What Is a Concussion? 5 removed the fake brain. He saw extensive damage to it. He described the loca- tion of the damage sustained by his gelatin brain and published his findings in a medical journal, the Lancet . This led him as well as other scientists and physicians to believe that “spinning” a brain caused more of a problem than simply accelerating it in a straight line. However, the debate over whether rotational acceleration of the brain was more harmful than linear acceleration continued for some time. More than 30 years after Holburn’s experiment, the debate was taken up again. In order to better determine the effects of linear and rotational accel- eration on the brain, two scientists, named Ommaya and Gennarelli, took the experiments one step further. They produced concussion without ever striking the brain. They separated 24 monkeys in two groups. The monkeys were each placed in a helmet, snugly affixed to the monkeys’ heads. For 12 of the monkeys, they used a mechanical device, to move the helmet rapidly forward, in a straight line, one inch. All of the monkeys who underwent this linear acceleration of one inch appeared well afterward. They did not appear confused, off-balance, or dazed. They did not lose consciousness. The remaining 12 monkeys were placed in helmets as well. But this time, the helmets were spun or rotated over an arc of one inch, using the exact same amount of force. This rapid rotational acceleration resulted in all 12 monkeys being immediately knocked unconscious. Note, there was no blow to the brain the animals were not struck in any way. Their heads were simply accelerated either in a purely linear or purely rotational direction. Thus, this experiment confirmed that it was not simply the rapid movement or acceleration of the brain that produced the concussion, but rather the spinning or “rotational acceleration,” which resulted in concussive brain injury. More recently, video analysis of concussions and studies performed on players from the National Football League revealed that most concussive inju- ries are caused when a player is struck on the side of the helmet or face mask. In fact, the facemask often acts as fulcrum, causing a more rapid acceleration of the brain than blows to the shell of the helmet. Such a blow, results in a rotational acceleration of the brain, or spinning of the brain, in the opposite direction of the blow. In many ways, a blow to the facemask and a blow to the chin result in a similar action on the brain. Let us consider for a moment a boxer striking one of his opponents. If a powerful blow is landed in the middle of the head, say just above the left ear, it may cause a lateral bending of the neck. The neck may be stretched, such that the boxer’s head bends down toward the right, with the right ear moving down toward the right shoulder. If, however, the boxer throwing the punch manages to land his blow on the chin, side of the face, or side of his opponent’s forehead, the head of the boxer struck will spin very rapidly toward the right. Thus, the athlete struck more toward the front of the head is more likely to sustain a concussion than the athlete struck in the middle of the head. Those of you seeking confirmation for this need merely watch ultimate fighting championships greatest knockouts, YouTube videos
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