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Yan Huang, Tiangang Zhou, Lin Chen; Double dissociations of Magnocellular and Parvocellular Pathways in Processing Global Topological and Local Properties. Journal of Vision 2013;13(9):353. doi: https://doi.org/10.1167/13.9.353.
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© ARVO (1962-2015); The Authors (2016-present)
The magnocellular (M) and parvocellular (P) pathways are segregated in anatomy as early as from the retina and lateral geniculate nucleus, as well as in function with M pathway conveying low-resolution information rapidly and P pathway conducting fine details slowly. Evidence shows that fast M projections facilitate object recognition via top-down modulations. Previous studies suggest global topological properties (TP), to which the visual system is highly sensitive, might serve as the starting point for the formation of object representations. Here we hypothesize that M pathway may contribute to fast object recognition by extracting TP in a visual scene and initiating a feedforward process, in addition to indirect feedbacks. We adopted unconscious response priming, a paradigm extensively used in studies on early vision, and used stimuli that were either of achromatic low-luminance contrast (M-biased), or chromatically defined and isoluminant (P-biased), to examine whether the processing of TP (e.g., number of holes) and other local properties (e.g., orientation) dissociate in the two pathways. To avoid potential confounding, we matched area and spatial frequency of stimuli. We found that priming effects of TP occurred with M-biased stimuli rather than P-biased ones, in both TP-relevant (i.e. discriminating no-hole from one-hole stimuli) and -irrelevant tasks (i.e. judging the orientation). Conversely, priming effects of orientation were observed only for P-biased stimuli, and only when orientation report was explicitly required. Moreover, the average response times (RTs) were shorter for TP judgment than those for orientation, and RTs were shorter for TP when stimuli were M-biased than when P-biased. Further measurement for prime identification showed neither of these properties in prime could be discriminated. Our findings suggest that M and P pathways are dissociated at the early stages of visual process, with M engaged in fast global TP extraction while P in slower local feature identification.
Meeting abstract presented at VSS 2013
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