Abstract
A number of recent studies have shown that extra-receptive-field (ERF) stimuli significantly can modulate V1 cells responses to intra-receptive-field (IRF) stimulus (e.g. iso-orientation inhibition, co-linear facilitation). It has been suggested that these effects are important for contour integration and texture segregation. We propose that the main function of the observed iso-orientation inhibition is to suppress the integration of low-level stimuli into contours when integration is undesirable (such as when co-linear stimuli is part of a surface texture rather than an occluding contour). A computational model is presented that integrates the output from model simple cells that are co-linear and similarly oriented. However, depending on the amount and the orientation of ERF stimuli, the integration mechanism can weight a model cells output differently. That is, the more similarly oriented ERF stimuli there is off the co-linear axis, the less will a model cells output be weighted by the integration mechanism. Computer simulations of the model produce results that in several aspects are consistent with human perception. For example, it accounts for phenomena such as illusory contours, contour masking and pop-out (due to orientation-contrast), and it relatively enhances image contours that human observers report as more salient.