On the nucleus endymalis of the human thalamus

In the present article the shape and extent of the nucleus endymalis in the human thalamus is described. By means of a newly developed method of selective staining of intracellular lipofuscin granules with aldehydefuchsin it is possible to examine the three-dimensional shape of the griseum in complete series of 800 micrometer thick slices. The nucleus endymalis can be divided into an invariably occurring strongly pigmented caudal pars pigmentosa with clear-cut boundaries and an oral pars commissuralis. The weakly pigmented oral part is only found in brains with developed massa intermedia and varies considerably from individual to individual. The pars pigmentosa is characterized by its periventricular position medial to the nucleus parafascicularis. Differences in nomenclature and outlines of topographically corresponding thalamic nuclei of other authors are discussed. It is assumed that the pars pigmentosa a least partly corresponds to the catecholaminergic cell group A11 in the rat brain (Dahlström and Fuxe 1964). Finally, its possible functional connections to the dorsal periventricular bundle and its significance for stimulation-produced analgesia (SPA) in man are discussed.