Changes in the size of cells in the monocular segment of the primate lateral geniculate nucleus during normal development and following visual deprivation.

Cell areas have been measured in the monocular segment of the lateral geniculate nucleus in a series of 18 normal rhesus monkeys and in 27 following monocular or binocular lid closure or monocular enucleation. Cells in the parvocellular monocular segment shrank by 16% during the later period of normal development, between about 3 and 18 months of age, in contrasts to cells in the binocular segment which did not. Monocular closure at birth caused hypertrophy of cells in the undeprived monocular segment whereas long-term closure started later caused shrinkage of both deprived and undeprived parvocellular cells additional to that occurring during normal development. In both these instances cells in the monocular segment related to the undeprived eye are undergoing changes indicating some form of binocular interactions even in the monocular segment, but these interactions are considerably weaker than in the binocular part of the nucleus. Enucleation caused marked transneuronal degeneration of cells in the contralateral monocular segment of both infant and adult monkeys.