自闭症患者（AA）。AA参与者更多地依赖感官信息，而较少依赖知觉记忆。根据我们的模型，我们预测它们的P200/P400振幅与控制不同，有更陡的增长和更低的最大值。我们的目标是研究AA参与者与匹配对照组之间的差异：(1)一个新的行为标记（滞后距离）来量化之前的感知历史对当前感知的影响；(2)滞后距离与P200/P400效应大小的关系；(3)隐藏图形的P200/P400振幅模式，其感知主要取决于感知记忆内容的可用性。虽然AA的知觉症状最近在诊断中越来越重要，但其潜在机制仍然知之甚少。本研究结果将有助于厘清AA参与者知觉消歧的具体特征。此外，AA的生理标记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中进行统计，因此是这样一个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.