The unifying theme of Dr. Gregory Crosby’s research is that general anesthesia and surgery change the brain. Initially he focused on the metabolic and blood flow effects of general anesthetics on the brain and spinal cord; later, he investigated the impact of general anesthesia on the processing of noxious stimuli; and for the past 15+ years has focused on the impact of anesthesia and surgery on the vulnerable aged brain. Crosby and colleagues Drs. Deborah Culley (BWH) and Zhongcong Xie (MGH) were the first to demonstrate that an uncomplicated general anesthetic without surgery produces long-lasting learning impairment in old but not young rodents and then in subsequent in vitro and in vivo experiments showed that anesthesia and surgery cause neuronal apoptosis, alter processing of amyloid precursor protein, and increase production, accumulation, and aggregation of amyloid β, a protein implicated in the pathogenesis of Alzheimer’s disease. Dr. Crosby has been funded by the NIH almost continuously for 38 years including currently for preclinical work on microglia as mediators of surgery-induced neuroinflammation and human studies on circulating extracellular vesicles as potential biomarkers of anesthesia and surgery-induced cerebral injury in geriatric patients.