Anatomy of the cerebellum and the role played in normal cerebellar function). From the phylogenetically oldest to the newest, the three parts are: Much of what is understood about the functions of the cerebellum stems from careful documentation of the effects of focal lesions in human patients who have suffered from injury or disease or through animal lesion research. As explained in more detail in the Function section, the cerebellum differs from most other brain areas in that the flow of neural signals through it is almost entirely unidirectional: there are virtually no backward connections between its neuronal elements. Thus the most logical way
Anatomy of the cerebellum the numerous and tiny granule cells, the slightly larger unipolar brush cells and the much larger Golgi cells. Mossy fibers enter the granular layer from their main point of origin, the pontine nuclei. These fibers form excitatory synapses with the granule cells and the cells of the deep cerebellar nuclei. The granule cells send their T-shaped axons—known as parallel fibers—up into the superficial molecular layer, where they form hundreds of thousands of synapses with Purkinje cell dendrites. The human cerebellum contains on the order of 60 to 80 billion granule cells, making this single cell type by far the most