Hippocampal subfield-specific alterations in post-stroke dementia with subcortical lesion

The structural and functional characteristics of hippocampal subfields have been extensively studied in dementia, with findings indicating stronger associations with cognitive performance than those observed in the whole hippocampus (HP). However, the impact of post-stroke dementia (PSD) on the structural and functional connectivity between hippocampal subfields and cortical regions remains unclear. The objective of this study is to examine alterations in the functional and structural connectivity between hippocampal subfields and cortical regions in PSD. We collected resting-state functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) data from 24 PSD patients, 36 post-stroke non-demented (PSND) patients, and 21 normal controls (NC). These data were used to estimate fractional amplitude of low-frequency fluctuations (fALFF), fractional anisotropy (FA), and diffusivity maps in the hippocampal subfields. Additionally, we constructed functional and structural connectivity matrices between hippocampal subfields and cortical regions for each participant, highlighting group-specific connectivity alterations. Statistical analyses were conducted using a linear mixed model to compare group differences and assess the relationship between MRI measures and clinical evaluations. Our results revealed distinct PSD-related changes in functional connectivity, particularly with the temporal-occipital cortex, within hippocampal subfields compared to the whole HP. Notably, different subfields contributed differently to connectivity changes within the entire HP. Furthermore, we identified positive correlations between diffusivity in the bilateral hippocampal tails and illness duration in PSND patients, which were not observed in PSD. These findings highlight the significant impact of PSD on hippocampal subfields, with subfield analysis offering new insights into the underlying mechanisms of PSD.