The new monodendritic neuronal type within the adult human cerebellar granule cell layer shows calretinin-immunoreactivity.

The distribution of calretinin immunoreactive structures within the granule cell layer of the adult human cerebellar cortex was studied using the avidin-biotin peroxidase method. Immunoreactivity is found in numerous fibers and glomerular formations, in Golgi- and Lugaro cells as well as in a recently described novel neuronal type, the monodendritic cell. The soma of the monodendritic neuron contains a faintly stained nucleus and issues a single short dendrite terminating in a tuft. Most probably, the tuft contributes to the formation of a glomerulum. Soma and tuft are of about the same size (diameter 10-18 microns). The number of monodendritic neurons is higher in the vermal than in the hemispheric part of the lobulus (lobulus VII) and is higher in lobulus X than in lobulus VII of the vermis.