Mossy fiber (cerebellum)

They ascend into the white matter of the cerebellum, where each axon branches to innervate granule cells in several cerebellar folia.

In this case, the pathway is so named for a unique synapse formed by its projections, the mossy fiber rosette.

Fine branches of the mossy fiber axons twist through the granule cell layer, and slight enlargements giving a knotted appearance indicate synaptic contacts.

These contacts have the appearance of a classic Gray's type 1 synapse, indicating they are glutamatergic and excitatory.

Extensive branching in white matter and synapses to granular cells ensures that input from a single mossy fiber axon will influence processing in a very large number of Purkinje cells.

Microcircuitry of the cerebellum. Excitatory synapses are denoted by (+) and inhibitory synapses by (-). MF: Mossy fiber. DCN: Deep cerebellar nuclei. IO: Inferior olive . CF: Climbing fiber . GC: Granule cell. PF: Parallel fiber . PC: Purkinje cell . GgC: Golgi cell. SC: Stellate cell. BC: Basket cell.