LAS VEGAS (AP) -- It's a question that has puzzled doctors since the days Joe Louis ruled the heavyweight division.
Why do some fighters suffer brain damage from punches taken in the ring while others can get hit in the head for years and show few effects?
Part of the puzzle could be answered in a study of boxers now being conducted in Las Vegas.
Some 148 current boxers and MMA fighters have already taken their first set of tests for the study, funded mostly by hotel magnate Kirk Kerkorian and conducted at the Cleveland Clinic's new Lou Ruvo Center for Brain Health, which is located in downtown Las Vegas.
Researchers hope to eventually enroll more than 600 fighters in what is hoped to be at least a four-year study of their brains.