Brain Scans (IMAGE) Purdue University Caption Brain scans show differences among high school football players in a two-year study that suggests concussions are likely caused by many hits over time and not from a single blow to the head, as commonly believed. Credit Purdue University image/Thomas Talavage Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.