Cell size changes in undeprived laminae of monkey lateral geniculate nucleus after monocular closure

Abstract

Transneuronal degeneration in the lateral geniculate nucleus (LGN) due to removal of an eye or closure of the eyelids has traditionally been measured by comparing the sizes of cells in the deprived laminae with those of the corresponding undeprived laminae in the nucleus of the opposite side of the same brain. However, the undeprived laminae may themselves change; some hypertrophy of their cells has been found in kittens following early monocular closure¹ but such comparisons are difficult in the cat because of the variation between animals². In a recent study of the effect of binocular closure in the monkey³ it was necessary to measure cell sizes in the LGNs of a series of normal monkeys as controls, because there are no undeprived laminae after binocular closure. From this series of normal animals it was apparent that there is much less variation between individual monkeys than has been found with cats and it was thus possible to make reliable comparison of cell sizes between different animals. In the present study the series of normal monkeys has been extended and the mean cell size and its variability between animals have been established for each geniculate lamina in the normal rhesus monkey. We give here a comparison of the cell sizes of both deprived and undeprived laminae following monocular eyelid closure with normal measurements and report some unexpected findings, particularly in animals where monocular closure has been carried out relatively late.