Project Summary/Abstract While the acute effects of single concussions are beginning to be documented, the long-term effects of recurrent concussions are less well understood. Studies examining the long-term effects of recurrent concussions have found myriad psychological, cognitive, and neurodegenerative consequences months or decades after an athlete?s last concussion. Importantly, studies have differed in terms of which persistent deficits are reported as a function of age of participant/time since injury, however these studies have largely focused on either young adult (under age 30), or ?older adult? (over age 50) samples. The purpose of the current study is to examine whether a ?middle age? (age 30-50) sample of former collegiate football players with and without a history of concussions show similar patterns of cognitive performance, and similar functional and structural connections between resting (default mode) and task-specific (memory) networks during memory binding to a sample of former non-football collegiate athletes. Aim 1 proposes to evaluate memory performance in each sample using a novel multidimensional task of memory binding in which pairs of items vary in the strength of their relationship. It is hypothesized that former collegiate football players with no history of concussions will show similar memory performance to a sample of former collegiate athletes with no football or concussion history, while former football players with a history of concussion will show significantly worse memory performance on this task. Aim 2a will examine functional connectivity between default mode and episodic memory networks from fMRI data collected while participants are performing the memory task. It is hypothesized that former football players with a history of concussions will show less disconnect between the default mode network and a task-relevant memory network during binding than former football players with no history of concussions and former athletes with no history of football or concussions. Further, aim 2b hypothesizes that this lack of disconnect between networks will be directly related to accuracy on the task. Aim 3a will measure structural connectivity between default mode and episodic memory networks, and test its mediation of the relationship between functional connectivity and task performance. It is hypothesized that retired football players with a history of concussions will show compromised structural connectivity between the default mode network and memory networks than former football players with no history of concussions and former athletes with no history of football or concussions. Additionally, aim 3b will assess whether this loss of structural integrity among these networks explains the relationship between functional connectivity and performance on the task (aim 2b). Findings from this project will provide crucial information about the nature of cognitive and neurological impairment as a result of earlier recurrent concussions.