Hippocampus is a complex structure with broad implications for various cognitive processes, including memory. Previous studies have reported overlapping anatomical and functional organizations in the hippocampus, reflecting the medial-lateral as well as the longitudinal axes. However, age-related alterations in these organizations and their links to behavioral and molecular phenotypes are unclear. Using a connectopic mapping approach on a resting-state fMRI data from 180 participants (20-79 years), we identified two modes of long-axis organization reflecting a gradual anterior-posterior variations as well as the unimodal-transmodal microscale cortical organization. Both gradients were age-sensitive such that less distinctive transition in functional connectivity (FC) along their axes was observed. Critically, older individuals with youth-like gradient organizations exhibited more efficient memory processing compared to age-matched counterparts with less distinctive FC transition. Moreover, the topological organization of the unimodal-trasmodal gradients was associated with underlying distribution of postsynaptic dopamine D1 receptor, suggesting a shared organizational principle within the hippocampus. Finally, youth-like functional gradient profile was concomitant with youth-like distribution of hippocampal D1 receptor in older age. Taken together, our results identify distinct overlapping modes of cortical FC within the hippocampus and highlight the importance of maintained hippocampus organization in older age.

Authors:
Alireza Salami, Karolinska Institute and Umea University, Sweden
Kristin Nordin, Karolinska Institute, Sweden
Robin Pedersen, Umeå University, Sweden
Jarkko Johansson, Umeå University, Sweden

About the Presenter(s)
Professor Alireza Salami is a University Associate Professor/Senior Lecturer at Karolinska Institute and Umea University in Sweden

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