Functional and molecular brainstem imaging.

The brainstem connects the cerebrum, cerebellum, and spinal cord and includes several nuclei that produce key neurotransmitters important for the modulation of behavior and cognition. Since the 16th century, humans have tried to understand the importance of the brainstem in health and disease. The development of modern neuroimaging methods, using functional magnetic resonance imaging or positron emission tomography, has ushered in an era of understanding function and molecular changes in the brainstem in many neurologic diseases. This chapter discusses the methodologic complexities of imaging the neuromodulatory subcortical nuclei in the brainstem. Furthermore, we discuss the current state-of-the-art clinical applications using these techniques for early detection, differential diagnostics, monitoring of disease and intervention, and drug development, highlighting future perspectives for the field.