Mn neurotoxicity will be investigated by longitudinal assessments of cognitive (executive functioning battery), neurodevelopmental (Bayley III Scales of Infant Development), and psychophysiological (event-related potential) measures and will be correlated with brain deposition of Mn using the technique of magnetic resonance (MR) relaxometry in a vulnerable population of infants receiving Mn-supplemented PN and age-matched controls. This proposal addresses a clinically relevant and unexplored link between nutritional practices, brain Mn deposition and neurodevelopmental sequelae in an at-risk population of infants and young children utilizing state-of-the-art magnetic resonance imaging (MRI) technology and neurodevelopmental assessment techniques. The potential for increased brain Mn accumulation in infants, and by inference, the potential health risks associated with elevated brain Mn burden, represents crucial, unexplored issues of exposure and susceptibility. The potential contribution of Mn toxicity to the poor outcomes of infants dependent for an extended time on PN has not been fully acknowledged or studied. Improved understanding of the relationships between Mn exposure and developmental outcomes will undoubtedly lead to altered clinical practices and more careful monitoring of Mn intake and blood and/or brain Mn levels in high risk infants. Our studies will also contribute to an improved understanding of the value of non-invasive MR imaging in the monitoring of pediatric patients on PN.