Perception of contours and shapes: low and intermediate stage mechanisms

This review focuses on low and intermediate stages of contour shape processing. It is split into two main sections, ‘Contour Detection’ and ‘Shape Discrimination and Representation’. The first section examines contrast detection of elements within a contour (“collinear facilitation”) and the detection of contours in noise (“contour integration”). The second section deals with the discrimination and representation of simple and complex shapes. Perceptual effects on contour detection have been linked to low-level, long-range lateral interactions between neighbouring neurons in V1. Experimental results suggest a complex network of interactions that are context dependent, with collinearity being the dominant factor.