fluent in English, and a history of multiple concussions , low exposures , or no concussions (Control group ). Determination of concussion exposure will be determined as follows: Previous concussion will be based on the player's recall of injury and defined as "an injury resulting from a blow to the head that caused an alteration in mental status and one or more of the following symptoms: headache, nausea, vomiting, dizziness/balance problems, fatigue, trouble sleeping, drowsiness, sensitivity to light or noise, blurred vision, difficulty remembering, and difficulty concentrating.