SUMMARY Childhood trauma exposure constitutes a major risk factor for subsequent psychopathology, including depression, posttraumatic stress disorder, substance abuse, personality disorders, and schizophrenia. Violence exposure in low-income, urban populations can occur early in life, increasing risk for trauma exposure in children living in inner-city areas. While it is shown that early adverse experiences affect brain activation and connectivity as well as fear physiology during development in children, the mechanisms of these effects on the brain are not clearly understood. Very few studies have captured the effects of ongoing trauma during development, as most are based on retrospective data. The proposed longitudinal study is well-positioned to address this gap in knowledge given our recruitment from a high trauma risk population. The proposed research will combine neuroimaging and fear physiology methods to examine critical periods for trauma-related correlates of brain development. Recruitment of male and female children will allow for exploratory analyses of sex differences during development. Retrospective research on trauma exposure and neural development suggest that ages 9 through 11 represent particularly sensitive periods for fear-relevant neurobiology. In order to target this critical period, 9-year-old children will be recruited from the Grady Trauma Project in inner-city Atlanta, composed primarily of low-income, African American families and followed prospectively for two years. Trauma exposure and startle will be assessed every six months between ages 9 and 11, in order to assess the critical period for trauma exposure. Brain structure and function will be assessed every year, at years 9, 10, and 11. In our previous studies, we have found that the degree of trauma exposure significantly increases between 9 and 11 years of age. The unique prospective longitudinal design will allow for analysis of the effects of both pre-existing trauma and new trauma exposure on the neurobiological phenotypes.