Morphological studies of local circuit neurons in the cerebellar dentate nucleus of man.

Golgi preparations reveal the existence of two classes of nerve cells in the human dentate nucleus. Relatively large principal cells predominate. Small local circuit neurons are scattered throughout the nuclear gray. By means of a newly developed de-impregnation technique the pattern of pigmentation of both cell types can be studied. The principal cells show a considerable amount of finely granulated and faintly tinged pigment, whereas the local circuit neurons contain only a few large and intensely stained lipofuscin granules. The local circuit neurons give off a few smoothly contoured and rather extended dendrites. The axon is generated from either the cell body or a dendrite by way of a cone-shaped initial portion. A thin thread-like segment follows. Further distally, the caliber of the axon increases abruptly. This thick portion branches off several times at short intervals giving off fine processes with bead-like enlargements. Occasionally, a second axon is generated from these cells.