We performed psychophysical experiments using path-paradigm addressing whether 3D convex/concave contour was encoded in separate neurons or not. The stimulus element composed of two equilateral triangles that share one of their edges, and each triangle has dots in its inner region. The stimulus elements have 3D convex/concave structure with a bend. In experiment 1, we used three types of paths: homogeneous concave elements, homogeneous convex, elements, and alternation of convex I concave elements. The rest stimulus elements are arranged randomly. We obtained the result that subjects could not detect alternating path well. In experiment 2, we used only two types of paths: homogeneous concave elements, homogeneous convex, elements. Subject can detect well them equally. These results suggest that the visual system has separate neurons processing 3D convex/concave edges.
