dr. margulies, the bio mechanics, not every injury are the same in how they affect different brain regions and that may play a role. very interesting work suggests genetic factors may impact this. so you and i might differ in terms of the genes that we have for getting better or not getting better after a concussion. >> rose: let me turn to walter and talk about how the young brain is different. >> right, charlie, so i think our brains are always developing, even in adult life. new connections are being made. this is much more dramatic during childhood. the the changes occurring in the young brain are so dynamic. the energy that the brain uses peaks in late childhood and adolescence. the blood flow peaks in late childhood and adolescence. and as eric said, the brain is a massive computer where the connections are just tremendously exuberant right at the beginning. then it's molded over time by activity and experience to make us who we are. that molding period, as eric mentioned, is because connections that are not useful are taken away, the sna synaptic bruining and that's occurring at a p