Age-related changes in anatomical connectivity of the human hippocampus revealed using quantitative fibre tracking

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

Marshall Dalton¹ (marshall.dalton@sydney.edu.au), Hugo Grenier², Arkiev D'Souza¹, Fernando Calamante¹, Olivier Piguet¹; ¹University of Sydney, Australia, ²University of Marseille, France

Change in memory capacity is a common complaint as people get older. The hippocampus plays a central role in memory and its healthy function is dependent on the integrity of white matter fibres that connect the hippocampus with other brain regions. We still know surprisingly little about age-related changes in structural connectivity of the hippocampus. To address this gap, we combined high-quality structural and DWI data from the Human Connectome Project with cutting-edge fibre-tracking methods to quantitatively characterise structural connectivity between the hippocampus and cortical mantle in two groups of healthy participants; young (26-35 yo; n=10) and older (56-65 yo; n=10). We generated 70 million tracks across the entire brain using dynamic seeding and applied a tailored DWI pipeline that allowed us to identify and isolate tracks (and their density weights) with an endpoint in the hippocampus. Our approach allowed us to quantitatively assess the density of connections between the hippocampus and 180 cortical regions for each participant. Between-group differences in track-density were then assessed using independent samples t-tests. Our preliminary results reveal significantly reduced white matter pathway density between the hippocampus and medial parietal cortex (specifically, area POS1: p<0.05; ~44% reduction) and parahippocampal gyrus (specifically area PHA1: p<0.05; ~39% reduction) in the older participant group. Our novel method provides a powerful new approach to assess age-related changes in white matter pathway density in the human brain in vivo. Our results provide key contributions to ongoing efforts to understand age-related changes to hippocampal dependent memory systems in the human brain.

Topic Area: LONG-TERM MEMORY: Development & aging