INTERACTIONS BETWEEN NASAL AND TEMPORAL HEMIRETINAL FIBERS IN ADULT GOLDFISH TECTUM

In adult goldfish the nasal half-retina from one eye and the temporal half-retina from the other eye were removed, followed by left tectal ablation. Visuotectal projections were later mapped electrophysiologically. The contralateral half-retina projected to the entire tectum and showed expansion of the visual field; the projection was orderly. Partially superimposed projections from the temporal half-retina of one eye and the nasal half-retina from the other eye were found in the middle of the tectum, whereas the rostral and caudal tectum were innervated exclusively by the appropriate half-retina. When temporal half-retinae from two eyes were ablated along with left tectal removal, some animals showed expansion of the contralateral half-retinal field onto the tectum; however, in other animals the ipsilateral projection innervated the tectum either partially or completely and the projections from two eyes were superimposed in mirror-image fashion. The results are discussed in relation to the mechanisms controlling selective fiber regeneration with underlying fiber-to-fiber interactions. © 1979.