The percentage of projection neurons and local circuit neurons in different nuclei of the human thalamus.

A characteristic lipofuscin pigmentation permits reliable distinction of the various neuronal types forming thalamic nuclei of the human adult. Type I projection cells with coarse and vacuolated lipofuscin granules are distinguished from type II local circuit neurons with fine and intensely stained pigment and type III neurons devoid of pigment. There is by no means a uniform ratio of projection neurons versus local circuit neurons. A high proportion of local circuit neurons is found in nuclei of the anterior complex, a medium proportion in the specific nuclei of the lateral complex, and a low proportion in the reticular nucleus. The technique and the data provided are being used as a basis for investigations of the diseased human brain.