The plan of the proposed research is an anatomical study of the laminar development of the dorsal lateral geniculate nucleus (LGN) in tree shrew. This will involve study of the factors involved in the laminar or functional organization of the LGN. In addition, it will involve study of developmental mechanisms which not only play a role in laminar formation but could also contribute to cytoarchitectural development throughout the developing nervous system. The approach will include light and electron microscopy and utilize experimental techniques of horseradish peroxidase and autoradiography to study normal development as well as the effect of deafferentation on the LGN. Work in normal animals will include studies of synaptogenesis, cellular morphology, dendritic growth cones, and naturally occurring cell death or neurothanasia. Work in animals with enucleations, partial retinal lesions, or collicular lesions will include studies of specificity of LGN connections, lamination of LGN afferents, and LGN interlaminar space formation. Understanding normal developmental mechanisms involved in formation of visual system organization as well as the effect of complete or partial absence of retinal afferents will be useful in appreciating the full impact and consequences of numerous clinical conditions. Environmentally induced anomalies, genetic anomalies, and intrauterine anomalies due to maternal disease include anophthalmia, microphthalmia, chorioretinal lesions, and optic atrophy. The tree shrew has been chosen as the experimental animal since it is a prototypical primate, has a highly organized visual system, is born more immature than any higher primate, breeds readily, and has multiple young and a short gestation.
