Manganese (Mn) is an essential metal required for normal growth and development. However, exposure to high Mn levels can be toxic to the brain. The objectives of this project are to identify neonatal and young pediatric populations that are at increased risk of excessive brain Mn deposition and altered cognitive and motor development based on their dietary parenteral Mn exposure, and to make sound and evidence-based recommendations for appropriate Mn supplementation and monitoring of infants and young children receiving parenteral nutrition (PN). Our studies are designed to test the hypotheses that, compared with unexposed age-matched controls, infants and young children receiving prolonged Mn-supplemented PN will have increased deposition of Mn in their brains and lower scores on neurodevelopmental, cognitive and psychophysiological assessments.