Gender Difference And Asymmetry Of Hippocampal Subfields Volume In Adolescents

Background:The hippocampus is one of the important brain regions of the medial temporal lobe,which plays an important role in memory,aging,mental diseases and neurodegenerative diseases.Studies at the histological level divide the hippocampus into different subfields according to the types,morphological structures and functional connections of the cells inside the hippocampus.The segmentation protocols of the subregion vary greatly in different studies,but the relatively recognized subfields include CAl-4,dentate gyrus,subiculum and so on.Different hippocampal subfields play different roles in the memory system,and different mental diseases or neurodegenerative diseases selectively affect different subfields in the development.Therefore,it is of great significance to explore the structure and function of the hippocampal subfields for the study of brain cognitive function and related diseases.With the development of magnetic resonance technology and computer algorithms,it is possible to segment the hippocampal subfields based on MRI in vivo.More and more segmentation methods and software have been developed,and they have made great achievements in the study of mental diseases and Alzheimer’s disease.However,in previous studies,the research of hippocampal subfields under healthy subjects is still insufficient,and the conclusions of gender difference and bilateral difference in hippocampal subfields volume are controversial,which may be due to the influence of many factors such as segmentation protocol and image acquisition.Therefore,it is of great significance to analyze the gender and bilateral differences in normal hippocampal subfields.In the adolescent period,people have strong learning and memory ability and active hippocampal function.Analysis of the structure of human hippocampal subfields in this period can help reveal the performance of the hippocampus at its peak state in the life process.Moreover,as the hippocampus is closely related to neurodegenerative diseases,researches on the hippocampus are more focused on the advanced age group.A more comprehensive analysis of the hippocampus subfields in adolescent stage can be a better supplement for clinical disease research.Based on the above problems,3.0T MR images of adolescents were collected in this study.The Freesurfer software was used to automatically segment 19 labels of the hippocampal subregion,obtain both HBT and FS60 images,and the volume data of the hippocampal subregion was obtained.Statistical analysis was conducted to analyze the gender and bilateral differences in the hippocampal subfields of adolescents.Objective:To segment and reconstruct the hippocampal subfields of adolescents,to obtain the volume data,and to analyze the gender and bilateral differences by statistical analysis.To reveal the developmental state of the hippocampus during adolescence,to supplement the structural data of the developmental stage of the hippocampus,and to provide more anatomical basis for clinical disease research.Methods:101 healthy right-handed adolescents aged 15-20 years were recruited and screened(57 males,mean age 17,11±1.31 years;44 females(mean age 17.45±1.36 years).T1 images of brain were obtained using a 3.0T GE Signa MR scanner.The image and data processing steps are as follows:1.Format conversion by MRIcron software;2.The image in NIFTI format was imported into Freesurferv7.1.0 software,and the intracranial volume data was extracted after processing with Recon-all command,3.Segmentha_t1.sh command was used to automatically segment the hippocampal subfields,and the volume data was obtained after segmentation,4.Intracranial volume was used to standardize the volume of hippocampal subregion in two ways:Cendes method and the covariance method,5.Gender and bilateral differences in hippocampal subfields volume were analyzed in two different standardized methods.Results:1.Freesurfer software showed clear and good effect in automatic segmentation of hippocampal subfields.2.In terms of bilateral differences,the two standardized methods obtained the same results:in HBT,except for the hippocampus tail,there were bilateral differences in the volume of the hippocampus head,body and the whole hippocampus,R>L.In FS60,there was no bilateral difference in hippocampal tail,hippocampal fissure and subiculum;other subfields have bilateral difference,the volume of CA1,CA3,CA4,GC-ML-DG,molecular layer,HATA,fimbria is R>L,while parasubiculum and presubiculum is L>R.3.In terms of gender difference,the results obtained by the two different standardized methods are far different.When data standardized by the Cendes method,there is gender difference in the volume of each part on the both sides of the HBT,and F>M.FS60;in left hippocampus,there is gender difference in parasubiculum,presubiculum,subiculum,CA4,GC-ML-DG,molecular layer,HATA,and hippocampal tail,F>M.In right hippocampus,there is gender difference in parasubiculum,presubiculum,subiculum,CA1,CA4,GC-ML-DG,molecular layer,HATA,hippocampal tail and hippocampal fissure,F>M.But when the covariance method was used for standardization,there were no gender difference in all subfieldsConclusion:FreeSurfer software can be used to segment the hippocampal subfields well,and obtain the volume data for statistical analysis.The hippocampus head show significant bilateral difference.Except for the hippocampus tail,there were bilateral differences in the hippocampus CA area,dentate gyrus and other important functional areas,which may be related to the lateralization of left and right brain functions.When two different standardized methods were used to compare gender differences,the results are different.The Cendes method showed a stronger gender difference,F>M,while the covariance method showed no gender difference,which may be because the covariance method eliminated the influence of ICV to a greater extent.The results of this study have both similarities and differences with previous studies,which is a supplement to the study of the hippocampus subfields.It better presents the volume data of the hippocampus subfields during adolescence,and can provide an anatomical basis for the study of clinical psychiatric diseases and neurodegenerative diseases.