can we go on to dr. mckee? >> data for the invitation to testify today on sports concussions and their consequences. i'm a professor of neurology at pathology at the boss in the university school of medicine, and i direct the neurology at the neurologyv.a. irector for another department. mild traumatic brain injury is a temporary very state under logic to function resulting from forces on the brain, acceleration and deceleration, collateral, and rotational forces. sub concussion is caused by the same type of forces, but the forces are milder and the symptoms are produced. in all of these conditions, concussion or sub concussion, the brain looks normal after the injury and there's no detectable damage on routine imaging, which is why these eight injuries are considered invisible. the acceleration, deceleration, our official forces caused the brain to move rapidly within the skull and brain which is firm, but gelatinous, is stretched and deformed by these forces. as the brain is deformed, there's also stretch and

and dr. mckee talked a little bit about anti-concussion mouth guards. have you seen ads such as this one for a mouth guard that is sold for use by kids 11 years and under? and you can see the poster here in the background. this one was purchased last month. the product packaging states this mouth guard reduces the risk of concussions, and it creates brain safety space. given your firsthand knowledge of the dangers of repetitive brain trauma, are you troubled by this type of marketing for youth sports equipment? do you think young athletes who have already had a concussion might be particularly susceptible to advertising claims for so-called anti- concussion devices? >> well, there is no clear evidence that any mouth guard or a chain guard reduces the the the rage or severity of concussion. so i would have a great objection to this claim. the only thing that i am aware of that mouth guards and chin guard stood there reduce oral, official, and dental injuries. but the nature of concussions would not be improved with the use of mouth guards. >> i know you

dr. ann mickie, a professor of pathology -- ann mckee, a professor of biology. i am also co-director for the center of dramatic encephalopathy. i am not speaking on behalf department of veterans affairs. mild brain injury, or concussion, is a temporary state of neurological dysfunction resulting from forces on the brain, acceleration, deceleration collateral and rotational forces. some of concussion is caused by these same forces, -- sub- concussion is caused by the same forces, but symptoms are milder. in all of these cases, the brain looks normal after the injury and there is no detectable damage on routine euro imaging, such as acy thank fdot -- such as a ct scan or mri. as the brain as a whole is stretched or deformed by these forces, there is also stretching on the support cells within the brain. the brain abnormalities associated with a concussion occur at the molecular and metabolic levels. if an athlete returns to play before the symptoms result, the athlete risks of developing post-concussion syndrome or cysts that are a rare, but often fatal, condition