Changes in Anterior and Posterior Hippocampus Differentially Predict Item-Space, Item-Time, and Item-Item Memory Improvement

Relational memory requires the hippocampus, but whether distinct hippocampal mechanisms along the anterior-posterior axis are required for different types of relations is debated. We investigated the contribution of structural changes in hippocampal head, body, and tail subregions to the capacity to remember item-space, item-time, and item-item relations. Memory for each relation and volumes of hippocampal subregions were assessed longitudinally in 171 participants across 3 time points ( M age at T1= 9.45 years; M age at T2= 10.86 years, M age at T3=12.12 years; comprising 393 behavioral assessments and 362 structural scans). Among older children, volumetric growth in: (a) head and body predicted improvements in item-time memory, (b) head predicted improvements in item-item memory; and (c) right tail predicted improvements in item-space memory. The present research establishes that volumetric changes in hippocampal subregions differentially predict changes in different aspects of relational memory, underscoring a division of labor along the hippocampal anterior-posterior axis.