dr. susan margalise at the university of pennsylvania. new research that was done by a doctor at harvard shows that for mild traumatic brain injury we see there are disabilities that emerge that might not have been thought to be the case and here there's a slight difference. it's the teenagers who have more disability from the same level of mild traumatic brain injury. i think that this really shows that we're just beginning to truly understand the biomechanics of brains, the biology of what happens in the event of injury and this knowledge and this furthering of our understanding of our scientific foundation is going to help us to come up with better helmets, better prevention strategies and better therapies and i hope better recovery. >> you mention the short-term and long-term effects of brain injury in children. can you have long-term effects without noticing any short-term injury? >> i think that you usually will see something early on but there's some subtle differences. children are continuing to develop as we go forward. i often t