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Jordan Wagge, Lynn A Olzak; Visual integration in center/surround stimuli: Cortical mechanisms. Journal of Vision 2005;5(12):92. doi: https://doi.org/10.1167/5.12.92.
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Researchers have demonstrated a decrease in apparent contrast and in performance on spatial discrimination tasks when a center grating is surrounded by a high-contrast patterned annulus (Olzak & Laurinen, in press). Different effects are found when equal and low contrast surrounds are used. The purpose of this research was to determine whether combining mechanisms and/or lateral inhibitory interactions are involved when information is integrated over space under varying surround contrast conditions. An uncertainty paradigm (see Thomas & Olzak, 1996) was used to evaluate the relative contributions of these mechanisms. Performance was determined by taking the ratio of d' when observers did not know the location of the cue (center or surround) to when they knew the location in advance. All reported results are based on spatial frequency judgments. Two of three observers' preliminary data reject full summation, while preliminary data from the third observer did not.
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