Premature babies have a high risk of neurodevelopmental disability and there is no effective treatment. Although multiple factors are involved, disability is closely linked to infection and inflammation around the time of birth. In this study, we will first test whether exposure to a clinically silent dose of a key part of bacterial cell walls for just 5 days will impair growth of the branches (dendrites) that connect brain cells together, and so reduce the growth and function of the brain. We will then test whether blocking one of the key inflammatory pathways in the brain will help restore normal maturation of brain cells and brain activity and determine the window of opportunity for treatment. This new knowledge will help us understand how cognitive deficits develop in preterm infants and provide a new way of protecting normal brain development.