Fig. 1

a The calcarine sulcus (CS) begins near the occipital pole on the medial surface of a cortical hemisphere and continues toward the posterior end of the corpus callosum (thick black line). This is the site of V1. Its border is marked with a dashed line. b Medial side of the occipital pole, as in a but with straight course of CS. c The approximate 3D form of V1 in the $(u,v,l)$ coordinates (see text). The representations of the two vertical meridians are dashed and the fundus of CS is marked with a thick black line. d The retinal surface is approximated by a quarter of a sphere, or e by a flat disc, as assumed in many experimental data. f A Cartesian reference coordinate system of the visual field (${\xi }_1,{\xi }_2$). g and h Coronal section through V1. The red line traces the stria of Gennari. The M–L axis indicates the medial to lateral axis