The ponto-cerebellar filaments start from the pons nuclei, cross the mean line and enter the opposite side of the cerebellar half via the middle cerebellar arm.
Once the ponto-cerebellar filaments enter the cerebellum, they divide Y-shaped. One group of Y-branches enters the cerebellar nuclei, especially into the dentatus nucleus, and the other group continues out into the cerebellar cortex, especially out into the cerebrocerebellum, in the form of moss filaments.