A growing body of research shows that children who suffer severe neglect and social isolation have cognitive and social impairments as adults. A study from Boston Children's Hospital shows, for the first time, how these functional impairments arise: Social isolation during early life prevents the cells that make up the brain's white matter from maturing and producing the right amount of myelin, the fatty "insulation" on nerve fibers that helps them transmit long-distance messages within the brain.