Pontocerebellar system linking the two hemispheres by intracerebellar branching.

Origin and percentage of bilaterally projecting pontocerebellar neurons whose axons branch within the cerebellum and link the two cerebellar hemispheres were studied in cats using double retrograde fluorescent tracing and lesion techniques. These pontocerebellar neurons, which can be viewed as a separate component of the pontocerebellar system, account for 5-10% of the pontine neurons projecting to the lateral hemisphere. The system is mainly composed of neurons the axons of which recross within the cerebellum. The pontocerebellar interhemispheric system described here is likely to be the basis for the previously described intracerebellar commissural system. The bilateral distribution of these fibers may provide an important substrate for the coordination of bilaterally performed movements.