Inferior olivary nucleus

The inferior olivary nucleus is the largest nucleus situated in the olivary body, part of the medulla oblongata.

It consists of a gray folded lamina arranged in the form of an incomplete capsule, opening medially by an aperture called the hilum.

Emerging from the hilum are numerous fibers that collectively constitute the peduncle of the olive. The axons, also known as olivocerebellar fibers, leave the olivary nucleus, exit through the hilum, and decussate with those from the opposite olive in the raphé.

Then, as internal arcuate fibers, they pass partly through and partly around the opposite olive and enter the inferior peduncle to be distributed to the cerebellar hemisphere of the opposite side from which they arise.

The fibers are smaller than the internal arcuate fibers connected with the medial lemniscus.

Fibers passing in the opposite direction from the cerebellum to the olivary nucleus are often described, but their existence is doubtful.

Much uncertainty exists also with regard to the connections of the olive and the spinal cord.

Important connections between the cerebrum and the olive of the same side exist, but the exact pathway is unknown.

Many collaterals from the reticular formation and from the pyramids enter the inferior olivary nucleus.

Removal of one cerebellar hemisphere is followed by atrophy of the opposite olivary nucleus.