Preliminary study on changes in volume and functional connectivity of hippocampal subregions in patients with diabetic retinopathy.

The aim of this study is to investigate the disparities in volumes of hippocampal subfields and alterations in whole-brain functional connectivity among individuals diagnosed with diabetic retinopathy (DR). This study comprised a total of 32 diabetic patients with retinopathy (DR group, n = 32) and 38 healthy adults (HC group, n = 38), who underwent psychological cognitive testing along with structural and functional magnetic resonance imaging. The FreeSurfer software was utilized for the extraction and computation of hippocampal subfield volumes, as well as the overall volumes of the left and right hippocampus. The volumetric comparisons were conducted by employing independent sample t-tests in SPSS 26.0. The functional connectivity comparisons were subjected to statistical analysis using the Matlab software. Age, education level and grnder were used as control variables, and partial correlation analysis was performed to investigate the relationship between differences in volume and functional connectivity values with psychological cognitive test results and clinical indicators. The volume of the left hippocampal tail and fissure, as well as the right hippocampal C3, C4 and fissure regions in the DR patient group, exhibited significant differences compared to the HC group (P < 0.05, FDR < 0.05). Regions of interest were identified based on the segmented volume differences, and compared to the HC group, enhanced connectivity was observed between the left hippocampal tail and the left caudate nucleus (MNI: x,y, z=-6, 12, 9) and the right caudate nucleus (MNI: x,y, z = 9, 12, 12) in DR patients. Additionally, reduced connectivity was observed between the left hippocampal fissure and the right precentral gyrus (MNI: x, y, z = 57, 0, 45) and the right supplementary motor area (MNI: x, y, z = 9, 3, 60). Partial correlation analysis, with age, education level, and gender as covariates, showed no significant associations between the imaging changes and clinical indicators or cognitive scores. The alterations in hippocampal volume and function observed in patients with DR may potentially underlie their cognitive impairment and sensorimotor deficits, thus suggesting a plausible neuropathological mechanism.