Our studies of the brain stem are related primarily to the development of the medulla oblongata, the pons, and the mesencephalon.

The brain stem is the regulatory seat of a myriad of vital body functions that involve most of the organ systems of the body. The list of vital functions is long and encompasses many major health problems, including hypertension, respiratory disorders, mood disorders such as depression and anxiety, sleep disorders, gastrointestinal disorders, vestibular disorders, disorders of motor coordination, and pain. These functions are predominantly autonomic (without conscious control) and arise from a structurally intricate system of reflex arcs and neuronal networks. That they are in most cases fully operative at birth indicates that they must be established by robust and highly conserved developmental mechanisms. Indeed, studies of brainstem development during the past decade have shown that the proper anatomical and functional patterning of neuronal assemblies in the brain stem is dependent on the proper spatio-temporal expression of specific genes. In other words, normal brainstem patterning arises from a stereotyped and determinate genetic program.

Although the intricacy of genetic regulation underlying brainstem development is widely appreciated among developmental neuroscientists, it is as yet poorly described and understood. On the other hand, a growing number of genes has been identified whose expression can be linked to specific brainstem regions and neuron populations. The task at hand therefore is to obtain a comprehensive description relating genes to neuron groups, neuronal circuits, and brainstem functions, and to test these relationships by gene manipulation to determine which genes play critical roles in constructing the brain stem.

Armed with this information, it should be possible in the future to better diagnose and predict autonomic disorders that have a genetic basis. It may also be possible to characterize brainstem tumors (some of which are among the most common tumors in children) more completely. In a longer perspective, knowledge about how specific genes contribute to the production of specific neuron types may facilitate the use of stem cell technology to treat disorders that arise from the degeneration or developmental lack of brainstem neurons.

For further reading, see these and related articles in Encyclopedia of the Human Brain (2002), Editor-in-chief: Dr. V. S. Ramachandran, Academic Press, ISBN 0122272102:

W.W. Blessing, Brainstem
J.C. Glover, Hindbrain.
D.L. Oliver and D. Waitzman, Midbrain
A.B. Butler, Cranial Nerves.

* A grammatical note: “brain stem” as noun is written as two separate words; as an adjective in one word (brainstem).

Figure 1. The human brain seen from the midline. The brain stem lies at the core of the brain, connecting it to the spinal cord. It is organized into vertically stacked divisions, including (from the bottom up) the medulla, pons, and midbrain. The cerebellum is attached to the pons. The diencephalon and cerebrum are the next higher levels above the midbrain. From the book “Neuroanatomy” (1989), by J.H. Martin; Appleton and Lange.

Figure 2. The human brainstem seen from the front. The 3 major divisions (medulla, pons, midbrain) are shown, as well as the cranial nerves, which bring information from the body to the brain stem and carry information from the brain stem to the body. From the book “Principles of Neuroscience” (1991), edited by E. Kandel, J.H. Schwartz, and T. M Jessell, 3rd edition; Elsevier.