Binocular Segregation in the Dorsal Lateral Geniculate Nucleus

Abstract

In most mammals the optic nerve fibres from the two eyes terminate in separate layers in the dorsal lateral geniculate nucleus (LGNd). The layers of retinal input in the LGNd can be revealed by transneuronal degeneration of cells in the LGNd or anterograde optic fibre degeneration following removal of one eye, by transport of radioactive amino acids to the optic terminals in the LGNd or by electrophysiological recording of single neurons in the LGNd. The laminar organisation of the LGNd is described in man, rhesus monkey, cat and some Australian marsupials. In Australian possums and kangaroos the optic fibres from the two eyes terminate in separate layers in the LGNd whereas in the Australian carnivorous marsupials there is significant overlap of optic fibres from the two eyes in the LGNd. The development of the normal laminar organisation of the LGNd is described for a number of species. Early in development there is little evidence of lamination in the LGNd and optic fibres from both eyes spread over the whole LGNd. The adult pattern of lamination generally appears at birth or shortly afterwards. Binocular interaction in the LGNd is described in the cat, where it arises both from intrageniculate circuits and via binocular cortico-geniculate fibres. It is suggested that the function of lamination in the LGNd is to provide separate channels for some of the different types of information brought in from the retina.