The development of callosal projections in normal and one-eyed rats.

The course of callosal development in area 17 of rats suggests that, unlike immediately adjacent regions, axons of callosal origin do not normally gain access to upper cortical layers, and this results in the loss of an early exuberant callosal pathway. Removal of optic input, however, permits invasion of these layers of area 17 by callosal axons and results in survival of callosally projecting neurons in area 17.