Examining the impact of fornix and cingulum microstructure in memory for naturalistic events

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

Xianze Meng¹ (marcus.meng@mail.utoronto.ca), Charan Ranganath², Alexander Barnett³; ¹York University, University of Toronto, ²University of California, Davis, ³University of Toronto

Previous work has shown that the functional connectivity (FC) between the hippocampus (HC) and the posterior medial network (PMN) during event offset is associated with subsequent recall success and retention of details. This study focused on the white matter pathways between HC and PMN (the posterior fornix and cingulum) and sought to investigate the relationship between white matter microstructure and memory performance. We hypothesized that microstructure properties within the posterior fornix and cingulum would relate to functional connectivity (FC) between HC and PMN and predict recall performance. Participants were scanned using fMRI as they encoded two 15-minute movies and verbally recalled them immediately or after a 2-day delay. We additionally collected diffusion-weighted MRI for each participant. The verbal recall was transcribed and scored using published scoring methods. We extracted white matter microstructure metrics (fractional anisotropy, axial and radial diffusivity) for the fornix and cingulum from individually delineated probabilistic tractography. We performed a principal component analysis to obtain microstructural scores for each participant. The whole-movie HC-PMN FC was calculated using Pearson’s correlation. Using linear models, we modelled the relationship between microstructure versus FC and microstructure versus memory. We found a positive relationship between cingulum microstructure and memory, in which retention of central details was associated with high cingulum fractional anisotropy and low axial and radial diffusivity. The fornix-recall relationship was similar but lacked significance. The results suggest that the cingulum may play an important role in supporting the long-term maintenance of episodic memory.

Topic Area: LONG-TERM MEMORY: Episodic