The primary mood disorders, major depressive disorder (MDD) and bipolar disorder (BD), constitute leading causes of disability on a global scale, yet little is known about their pathogenesis. These conditions are not associated with gross brain pathology or clear animal models for spontaneous recurrent mood episodes.Thus, the development of neuroimagingtechnologies that allowin vivo characterization of anatomy, physiology, and neurochemistryin human subjects withmood disorders has enabled significant advances toward elucidating their pathophysiology. Crucially, the interpretion of abnormalities found using these technologies in mood disorders has depended upon the concomitant delineation of anatomical networks that support emotional behavior.
Early studies identified the amygdala, hippocampus, and other parts of what was termed the “limbic” system as central parts of the emotional brain. Beginning in the 1970’s and 1980’s and continuing through the last 15 years, neuroanatomical techniques based on axonal transport have been applied extensively to the limbic system and prefrontal cortex of monkeys. With these methods, a system has been described that links the medial prefrontal cortex and a few related cortical areas to the amygdala, the ventral striatum and pallidum, the medial thalamus, the hypothalamus, and the periaqueductal gray and other parts of the brainstem. A large body of human data from functional and structural imaging, as well as analysis of lesions and histological material indicates that this system is centrally involved in mood disorders.
High-Resolution MR Imaging of the Human Brainstem In vivo at 7 Tesla
