Vision

Each visual cortex is about 2 in (5 cm) square and contains about 200 million nerve cells which respond to very elaborate stimuli. In primates, there are about 20 different visual areas in the visual cortex, the largest being the primary, or striate, cortex. The striate cortex sends information to an adjacent area which in turn transmits to at least three other areas about the size of postage stamps. Each of these areas then relays the information to several other remote areas called accessory optic nuclei. It is thought that the accessory optic nuclei plays a role in coordinating movement between the head and eyes so images remain focused on the retina when the head moves.

Figure 1. Illustration by Hans & Cassidy. Courtesy of Gale Group.