Contour-Induced Multiple Modulatory Effects in V1 and V2 Previous V1 studies have shown that global visual contours within a cluttered background induce two complementary modulatory effects (Chen et al., 2014; Gilad et al., 2013; Yan et al., 2014): enhancing responses of neurons with RFs lying on the contour (referred to as the contour facilitation) and suppressing neurons with RFs in the background (referred to as the background inhibition).