Pedrazzini Elena, Fellrath Julia, Thézé Raphaël, Ptak Radek
Laboratory of Cognitive Neurorehabilitation, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
Laboratory of Cognitive Neurorehabilitation, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Division of Neurorehabilitation, Geneva University Hospitals, Geneva, Switzerland.
Neuroscience. 2016 Nov 19;337:98-106. doi: 10.1016/j.neuroscience.2016.09.016. Epub 2016 Sep 17.
Illusory conjunctions (e.g. the confusion between the shape of one stimulus with the color of another stimulus) are the most dramatic expression of binding failures in vision. Under brief exposure or when attention is diverted illusory conjunctions may be observed in healthy participants, but they only represent a real-life problem for patients with parietal damage. However, it is unclear whether such failures reflect the impairment of early or late stages of visual processing. Here, we examined the time-course of visual processing using evoked potential measures in a patient with bilateral damage to the posterior parietal cortex presenting prominent binding failures. The patient was asked to identify colored letters that were briefly flashed to the left or right hemifield. When only one item was presented she adequately identified color or shape of left and right letters. In contrast, when presentation was bilateral she either identified the correct right shape-color combination and missed the item in the left hemifield (extinction) or combined incorrectly the right shape with the left color (illusory conjunction). Evoked potential analyses revealed a specific electrophysiological signature of illusory conjunctions, starting ∼105ms after stimulus onset over the right frontal cortex. These findings indicate that binding errors reflect failures of early stages of attentional filtering relying on the integrity of the posterior parietal cortex.
错觉性结合（例如将一个刺激的形状与另一个刺激的颜色混淆）是视觉中捆绑失败的最显著表现。在短暂曝光或注意力分散时，健康参与者可能会出现错觉性结合，但这对顶叶受损的患者来说才是现实生活中的问题。然而，尚不清楚这种失败是反映了视觉处理早期还是晚期阶段的损伤。在此，我们使用诱发电位测量方法，对一名双侧后顶叶皮质受损且存在明显捆绑失败的患者进行了视觉处理时间进程的研究。要求该患者识别短暂闪现在左半视野或右半视野的彩色字母。当只呈现一个项目时，她能够正确识别左右字母的颜色或形状。相比之下，当双侧呈现时，她要么正确识别了右侧形状 - 颜色组合而遗漏了左半视野的项目（消退），要么将右侧形状与左侧颜色错误组合（错觉性结合）。诱发电位分析揭示了错觉性结合的特定电生理特征，在刺激开始后约105毫秒出现在右侧额叶皮质。这些发现表明，捆绑错误反映了依赖后顶叶皮质完整性的早期注意力过滤阶段的失败。
