The projection of the visual field to the lateral geniculate and medial interlaminar nuclei in the cat

Detailed and complete projection maps of the visual field to the whole of the dorsal lateral geniculate (LGNd) and medial interlaminar nucleus (MIN) of the cat have been prepared by plotting the receptive fields of single units in the two nuclei with tungsten‐in‐glass microelectrodes. The standard projection maps show the pattern of isoazimuths (“horizontals”) and isoelevations (“verticals”) in the two nuclei. Particular attention has been given to the projection of the upper visual field to the posterior part of the LGNd/MIN complex where the shape and relationship of the cellular laminae are changing rapidly. A separate projection of the visual field to the nucleus perigeniculatus (NPG) is also described, but the retinotopic organization of this projection is not as precise as for the LGNd and the MIN. Most of the cells in the NPG are binocularly‐activated and the receptive fields have ON/OFF centers. Further observations have been made concerning the distribution of the crossed and uncrossed fibers in the LGNd. In lamina B there is a thick dorsal zone of contralaterally‐activated cells and below this is a zone in which ipsilaterally‐activated cells are occasionally found. A few binocularly‐activated cells were found in the vicinity of the interlaminar regions.