inferior olivary nucleus

The inferior olivary nuclei (or ION) are two C-shaped nuclei located within the medulla oblongata, implicated in motor co-ordination.

Gross anatomy

The inferior olivary nuclei are located in the superior medulla, just below the pons. They are an irregular mass of crenated C-shaped grey matter, with a medially-directed hilum. A large amount of fibers travel to and from the nucleus via the hilum. The open side of the C-shape faces the opposite inferior cerebellar peduncle.

The inferior olivary nucleus has prominent connections to the cerebellum. These small neurons form the olivocerebellar tract. Fibers decussate across the midline to enter the inferior cerebellar peduncle.

The superior olivary nuclei are smaller and are located in the pons.


The inferior olivary nuclei are implicated in motor co-ordination. They may have oscillatory-pacemaking functions, and play a role in the pathogenesis of essential tremor.

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