Development of the nervous system in humans optical vesicle (which will eventually become the optic nerve, retina and iris) forms at the basal plate of the prosencephalon. In the fifth week, the alar plate of the prosencephalon expands to form the cerebral hemispheres (the telencephalon). The basal plate becomes the diencephalon. The diencephalon, mesencephalon and rhombencephalon constitute the brain stem of the embryo. It continues to flex at the mesencephalon. The rhombencephalon folds posteriorly, which causes its alar plate to flare and form the fourth ventricle of the brain. The pons and the cerebellum form in the upper part of the rhombencephalon, whilst the medulla oblongata forms
Anatomy of the cerebellum would go to mossy fibers that synapse with granule and Golgi neurons with the granule cells then targeting Purkinje neurons via their excitatory parallel fibers. If the inferior olive it would go via excitatory climbing fiber inputs to Purkinje neurons. These return this output back to the cerebral cortex through the ventrolateral thalamus completing the loop. The corticopontocerebellar pathway is the largest pathway associated with the cerebellum. Arising in the cerebral cortex these fibers first terminate ipsilaterally in the pontine nuclei. Then the fibers decussate and form the middle cerebellar peduncle, terminating in the cerebellar cortex as mossy fibers. This