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Neural mechanisms of perceptual grouping in human visual cortex

Chinese Science Bulletin 2004年第8期49卷 819-823页

作者： MAOLihua hanshihui GUOChunyan JIANGYi DepartmentofPsychology CenterforBrainandCognitiveSciencesPekingUniversityBeijing100871China Learning&CognitionLab CapitalNormalUniversityBeijing100037China

The current work examined neural substrates of perceptual grouping in human visual cortex using event-related potential (ERP) recording. Stimulus arrays consisted of local elements that were either evenly spaced (uniform stimuli) or grouped into columns or rows by prox-imity or color similarity (grouping stimuli). High-density ERPs were recorded while subjects identified orientations of perceptual groups in stimulus arrays that were presented randomly in one of the four quadrants of the visual field. Both uniform and grouping stimulus arrays elicited an early ERP component (C1), which peaked at about 70 ms after stimulus onset and changed its polarity as a function of stimulated elevations. Dipole modeling based on realistic- head boundary-element models revealed generators of the C1 component in the calcarine cortex. The C1 was modu-lated by perceptual grouping of local elements based on proximity, and this grouping effect was stronger in the upper than in the lower visual field. The findings provide ERP evi-dence for the engagement of human primary visual cortex in the early stage of perceptual grouping.

关键词：钙质皮层事件相关潜力知觉分组接近性神经系统视觉皮层

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Modulation of human global/local perception by low spatial frequency filtering

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Chinese Science Bulletin 2003年第21期48卷 2336-2339页

作者： hanshihui J.A.Weaver S.O.Murray KANGXiaojian E.W.Yund D.L.Woods DepartmentofPsychology CenterforBrainandCognitiveSciencesPekingUniversityBeijing100871China DepartmentofNeurology UniversityofCaliforniaatDavisVANorthernCaliforniaSystemofClinicsDavisCA95616USA

We investigated the effect of low spatial fre-quency (SF) filtering on neural substrates underlying global and local processing in the peripheral vision by measuring hemodynamic responses with functional magnetic resonance imaging (fMRI). Subjects identified global or local shapes of compound letters that were either broadband in spatial- frequency spectrum or contrast balanced (CB) to removed low SFs and displayed randomly in the left or right visual fields. Attention to both broadband and CB global shapes generated stronger activation over the medial occipital cor-tex relative to local attention. Lateralized activations in association with global processing were observed over the right temporal-parietal junction for broadband stimuli whereas over the right fusiform gyrus for CB stimuli. Atten-tion to CB local shapes resulted in activations in the medial frontal cortex, bilateral inferior frontal and superior tempo-ral cortices. The results were discussed in terms of the competition between global and local information in determining brain activations in association with global/local processing of compound stimuli.

关键词：神经系统血液动力学功能磁性共振图空间频率光谱

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