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Nonlinear interactions between contour elements in the classical and extraclassical receptive field

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The responses of complex cells in V1 to oriented bars can be nonlinearly boosted by "contextual" inputs consisting of co-linear flankers in the extraclassical receptive field. However, it is not known whether (i) each distinct simple-cell-like subunit within a complex cell's receptive field is subject to a separate subunit-specific contextual influence, (ii) whether the long-range contextual input modulates only a single classical RF subunit, or (iii) whether the contextual input acts uniformly and globally on all subunits of the cell. Three different lines of evidence bearing on this question will be discussed, including (1) contour-detection performance in natural images using a computer model of V1; (2) preliminary data relating to classical-extraclassical contour alignment in monkey V1 (in collaboration with Wyeth Bair); and (3) results of compartmental modeling studies relating on the "contextual" processing capabilities of individual pyramidal neurons.