Shape and contour detection

Detectability of contours may be affected by long-range interactions betwee n neurons in early stages of visual cortex. Specifically, neurons with rece ptive fields arrayed along the length of a contour may facilitate each othe r in a position- and orientation-dependent manner. Accordingly, the overall geometry of a contour should significantly influence both the strength of these long-range interactions and the contour's detectability. Psychophysic al experiments measuring the detectability of sampled, curvilinear contours hidden by randomly-oriented and -positioned noise elements revealed two ma in findings. First, changes in direction of curvature degraded contour dete ctability. Second, the effect of changes in magnitude of curvature were pre dicted by the average of local curvature along the length of the contour. W hile the first result emphasizes the importance of uniform direction of cur vature, the second result rules out penalties for deviation from circularit y. (C) 1998 Elsevier Science Ltd. All rights reserved.