Development of human hippocampal subfield microstructure related to associative inference.

The hippocampus is a complex brain structure composed of subfields that each have distinct cellular organizations. While the volume of hippocampal subfields displays age-related changes that have been associated with inference and memory functions, the degree to which the cellular organization within each subfield is related to these functions throughout development is not well understood. We employed an explicit model testing approach to characterize the development of tissue microstructure and its relationship to performance on two inference tasks, one that required memory (memory-based inference) and one that could be completed based on perceptually available information (perception-based inference). We found that each subfield had a unique developmental trajectory in terms of its cellular organization. While the SUB displayed a linear trajectory, DG, CA1, and CA2/3 subfields displayed non-linear trajectories that interacted with sex in CA2/3. We found that the DG was related to memory-based inference performance and that the SUB, a subfield outside of the hippocampus proper, was related to perception-based inference; neither relationship interacted with age. Results suggest that cellular organization within hippocampal subfields undergo distinct developmental trajectories that may underlie changes in inference and memory performance throughout development.