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 in studies of morphology and reduced network response in studies of functional connectomics. 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. Additionally, the interactive effects of aging and traumatic brain injury (TBI) are associated with increased risk for neurodegeneration and episodic memory impairments. However, there is a gap in the literature examining episodic memory and hippocampal-subcortical resting state connectivity differences related to aging with and without TBI. The current work aims to investigate episodic memory differences 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 differences at rest. We demonstrate a positive relationship between default mode and frontoparietal network connectivity and memory performance differentially between those aging with and without moderate-severe TBI (msTBI). 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 is generally reliable across other connections.