The unipolar brush cell (UBC) is a medium-sized neuron located in the granular 
layer of the cerebellar cortex and morphologically characterized by a single 
dendritic shaft terminated by a brush-like tuft [Mugnaini and Floris, J. Comp. 
Neurol., in press]. This neuronal class is mostly encountered in the vestibular 
part of the cerebellum, although also present in the rest of the vermal folia. 
The UBC axon, as seen in Golgi impregnated material, has a tortuous course 
throughout the granular layer and gives off number of collaterals of variable 
diameter. Some of the axon collaterals enter the white matter only for a short 
distance, after which they ascend into the granular layer. Astonishingly, some 
of the thick granular collaterals of these axons display characteristic 
expansions resembling the rosette excrescences seen on mossy fibers. In our 
series these rosettes are mostly of the simple type [Palay, S. and Chan-Palay, 
V., Cerebellar Cortex. Cytology and Organization, Springer, Berlin, 1974], i.e. 
short swellings with simple globular contours. The exact projection targets and 
functional effect of the UBC axon and granular rosettes have still to be 
demonstrated.