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 (unif...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.展开更多
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 reso...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.展开更多
文摘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.
基金supported by the National Natural Science Foundation of China(Grant No.30225026)the Ministry of Science and Technology of China(Grant No.2002CCA01000)+1 种基金the National Institutes of Mental Health(Grant No.N1MH-41544)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,the Ministry of Education of China,and Peking University.
文摘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.
