Poster Session 04 Program Schedule
02/15/2024
12:00 pm - 01:15 pm
Room: Shubert Complex (Posters 1-60)
Poster Session 04: Neuroimaging | Neurostimulation/Neuromodulation | Teleneuropsychology/Technology
Final Abstract #28
Age-Related Changes in Anatomical Connectivity of the Human Hippocampus: Insights Using Quantitative Fibre-Tracking
Marshall Dalton, University of Sydney, Sydney, Australia
Hugo Grenier, University of Marseille, Marseille, France
Olivier Piguet, University of Sydney, Sydney, Australia
Category: Aging
Keyword 1: aging (normal)
Keyword 2: hippocampus
Keyword 3: neuroimaging: structural connectivity
Objective:
Change in memory capacity is a common complaint as people get older. The hippocampus plays a central role in memory during encoding and retrieval processes. Memory function, however, is also dependent on the integrity of white matter fibres that connect the hippocampus with a range of anterior and posterior cortical brain regions. Although, age-related changes in structural integrity of the hippocampus have been previously documented, we still know surprisingly little about the age-related changes in structural connectivity between the hippocampus and other brains regions. Our primary objective was to apply novel diffusion weighted imaging methods to map the anatomical connectivity of the human hippocampus and assess how these connections change with age. We investigated changes between young and middle-aged participants, a comparatively understudied age group.
Participants and Methods:
We combined high-quality structural and diffusion weighted imaging 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 (26-35yo; n=10) and older (56-65yo; n=10). First, to ensure anatomical accuracy, the hippocampus was manually segmented for each participant on the T1-weighted structural image. We then generated 70 million tracks across the entire brain using dynamic seeding. We then applied a tailored pipeline that allowed tracks to enter the manually segmented hippocampus rather than terminate at the hippocampal grey matter/white matter boundary. An additional 10 million tracks seeding from the hippocampus were generated, which were combined with the 70 million whole-brain tracks. This approach allowed us to quantitatively assess the density of each white matter track. Tracks (and their density weights) that had an endpoint in the hippocampus were identified and isolated. We then generated a connectome using the identified tracks and weights connecting the hippocampus with the cortical mantle. This enabled us to measure 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.
Results:
Our method was effective in identifying significant between-group differences in track-density between the hippocampus and specific regions of the cortical mantle. Results of statistical analysis revealed significantly reduced white matter pathway density between the hippocampus and medial parietal cortex (specifically, area POS1: p < 0.05; ~44% reduction in white matter density) and parahippocampal gyrus (specifically area PHA1: p < 0.05; ~39% reduction in white matter density) in the older participant group.
Conclusions:
Our novel method provides a powerful new approach to assess age-related changes in white matter pathway density in the human brain in vivo. Age-related reductions in white matter pathway density between the hippocampus, medial parietal and parahippocampal cortices may represent a biological basis for age-related memory changes. Our results provide key contributions to ongoing efforts to understand age-related changes to hippocampal dependent memory systems in the human brain.
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