Retinal Projections in the Tiger Salamander, Ambystoma tigrinum; pp. 401424

Degenerating retinofugal fibers and their terminal fields have been examined in the tiger salamander, Ambystoma tigrinum. The crossed pathway includes: (1) A large bundle which contains the poorly separated axial and marginal optic tracts. Fine particles presumed to be terminal or preterminal degeneration radiate from the tract toward the preoptic nucleus, form scanty diffuse fields in the ventral and dorsal thalamus, and form more compact fields in the neuropil of Bellonci, the pretectal neuropil and in the tectum. The tectal field is laminated. (2) A small bundle, the posterior accessory optic tract, which traverses the midbrain to terminate in a field just dorsal and rostral to the exiting oculomotor nerve. The uncrossed pathway passes through the ventral and dorsal thalamus as the most rostral fibers of the combined axial and marginal tracts and ends in the pretectal neuropil. Its terminal fields, except for the preoptic radiation, are the same as its more massive contralateral fellow. It does not enter the tectum. The relationship of the appearance of the stained particles to the postsurgical survival time is described.