Inferior olive (or olivary) nucleus

The largest nucleus in the brain stem (in the lower part of the medulla oblongata), with neurons that project to the contralateral cerebellar cortex and deep cerebellar nuclei via the inferior cerebellar peduncle (or restiform body).  Upon reaching the cerebellum, the projections end on climbing fibers (in fact, the nucleus is the only source of climbing fibers).  Little is understood about the function(s) of the nucleus, but with its intimate connections with the cerebellum it is likely to be involved in movement coordination and motor learning.  It is known, however, that lesions to the nucleus are associated with decrements in rather specific actions (e.g., hitting a target by means of throwing an object).    

See Brain stem, Cerebellum (anatomy), Cerebellum (functions), Climbing fibers, Medulla oblongata, Motor control, Motor learning, Movement coordination, Red nucleus