White matter

Arbor vitae

Also called Cerebellar white matter, Tree of life

The "tree of life": branching white wiring hidden inside the cerebellum.

Open in 3D

Cut the cerebellum down the middle and you see a beautiful pattern: pale branches spreading out like a tree. That tree is the arbor vitae, the cerebellum's white matter. It is made of bundles of nerve fibers carrying signals into and out of the cerebellum's wrinkled surface. The fibers look white because they are wrapped in myelin, a fatty coating that speeds up signals.

Where it is

Inside the cerebellum, under its thin gray surface layer. You can only see it when the cerebellum is cut open.

What it does

Think of it as the trunk and branches of a real tree, carrying sap out to every leaf and back again.

Works with

• Deep cerebellar nucleiThe deep nuclei are buried among its branches, like fruit hidden inside a tree.
• Purkinje cellThe long output fibers of Purkinje cells run through it to reach the deep nuclei.
• Mossy fibersThese incoming fibers travel through its branches to reach the cerebellum's surface.
• Climbing fibersThese fibers from the lower brainstem pass through it to wrap around Purkinje cells.
• PonsThe biggest of its three stalks brings in a flood of signals from the pons.
• Myelin sheathMyelin wrapping around its fibers is what gives this tree its white color.

When it goes wrong

For learning only, not medical advice. If you have a health concern, talk to a doctor.

Surprising facts

• The thin folds of the cerebellum are called folia, Latin for "leaves". So this tree even comes with its own leaves.
• A popular garden evergreen, the thuja, is also called arborvitae. It shares the very same "tree of life" name.

Where the name comes from

Latin for "tree of life", after its branching, tree-like pattern.

Learn it in a lesson

• The cerebellumSmooth, balanced, well-timed movement. A short guided lesson in 3D.

Sources

1. Neuroanatomy, Cerebellum, StatPearls, NCBI Bookshelf
2. Histology, Myelin, StatPearls, NCBI Bookshelf
3. Organization of the Cerebellum, Neuroscience, 2nd edition (Purves et al.), NCBI Bookshelf

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