Cardiorespiratory fitness is associated with enhanced hippocampal functional connectivity in healthy young adults.

Consistent associations have been found between higher cardiorespiratory fitness (CRF) and indices of enhanced brain health and function, including behavioral measures of cognition as well as neuroimaging indicators such as regional brain volume. Several studies have reported that higher CRF levels are associated with a larger hippocampus, yet associations between volume and memory or functional connectivity metrics with the hippocampus remain poorly understood. Using a multi-modal framework, we hierarchically examine the association between CRF and hippocampal volume and resting state functional connectivity (rsFC) in younger adults (ages 22-38), as well as the relationship between these imaging markers and memory function. We conducted theoretically driven rsFC and volumetric analyses with seeds in the anterior and posterior portions of the hippocampus, as well as control seeds located in the caudate nucleus. We tested (1) whether hippocampal connectivity with prefrontal cortical regions was associated with CRF in an adult sample much younger than traditionally tested, (2) whether associations between CRF and rsFC remains significant after adjusting for hippocampal volume, and (3) whether volume and rsFC are related to memory performance. We found that higher CRF levels were associated with larger left anterior hippocampal volume, as well as stronger, more positive rsFC of the (bilateral) anterior hippocampus to several regions including the prefrontal cortex. In addition, rsFC accounted for significant variance in CRF, above and beyond hippocampal volume. Higher CRF can thus be independently linked to increased anterior hippocampal volume, as well as stronger hippocampal rsFC in a population much younger than those typically tested. This suggests that CRF may be a critical factor for maintaining multiple aspects of brain health in younger adults, as well as in older adults, the population most often studied in the context of CRF and brain health. This article is protected by copyright. All rights reserved.