For reasons that are not understood, only the larger diameter (>∼1 μm) axons of peripheral nerves are myelinated — smaller axons lie in troughs in the surface of non-myelinating Schwann cells.

For example, fibers or thick nerve bundles are visible in a section but it’s hard to know which cell body the fibers came from. Researchers can still learn a lot from the fibers at the RNA level ...

White matter allows the brain to function as a connected whole. These myelinated nerve fiber tracts transmit information between regions quickly and efficiently. Unlike gray matter, which is tied to ...