Hypoglycemia-associated autonomic failure (HAAF) is a serious complication that develops as a consequence of insulin therapy and recurrent hypoglycemia, primarily in people with type 1 diabetes, but increasingly in type 2. HAAF attenuates epinephrine and compromised glucagon counterregulatory responses (CRRs), and develop 'hypoglycemic unawareness'. It can be fatal. All the mechanisms currently proposed for HAAF involve the brain. This means that understanding the organization of the brain network that controls glycemia is a fundamental objective for understanding the causes of HAAF. However a major impediment is the far from complete picture of all the components of this network together with its detailed connectome. The goal of this proposal is to determine where information from diverse glucosensory sites distributes within the brain and where potential integrative sites are located. It will use state-of-the-art neurotropic viral tracing techniques, functional Fos mapping, and a novel neuroinfomatic tool (Axiome) developed at USC that is designed to extract network interactions from complex neuroanatomical datasets. Three specific aims will explore structural and functional interactions between the motor systems that drive endocrine CRRs from the adrenal medulla and pancreas, and key glucosensing regions that are located inside and outside the blood brain barrier: the ventromedial hypothalamus (VMH), the area postrema, and the wall of the hepatic portal vein. Of particular importance for HAAF is that two of these regions are important because of their contributions to the endocrine CRRs that develop from rapid- (VMH) and slow-onset (hepatic portal vein) hypoglycemia. Slow-onset hypoglycemia is thought to be most prevalent in iatrogenic insulin-induced hypoglycemia in diabetes. These new findings will combine these connectional and functional results in a totally novel way thereby identifying major network components and significantly improving our understanding of how the brain controls glycemic counterregulation and how this breaks down in HAAF.