What happens to the brain after a concussion? It's a little hard to answer because, as you know, people don't die from a concussion, so we don't have necessarily brain tissue to analyze. But there are many papers that speculate that there's a mismatch between the oxygen or the fuel supply to the brain after it is injured. You can have everything from cell death of the neurons--the brain cells-- to just malfunction of the brain cells. The connections between the brain cells don't work as well. This is our working hypothesis. That's why it seems transient. It appears reversible. And then it may explain why some people get better faster than others, and others have long-term consequences. We think we know what's happening, but again, because people don't--thank God-- don't expire right away from this, we're just guessing. One of the biggest problems we deal with is, we don't have a quick test to talk about concussion. A concussion just means simply, the violent shaking of the brain. It would be nice to get a blood test that says, oh, you've had a concussion, you haven't. Right now, we make the diagnosis of concussion based on the symptoms. If we witness somebody's head hitting another head, hitting the ground, hitting an object-- as we see in sports or in the military-- or a blast, a wave comes and hits your head, we call that a concussion. The symptoms that people get from this are headaches, cognitive problems, malaise-- a whole host of symptoms. So, there is no good blood test. Similarly, there is no blood test for chronic traumatic encephalopathy. The thought is that there is an increase in something called beta-tau protein or beta-tauopathy in these brains. Having said that, this is a rapidly evolving field. In just the last few months, there was an article out which showed that beta-tau is also found in normal brains. So, now it's very confusing. Is this different in traumatic brains versus the controlled, normal brains? We don't know the answer. I think we're going to hear a lot more interesting results. As you know, Boston University received a grant from the NFL of about a million dollars to study this subject. They're doing autopsies on athletes, and there's a brain bank there where athletes can donate their brains-- or they can donate them to the NFL-- and they will have other neuropathologists who look at autopsied brains to determine what the changes are. There are a lot more questions than there are answers. We don't have a good blood test. We don't even have a good test other than a standard neurologic exam. And interesting that you asked because the NFL just came out this year-- our team of doctors that consults for the NFL-- a team of academicians basically came up with an NFL sidelines exam to standardize the exams that are performed on the players before the season starts and then once they are concussed, so that we can make a good determination on the sidelines. Did this player have a concussion, and he has to be removed from the game, or did he not have a concussion, and he can go back to play.