Lamination of the lateral geniculate nucleus in the squirrel monkey, Saimiri sciureus

The parvocellular portion of the lateral gesticulate nucleus (LGN) in the squirrel monkey ( Saimiri sciureus ) is a relatively unlaminated mass of cells. In order to determine whether a concealed laminar structure might exist, one eye was removed in each of three squirrel monkeys. Transneuronal degeneration did not appear prominent in the LGN of the animal which was allowed to survive for six months, but in the two animals which survived for one year six laminae were clearly present. There was transneuronal degeneration in layers 1, 4 and 6 contralateral to the enucleation, and 2, 3 and 5 ipsilaterally. Lack of interlaminar fiber masses probably accounts for the apparent absence of lamination in the normal parvocellular mass.