a large aggregate of small densely packed nerve cells consisting of medial and dorsal accessory olivary nuclei and a principal olivary nucleus that is arranged in folded laminae shaped like a purse with the opening (hilum) directed medially. It corresponds in position to the oliva, projects to all parts of the contralateral half of the cerebellar cortex by way of the olivocerebellar tract, and is the only source of cerebellar climbing fibers. Its afferent connections include fibers from the spinal cord, dentate nucleus, and motor cortex, but its major input appears to be the central tegmental tract originating from multiple nuclei at midbrain levels. SYN: nucleus olivaris inferior.