Topography of the cortico-cortical connections from the striate cortex in the cat

Injections of radioactive amino acids were placed in regions of the striate cortex of cat representing central, intermediate and peripheral parts of the horizontal meridian and also in regions of lower and upper visual field representations near the vertical meridian. The study of cortico-cortical connections arising from these points revealed several retinotopic arrangements in the distribution of these connections and, it is argued, of the extrastriate cortical recipient areas themselves. On retinotopic distribution exists along the banks of the middle suprasylvian sulcus, in which lower and upper visual fields are rostral and caudal, respectively, and central and peripheral visual fields are ventral (or lateral) and dorsal (or medial), respectively, in the banks. This arrangement is called the lateral suprasylvian area (LS). Another retinotopic distribution exists along the caudal bank of the posterior suprasylvian sulcus. In this region, called the posteroior suprasylvania area(PS), points at, or near, the horizontal meridian are mainly represented, central and peripheral parts of which are located dorsaly and ventrally in the sulcus, respectively. Two other retinotopic distributions of connected exist in visual areas 2(V2) and 3 (V3) of Hubel and Wiesel, in which lower and upper visual fields are situated rostrally and caudally in these areas, respectively. Along the horizontal meridian, central is lateral in V3 and medial in V2, while more peripheral points, (15 degrees, 45 degrees) of V3 and V2 approach each other, in a mirror image fashion, along the coronal plane. However, representations of these peripheral parts of the horizontal meridian are repeated twice again: extensively, caudally along the lateral border of area 18, and more restrictively rostrally, along the lateral border of area 18.