An experimental anatomical study on the topographic termination of the optic nerve fibers in the rat.

The topographic termination of the optic nerve fibers was studied in the rat by using a silver impregnation method for degenerating nerve fibers. Male and female albino rats of Gifu and Wistar strains weighing 170 to 360 gm were used, and each quadrant of the right retina was injured by trans-scleral coagulation. The degenerating nerve fibres were examined in the ventral and dorsal halves of the optic tract, ventral and dorsal nuclei of the lateral geniculate body, and the superior colliculus on the left side, as well as in the right optic nerve. The retinal fibers seem not to change their relative positions much in the optic nerve, but they rotate counterclockwise 45 to 90 degrees in the dorsal half of the optic tract when they are observed from the retinal direction. The fibers project to both nuclei of the lateral geniculate body with a reversal in their dorsoventral relationship but no change in their relative nasotemporal positions. In the superior colliculus, most of these fibers project to the superficial gray stratum. At the site of projection in the superior colliculus these fibers, when observed from the retinal direction, are rotated counterclockwise about 180 degrees from their position in the retina.