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Robert Fendrich, Paul Corballis, Bjoern Schott; Mechanisms of visual grouping investigated with fMRI. Journal of Vision 2001;1(3):387. doi: https://doi.org/10.1167/1.3.387.
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We used functional magnetic resonance imaging to investigate the neural substrate of the processes that group visual elements into figures. In different blocks, subjects viewed a sequence of pentagons that were either drawn from lines or made up of five dots which marked their apexes. In both cases, the figures switched randomly between 4 possible orientations (apex up, down, left, right), at a rate of 2 presentations per second. After each block, subjects were asked which pentagon orientation had been presented most frequently. The sole purpose of this task was to motivate the subjects to attend continuously to the figures. Each of 10 subjects viewed 16 dot and 16 line presentation blocks in a counterbalanced order. Each block lasted 20 seconds and was followed by a 20 second fixation period. Figures were presented on a rear projection screen and cerebral BOLD-EPI responses were measured with a 1.5T GE Signa MRI scanner. We observed greater bilateral activity in the fusiform gyrus of prestriate cortex in the dot presentation blocks than in the line presentation blocks. This is a region which previous fMRI investigations have implicated in the processing of figures. Our result suggests that the binding of discrete non-contour visual elements into figural gestalts may begin quite early in the visual processing hierarchy.
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