The olivary bodies are olive-shaped structures located alongside the descending stem of the human brain. There are two of them, and each can be described as a construction of discreet bundles of nervous tissue called nuclei. Among them, the inferior olivary nucleus is believed to work closely with the parts of the brain that control motor, or muscle coordination.
At its simplest, the human brain is commonly identified as having three main structures: the cerebrum, the cerebellum, and the medulla. Likewise simplified, the larger cerebrum conducts the brain’s higher functions, such as reasoning. The cerebellum controls bodily movement; and the medulla controls the body’s autonomic systems, such as the heart. This is commonly called the brain stem or hind brain, and more precisely called the medulla oblongata.
As a general rule, the brain has bilateral symmetry, a mirrored structure of left and right. The medulla’s external structure includes a large mass called the pons, which among many functions is believed to be the generator of dreams. Beneath it, a pair of thick nerve bundles emerges to eventually become the spinal cord encased in the backbone. Adjacent to them are small, distinctly oval structures about 0.5 inches (1.25cm) long. These are the olivary bodies.
Within them are discernible structures called nuclei, sometimes simply called complexes. The largest of them is collectively referred as the inferior olivary nucleus. Structurally, there appears to be a primary olivary nucleus and two separate accessory nuclei. It looks like a convoluted string of nerve cells. Neurologists who study the structure and function of the brain have traced most of the nerve fibers that exit through an opening called its hilum.
The nerves, called the olivocerebellar tract, climb upward to cross the midline of the brain and terminate in the cerebellum. Among the main functions of the brain’s cerebellum is controlling and coordinating the motor movement of the entire body. The assumption therefore is that the inferior olivary nucleus processes and sends information which is related in some way to this purpose. This is supported by the fact that damage to the inferior olivary nucleus structure may result in significant loss of coordination in either the left or right arms and legs.
Exactly what kind of information the nerves transmit to the cerebellum is under investigation, as of 2011. There are some nerves which climb further into the cerebrum, as well as some which project downward to the spinal cord. Their purposes, as of 2011, are also being investigated.