Disrupted flexible use of context-dependent relational memory in adults following moderate-severe traumatic brain injury

Abstract

Learning associative information and extracting regularities from that remembered information to adaptively meet goals is a hallmark of navigating life. Adaptive goal-directive behavior has been historically attributed to prefrontal functions, and more recently to hippocampal relational memory. Disruptions in either of these systems, both frequently seen in Traumatic Brain Injury (TBI), have far reaching consequences in everyday life. In the current study, we investigate the impact of chronic, moderate-to-severe TBI on both relational memory processes as well as the ability to use regularities or rules extracted from that remembered information to guide behavior via both overt responses and eye-tracking. Individuals with and without TBI completed a context-dependent relational memory task designed to assess both 1) the formation and organization of overlapping relational associations (hippocampal-dependent); and 2) the acquisition and flexible use of learned, context-dependent rules (ventromedial prefrontal-dependent). Behavioral measures revealed that relative to neurotypical matched comparison participants, participants with TBI were significantly impaired on context-dependent relational memory measures, but showed spared memory guided rule-use. Eye-tracking data indicated largely intact information gathering at study for participants with TBI, but impaired flexibility at test leading to poor behavioral outcomes. Critically, these data suggest that relational memory impairment is a significant source of behavioral dysfunction in TBI, which likely contributes to poor outcomes in both laboratory testing and real-life, long-term trajectories following injury. Furthermore, this study highlights the feasibility and strength of incorporating eye-tracking into studies of TBI to gain novel insights into information gathering and use across time.