White matter of the cerebellum
The central core of each cerebellar hemisphere is formed by white matter. The peduncles are continued into this white matter. The white matter of the two sides is connected by a thin lamina of fibres that are closely related to the fourth ventricle. The upper part of this lamina forms the superior medullary velum , and its inferior part forms the inferior medullary velum. Both these take part in forming the roof of the fourth ventricle.
The white matter consists of:
a. Afferent fibres entering the cerebellum from outside.
b. Projection fibres from the cerebellar cortex to the cerebellar nuclei.
c. Association fibres interconnecting different parts of the cerebellar cortex.
d. Commissural fibres connecting the two cerebellar hemispheres.
e. Fibres from the cerebellar nuclei (and some from the cerebellar cortex) to centres outside the cerebellum.