Architectonic differentiation of the lateral geniculate body of the cat.

The cell layers of the lateral geniculate nucleus (LGN) of the cat have been reinvestigated in relation to the localization of the degeneration of optic terminals. After unilateral enucleation the degenerated crossed and uncrossed optic terminals form five continuous alternate strips in all the five layers of the LGN with the Fink-Heimer method. The crossed terminals end in the layers A, B0, and B2, and the uncrossed terminals in the layers A1, and B1 without overlapping. The cyto- and myeloarchitectonic study of complete frontal, sagittal, and horizontal serial sections has shown that the former B layer and the nuclei interlaminares centralis pars ventralis and medialis of Thuma built up three continuous parallel layers, which we propose to call B0, B1, and B2. The layer B0 containing large cells and more single fibers than the layers A and A1, extends on the medial, ventral and caudal side of layer A1. The layer B1 containing smaller cells and less single fibers than the layer B0, surrounds the layer B0 from medial, ventral and caudal. It comprises in the medial part of the ventral extent a pale spot with especially small nerve cells. The layer B2 containing medium-sized cells in less dense arrangement and many small dark fiber bundles split up from optic tract extends medially and ventrally of layer B1. The caudal pole of the LGN is covered cap-like by the layers B0, and B1 and incompletely by B2. This new interpretation of the LGN's layers in the cat is more regular and easier to compare with the stratification of the LGN of other species including primates.