an olive-shaped mass of gray matter in the medulla oblongata, comprised of two sets of nuclei: the inferior olivary complex (or inferior olivary nucleus or inferior olive), which lies on the ventral part of the medulla oblongata and is believed to be involved in motor control; and the superior olivary complex (or superior olivary nucleus or superior olive), which lies in the pons just above the inferior olivary complex and plays a significant role in the perception and localization of sound. Also called olivary body; olivary complex.