The Neural Control of Vision
M. The Processing of Shape

Yet another theory of how we are capable of processing shape information derives from the fact that the visual field is laid out in an orderly fashion in numerous brain structures. One of the first individuals to deal with this question was Cajal who asked why the optic nerve crosses over at the optic chiasm, completely in some species with laterally placed eyes, and partially in mammals with forward looking eyes as noted in Figure 1. Cajal argued that the reason is that as a result of such crossing the integrity of the visual scene is maintained in the brain. This is demonstrated in Figure 68 showing that an arrow is represented in an orderly fashion only when the optic nerves cross (B).