As Larry Leverenz, Ph.D, ATC, a co-author
of the groundbreaking 2010 study (4) that was the first to identify such athletes noted, because such athletes have not suffered
damage to areas
of the brain associated with language and auditory processing, they are unlikely to exhibit clinical
signs of head injury (such as headache or dizziness), or show impairment on sideline assessment for concussion, all
of which test for verbal, not
visual memory.
Although scientists have long suspected that RHI caused brain
damage, especially in boxers, a 2010 study
of high school football players by researchers at Purdue University [1,13] was the first to identify a completely unexpected and previously unknown category
of players who, though they displayed no clinically - observable
signs of concussion, were found to have measurable impairment
of neurocognitive function (primarily
visual working memory) on computerized neurocognitive tests, as well as altered activation in neurophysiologic function on sophisticated brain imaging tests (fMRI).