Retinotopic patterns of connections of area 17 with visual areas V‐II and MT in macaque monkeys

Abstract Patterns of connections of Area 17 with extrastriate visual areas V‐II and MT were studied in macaque monkeys by using 3 H‐proline and HRP as anatomical tracers. The results support previous conclusions that V‐II is a split representation of the visual hemifield with most of the outer border formed by the zero horizontal meridian, and that MT is a topological representation of the visual hemifield. V‐II was estimated to be about 10–12 mm wide, 110 mm long along its shared border with V‐I, and 920 mm 2 in surface area, thereby almost equaling Area 17 in size. MT was judged to be 7 mm wide and 12 mm long, with a surface area of 68 mm2, or roughly 7% of the area of Area 17. In some cases, there was evidence for projections from Area 17 to a third area (or areas) of cortex of about 2 mm wide and of uncertain length on the outer boundary of V‐II. Terminationsin V‐II and MT werecon‐centrated in layer IV and extended into inner layer III. Cells projecting back to Area 17 were largely in layers III and V in V‐II and in layers III and VI in MT.