Ontogenetic development and maintenance of compensatory eye movements in complete absence of the optic nerve.

Abstract

At an early age, the right eyes of donor tadpoles (@@Rana clamitans@) were transplanted to the left orbit of new hosts. In one group, the contralateral eye of the host was excised at a time when rods and cones are just beginning to differentiate; in another group this was done 2 mos. later. Seven animals in the 1st group and 9 in the 2d never acquired any vision in the transplanted eye, nor did the optic nerve reach the brain in these animals. Eye movements compensating for movement of the support in 2 vertical planes were observed in all but 1 of these animals in tests 40 days post-operatively. Some animals evincing abnormal response in the test situation were found to have structural abnormalities of muscular development or orientation of the eyeball. It is concluded that the reflex associations of the vestibulo-ocular system in these animals are not patterned by training but are laid down directly in growth in a predetermined manner.