mcallister of the indiana university scoostles medicine, dawn comstock of the university of colorado anschutz and, once again, dr. eric kandel. he is, as you know, a noble laureate, bureau of of columbia university and howard hughes medical investigator. i am pleased to have them here at this table. tell me about concussions among young people. >> sports-induced trauma, this has emerged as one of the major health issues of our time. why is that so? let me put this in a bit of a perspective. there is a general consensus that team sports is extremely advantageous for young people. 50 million americans participated in group sports, in athletic competition. and this is beneficial in two ways. athletic and social. from the athletic point of view, they learn early on that almost daily exercise is good for one, and many of them are likely to carry this forward for the rest of their life, ensuring them a healthier life span than they would otherwise. in additiono the physical values, there are also social values that come with it. one learns from team sports a sense of honesty, fair play, team work.