Primary Cortical Dynamics for Visual Grouping

The classical receptive elds of V1 neurons contain only local visual input features. The visual system must group separate local elements into meaningful global features to infer the visual objects in the scene. Local features can group into regions, as in texture segmen-tation; or into contours which may represent boundaries of underlying objects. I propose that the primary visual cortex (V1) contributes to both kinds of groupings with a single mechanism of cortical interac-tions/dynamics mediated by the horizontal connections, and that the dynamics enhance the saliencies of those features in the contours (compared with those in a noisy background) or near the region boundaries (compared with those away from the boundaries). Visual inputs specify the initial neural activity levels, and cortical dynamics modify the neural activities to achieve desired computations. Contours are thereby enhanced through dynamically integrating the mutual facilitation between contour segments, while region boundaries are manifested (and enhanced) in the dynamics because of the breakdown of translation in-variance in image characteristics at the region boundaries. I will show analytically and empirically how global phenomena emerge from local features and nite range interactions, how saliency enhancement relates to the contour length and curvature, and how the neural interaction can be computationally designed for region segmentation and gure-ground segregation. The structure and behavior of the model are consistent with experimental observations.