SPATIAL-FREQUENCY TUNING OF VISUAL CONTOUR INTEGRATION

We examine the mechanism that subserves visual contour detection and p articularly its tuning for the spatial frequency of contour components . The measured the detection of contours composed of Gabor micropatter ns within a held of randomly oriented distracter elements. Distracters were randomly assigned one of two spatial frequencies, and elements l ying along the contour alternated between these values. We report that the degree of tolerable spatial-frequency difference between successi ve contour elements is inversely proportional to the orientation diffe rence between them. Spatial-frequency tuning (half-width at half-heigh t) for straight contours is similar to 1.3 octaves but, for contours w ith a 30 degrees difference between successive elements, drops to simi lar to 0.7 octaves. Integration of curved contours operates at a narro wer bandwidth. Much orientation information in natural images arises f rom edges, and we propose that this narrowing of tuning is related to the reduction in interscale support that accompanies increasing edge c urvature. (C) 1998 Optical Society of America.