Hippocampal network connectivity and episodic memory in individuals aging with traumatic brain injury

Aging is associated with marked declines in episodic memory corresponding with decreased volume and activation in the hippocampus. Furthermore, recent research has demonstrated that reductions in resting state network connectivity are related to declines in episodic memory, specifically in the default mode and frontoparietal cortical networks. In addition to age-related episodic memory decline, traumatic brain injury (TBI) is also associated with worsened memory performance alongside hyperconnectivity in cortical networks. However, there is a gap in the literature examining resting state connectivity changes related to aging with TBI in subcortical and hippocampal regions that are important to episodic memory, such as the hippocampus. The current work aims to investigate episodic memory changes between older adults with TBI (N=45) and older adults with no history of TBI (N=28) and how that relates to hippocampal-subcortical network changes at rest. We demonstrate a positive relationship between default mode and frontoparietal network connectivity and memory performance differentially between those aging with and without TBI. Additionally, we demonstrate that reliability in the strength of resting state functional connectivity between parcellations is weakest among connections to the hippocampus compared to other cortical connections, but generally reliable across other connections.