Pei Francesca, Baldassi Stefano, Procida Giuliano, Igliozzi Roberta, Tancredi Raffaella, Muratori Filippo, Cioni Giovanni
Associazione Italiana di Scienze della Visione, Cascina, Pisa, Italy.
Vision Res. 2009 Jul;49(16):2140-50. doi: 10.1016/j.visres.2009.06.006. Epub 2009 Jun 11.
In this study, we have used an electrophysiological paradigm to investigate the neural correlates of the visual integration of local signals across space to generate global percepts in a group of low functioning autistic kids. We have analyzed the amplitude of key harmonics of the Visual Evoked Potentials (VEPs) recorded while participants observed orientation-based texture and contour stimuli, forming coherent global patterns, alternating with visual patterns in which the same number of local elements were randomly oriented in order to loose any globally organized feature. Comparing the results of the clinical sample with those obtained in an age-matched control group, we have observed that in the texture conditions the 1st and 3rd harmonics, containing signature of global form processing (Norcia, Pei, Bonneh, Hou, Sampath, & Pettet, 2005), were present in the control group, while in the experimental group only the 1st harmonic was present. In the Contour condition the 1st harmonic was not present for both groups while the 3rd harmonic was significantly present in the control group but absent in the group with autism. Moreover, the amount of organization required to elicit significant 1st harmonic response in the texture condition was higher in the clinical group. The present results bring additional support to the idea that texture and contour processing are supported by independent mechanisms in normal vision. Autistic vision would thus be characterized by a preserved, perhaps weaker texture mechanism, possibly mediated by feedback interactions between visual areas, and by a disfunction of the mechanism supporting contour processing, possibly mediated by long-range intra-cortical connections. Within this framework, the residual ability to detect contours shown in psychophysical studies could be due to the contribution of the texture mechanism to contour processing.
在本研究中，我们运用了一种电生理范式，来探究一组低功能自闭症儿童中，局部信号跨空间进行视觉整合以生成整体感知的神经关联。我们分析了在参与者观察基于方向的纹理和轮廓刺激时记录的视觉诱发电位（VEP）关键谐波的幅度，这些刺激形成连贯的整体模式，与相同数量的局部元素随机定向从而失去任何全局组织特征的视觉模式交替出现。将临床样本的结果与在年龄匹配的对照组中获得的结果进行比较，我们观察到，在纹理条件下，包含全局形式处理特征（诺尔恰、裴、博内、侯、桑帕特和佩泰特，2005年）的第一和第三谐波在对照组中出现，而在实验组中仅出现第一谐波。在轮廓条件下，两组均未出现第一谐波，而第三谐波在对照组中显著出现，但在自闭症组中不存在。此外，在纹理条件下引发显著第一谐波反应所需的组织量在临床组中更高。目前的结果为正常视觉中纹理和轮廓处理由独立机制支持这一观点提供了更多支持。因此，自闭症患者的视觉特征可能是保留了，或许较弱的纹理机制，可能由视觉区域之间的反馈相互作用介导，以及支持轮廓处理的机制功能失调，可能由长距离皮质内连接介导。在此框架内，心理物理学研究中显示的检测轮廓的残留能力可能归因于纹理机制对轮廓处理的贡献。
