Xiang Wu

Publications (3)13.88 Total impact

• Article: Dissociable neural correlates of contour completion and contour representation in illusory contour perception.

  Xiang Wu, Sheng He, Khalaf Bushara, Feiyan Zeng, Ying Liu, Daren Zhang
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  ABSTRACT: Object recognition occurs even when environmental information is incomplete. Illusory contours (ICs), in which a contour is perceived though the contour edges are incomplete, have been extensively studied as an example of such a visual completion phenomenon. Despite the neural activity in response to ICs in visual cortical areas from low (V1 and V2) to high (LOC: the lateral occipital cortex) levels, the details of the neural processing underlying IC perception are largely not clarified. For example, how do the visual areas function in IC perception and how do they interact to archive the coherent contour perception? IC perception involves the process of completing the local discrete contour edges (contour completion) and the process of representing the global completed contour information (contour representation). Here, functional magnetic resonance imaging was used to dissociate contour completion and contour representation by varying each in opposite directions. The results show that the neural activity was stronger to stimuli with more contour completion than to stimuli with more contour representation in V1 and V2, which was the reverse of that in the LOC. When inspecting the neural activity change across the visual pathway, the activation remained high for the stimuli with more contour completion and increased for the stimuli with more contour representation. These results suggest distinct neural correlates of contour completion and contour representation, and the possible collaboration between the two processes during IC perception, indicating a neural connection between the discrete retinal input and the coherent visual percept. Hum Brain Mapp 33:2407-2414, 2012. © 2011 Wiley Periodicals, Inc.
  Human Brain Mapping 08/2011; 33(10):2407-14. · 5.88 Impact Factor
• Article: Early induced beta/gamma activity during illusory contour perception.

  Xiang Wu, Daren Zhang
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  ABSTRACT: The temporal binding hypothesis proposes that visual feature binding is achieved by neuronal synchronization. Nevertheless, the existing human neurophysiological evidence for the neuronal synchronization in visual feature binding-the oscillatory induced beta/gamma activity (IB/GA) is under suspicion. The previously observed IB/GA occurs at a later stage (after 200 ms), thus leading to the objection that IB/GA may be related to some later top-down processes rather than the early perceptual processing. However, the present EEG study identified an IB/GA as early as 90 ms after stimulus onset, which was stronger for a Kanizsa-type illusory contour (IC, a classic example of visual feature binding) than for a control stimulus. This finding provides new human evidence for the temporal binding hypothesis that neuronal synchronization occurs at the early stage of visual feature binding.
  Neuroscience Letters 11/2009; 462(3):244-7. · 2.11 Impact Factor
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  Available from: ccmu.edu.cn

  Article: Binding of verbal and spatial information in human working memory involves large-scale neural synchronization at theta frequency.

  Xiang Wu, Xiangchuan Chen, Zhihao Li, Shihui Han, Daren Zhang
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  ABSTRACT: Whether neural synchronization is engaged in binding of verbal and spatial information in working memory remains unclear. The present study analyzed oscillatory power and phase synchronization of electroencephalography (EEG) recorded from subjects performing a working memory task. Subjects were required to maintain both verbal (letters) and spatial (locations) information of visual stimuli while the verbal and spatial information were either bound or separate. We found that frontal theta power, and large-scale theta phase synchronization between bilateral frontal regions and between the left frontal and right temporal-parietal regions were greater for maintaining bound relative to separate information. However, the same effects were not observed in the gamma band. These results suggest that working memory binding involves large-scale neural synchronization at the theta band.
  NeuroImage 06/2007; 35(4):1654-62. · 5.89 Impact Factor