A cytoarchitectonic study of zona incerta in the rat

The structural organization of zona incerta was studied in 11 brains of adult rats sectioned sagittally, transversally and horizontally and stained with cresylviolet. The following subregions could be differentiated on the basis of cytoarchitectural criteria: (1) pars rostro-polaris and (2) retro-polaris, (3) pars magnocellularis, (4) pars ventralis, (5) pars dorsalis and (6) pars caudalis. A sparcely populated zone, presumably a fiber layer, separates the ventral from the dorsal parts. The present findings are discussed in the light of a concomitant horseradish peroxidase study on efferent connections of zona incerta.