Brian Johnson, Thomas Neuberger, Michael Gay, Mark Hallett, Semyon Slobounov

Although less severe than a full blown concussive episode, subconcuussive impacts happen much more frequent and current research has suggested this form of head trauma may have an accumulative effect and lead to neurological impairment later in life. To investigate the acute effects that subconcussive head trauma may have on the default mode network of the brain resting state functional magnetic resonance was performed. Twenty-four current collegiate rugby players were recruited and all subjects underwent initial scanning twenty-four hours prior to a scheduled full contact game to provide a baseline. Follow-up scanning of the rugby players happened within twenty-four hours following that game to assess acute effects from subconcussive head trauma. Differences between pregame and postgame scans showed both increased connectivity from the left supramarginal gyrus to bilateral orbitofrontal cortex and decreased connectivity from the retrosplenial cortex and dorsal posterior cingulate cortex. To assess whether or not a history of previous concussion may lead to a differential response following subconcussive impacts, subjects were further divided into two subgroups based upon history of previous concussion. Individuals with a prior history of concussion exhibited only decreased functional connectivity following exposure to subconcussive head trauma, while those with no history showed increased connectivity. Even acute exposure to subconcussive head trauma demonstrates the ability to alter functional connectivity and there is possible evidence of a differential response in the brain for those with and without a history of concussion.