Abstract :
Autumn is upon us, and in the United States, so is football season. The players, who deliver jarring hits to one another that often equal the force of car wrecks, are lionized for the ability to, in the words of an old watch commercial, ¿take a licking and keep on ticking.¿ But concussions are not uncommon, and new research shows that even when players are symptom-free and have passed a battery of cognitive-function tests, their brains may not have completely recovered and may still be vulnerable to further injury.
