The distribution of crossed and uncrossed optic fibers in the different layers of the lateral geniculate nucleus in the tree shrew (Tupaia glis).

Abstract

The laminar distribution of crossed and uncrossed optic fibers was studied in the lateral geniculate nucleus (LGN) in the tree shrew (Tupaia glis) following unilateral enucleation. For the investigation of the termination of optic fibers the transneuronal degeneration method and experimental EM were employed. By using formvar film-coated slot grids, all six layers of the LGN could be studied in a single ultrathin section. Degeneration of crossed optic fibers was observed in layers 1, 3, 4 and 5 of the contralateral LGN. The uncrossed retinofugal fibers supply layers 2 and 6 of the LGN. The degeneration in layer 4 was less pronounced than that in the other layers. Ipsilateral and contralateral optic fibers were well separated. Filamentous as well as dark types of degeneration were found in the LGN after enucleation. The optic terminals (RL boutons) were seen only in the synaptic glomeruli.