- The main role of oligodendrocytes in the central nervous system (CNS) is the formation of the myelin sheath around axons.
- This myelin sheath is essential for the rapid conduction of electrical impulses along the neuron, allowing for efficient communication between nerve cells.
- Unlike Schwann cells in the peripheral nervous system, a single oligodendrocyte can extend its processes to multiple axons, myelinating several segments simultaneously.

- While other cells in the CNS have different functions—such as microglia performing phagocytosis of neuronal debris (Option 2) and astrocytes providing metabolic support to neurons (Option 4)—the primary responsibility of oligodendrocytes remains myelination.
- This specialized role supports neural signal transmission and contributes to the overall functionality of the nervous system.

In summary, the correct answer is Formation of myelin sheath around axons because oligodendrocytes are the principal myelinating cells in the CNS.

Reference: Neuroscience, 6th Edition, Volume 1, Chapter 4, Page 120