A Comprehensive Study of Hippocampal Subfields Volumes

Abstract

Introduction: Recently, there has been renewed interest in the studies of the hippocampal subfields in relation to their structural and functional abnormalities in patients and healthy individuals. We hypothesized that cognitive decline, APOE ε4 and depression, might be associated with the atrophy of the hippocampal subfields volumes. Furthermore, cognitive ability and intelligence could be predicted from the volumes of the hippocampal subfields, together with the influence of APOE ε4. Methodology: Aberdeen Children of the 1950s (ACONF) dataset (254 participants) and Aberdeen STratifying Resilience and Depression Longitudinally (STRADL) dataset (527 participants) were analyzed. Brain MR images were acquired for each participant to evaluate the volumetric data using FreeSurfer v 6.0 software for image processing and segmentation. Additionally, six cognitive tests were collected to examine different abilities such as memory and processing speed of information. The intelligence was measured as an IQ like-score extracted from six cognitive tests. A face-to-face questionnaire was held to assess depression using the Quick Inventory of Depressive Symptomology (QIDS). Moreover, APOE ε4 allele was extracted by genotyping blood and saliva samples. These data were statistically analyzed using Statistical Package for the Social Sciences (SPSS) software. Results: From the correlation analyses, right hippocampus and right CA1 volumes showed a significant positive association with IQ like-score. Additionally, APOE ε4 carriers revealed a significant reduction in right CA4 and right GC-ML-DG volumes. Depression was found to be more sensitive to GC-ML-DG. The regression analysis showed that the hippocampus and APOE ε4 significantly predict the processing speed of information and IQ like-score, where APOE ε4, right CA1, right GC-ML-DG and right CA4 contribute significantly to the prediction of IQ like-score. Conclusion: Particular hippocampal subfields reported significant associations with IQ like-score, depression and APOE ε4. Most of the significant results were found in the right hippocampus.