Showing papers by "Paul Sajda published in 1993"

Cortical Mechanisms for Surface Segmentation

Abstract: Physiology has shown that the neural machinery of “early vision” is well suited for extracting edges and determining orientation of contours in the visual field. However, when looking at objects in a scene our perception is not dominated by edges and contours but rather by surfaces. Previous models have attributed surface segmentation to filling-in processes, typically based on diffusion. Though diffusion related mechanisms may be important for perceptual filling-in [4], it is unclear how such mechanisms would discriminate multiple, overlapping surfaces, as might result from occlusion or transparency. For the case of occlusion, surfaces exist on either side of a boundary and the problem is not to fill-in the surfaces but to determine which surface “owns” the boundary [1][3]. This problem of boundary “ownership” can also be considered a special case of the binding problem, with a surface being “bound” to a contour.

Dual Mechanisms for Neural Binding and Segmentation

Abstract: We propose that the binding and segmentation of visual features is mediated by two complementary mechanisms; a low resolution, spatial-based, resource-free process and a high resolution, temporal-based, resource-limited process. In the visual cortex, the former depends upon the orderly topographic organization in striate and extrastriate areas while the latter may be related to observed temporal relationships between neuronal activities. Computer simulations illustrate the role the two mechanisms play in figure/ground discrimination, depth-from-occlusion, and the vividness of perceptual completion.