Sexual Dimorphism Of Cerebral Cortex In Chinese Cohorts

Human brain is the most important and complicated organ in human body with the most complicated. It can control and regulate spiritual and body movement and also maintain the stable condition (e.g., breath, heartbeat, endocrine, etc.) in human body. The sexual differences in cerebral structures can induce the differences of behavior in males and females. Males are good at spatial and abstract abilities, while females are good at language and memory abilities. The sexual differences of human brain have been studied by many researchers from they were found.Some researchers have found that cerebral volumes in males are bigger than those in females using anatomic methods. Then, a lot of gender differences were found in gray matter, white matter, surface area, cortical thickness and regional structures (hippocampus), etc. However, there are also some conflicts about the results due to using different methods. In addition, anatomic studies have several disadvantages such as lack of specimen, time consuming, relative bigger error of measurement, which restrict the development of anatomic studies. With the rapid advance of imaging and computer methods, the classical anatomic methods are being replaced by imaging anatomic methods. Using imaging anatomic methods, we can collect big samples of imaging data easily. Then, we can also analyze the data using advanced computer methods with relative smaller errors and better reproducibility. As most research data were from foreigners, Chinese materials are lacking but important. Chinese people, which take up nearly one fifth of the population all over the world, are the typical Oriental representation. Thus, it is needed to collect and analyze the data of Chinese people, which can provide morphological basis for the functional studies of human brain and diagnosis of diseases in central nerve system.In this study, with advanced computer methods, we analyzed the sexual and asymmetry differences of Chinese human cerebrum using high resolution MR imaging data of Chinese young adults.This study is consisted of 3 parts, abstracts of which are as followed: Part 1:Sexual Dimorphism of Chinese Cerebral VolumeSection 1:Sexual dimorphism of entire volume in Chinese cerebrumsPurpose:To investigate the sexual dimorphism and asymmetry differences of global volume in Chinese cerebrums using a voxel-based method.Materials and methods:sixty-nine healthy, right-handed and gender-matched Chinese young adults (male 30, female 39; aged 23.9±3.4 yr). To minimize the influences of age and possible interactions of age with gender, the subjects were recruited from a relatively narrow age range (18-27 years). The MR examinations were performed with a GE (General Electric, Milwaukee, USA) 3.0-T MRI Scanner. Subsequently, thin sectional MR data were obtained using transverse 3D T1-weighted fast spoiled gradient-echo (FSPGR) sequence. Firstly, nonbrain tissues were deleted from the MRI scans using the BET. Then manual corrections, as needed, were applied. Subsequently, automated tissue segmentation was conducted for each volume data set to classify voxels into gray matter (GM), white matter (WM), cerebrospinal fluid (CSF) on the basis of signal intensity. Then, using Partial Volume Classifier tool, each voxel is classified according to the tissue type. The volumes of cerebral structures in the native space were measured using Compute Volume tool in FreeSurfer software. The cerebral surface was reconstructed automatically and the surface area and gyrification was computed using ShapeReport tool. All individual cerebrums were linearly aligned to an average brain template using 12 parameters transformation and resample, then a minimal deformation target (MDT₆9) was established, according to which Jacobian value for each individual subject was obtained. The cerebral volume and gyrification in the MDT₆9 space was obtained using the individual Jacobian value. Finally, sexual and asymmetry differences of volume values in gray and white matters, surface area and gyrification were analyzed using statistical methods.Results:1. Sexual differences:Before the spatial normalization, all the volumetric parameters are larger in males than those in females bilaterally. After the normalization, the parameters which are significant larger (P< 0.05) in males than that in females include right gray volume, left surface gyrification, while the parameters significant larger (P< 0.05) in females include left and right entire volume, right whiter matter volume, left and right surface area.2. Asymmetry differences:Before the spatial normalization, in males and females, all the volumetric parameters are larger in left than those in right, except for volume of white matter in females which is larger in right. After the normalization, the parameters which are significant larger (P< 0.05) in left than right hemisphere include male hemispheric volume, male gray volume, female hemispheric volume female gray volume, while the parameters significant larger (P< 0.05) in right side include female whiter matter volume. No asymmetry differences of male and female surface area and gyrification were found (P> 0.05).Conclusions:There are some significant sexual differences in the entire hemispheric, gray and white matters, while asymmetry differences were only found in volume parameters, which provide the morphologic basis for sexual dimorphism studies on cerebral function.Section 2:Sexual dimorphism of regional volume in Chinese cerebrumsPurpose:To investigate the sexual dimorphism and asymmetry differences of regional volume in Chinese cerebrums using a voxel-based method.Materials and methods:high-resolution MR imaging data were obtained from sixty-nine healthy, right-handed and gender-matched Chinese young adults with a GE 3.0-T MRI Scanner. The transverse 3D FSPGR sequence was employed. Firstly,54 structures were segmented automatically using LONI BrainParse software. Then using Compute Volume tool in Freesurfer software, the volume of 54 structures and 6 regions (frontal, parietal, temporal, occipital lobes, insular and cingulate gyrus) in native space was calculated according to the voxel number. Subsequently, these volume values in the MDT₆9 space were obtained using the Jacobian value of each individual subject. Finally, sexual and asymmetry differences of volume in regional gray matter were analyzed using statistical methods.Results:1 Results of cerebral regions1.1 Sexual differences: The regions which were significant larger (P< 0.05) in males than that in females include left and right insulars, while the regions significant larger (P< 0.05) in females include left and right frontal lobes, left and right parietal lobes.1.2 Asymmetry differences:The regions which are significant larger (P< 0.05) in left than right hemisphere in males include temporal lobe and insular, while the regions significant larger (P< 0.05) in right side in males include parietal and occipital lobes.In females, the regions which are significant larger (P< 0.05) in left than right hemisphere include temporal lobe and insular, while the regions significant larger (P< 0.05) in right side include cingulate gyrus, frontal, parietal and occipital lobes.2 Results of regional structures2.1 Sexual differences:In left hemisphere, the structures which were significant larger (P< 0.05) in males than that in females include lateral orbitofrontal gyrus, while the structures significant larger (P< 0.05) in females include superior and middle frontal gyri, middle orbitofrontal gyrus, superior and middle occipital gyri, parahippocampal gurus, haipocampus, caudate nucleus, putamen.In right hemisphere, he structures which were significant larger (P< 0.05) in males than that in females include inferior frontal gyrus, while the structures significant larger (P< 0.05) in females include superior and middle frontal gyri, middle orbitofrontal gyrus, precentral gyrus, superior parietal and occipital gyri, cuneus, precuneus, parahippocampal gurus, caudate nucleus. 2.2 Asymmetry differences:In males, the structures which are significant larger (P< 0.05) in left than right hemisphere include superior frontal gyrus, rectal gyrus, precuneus, parahippocampal gyrus, fusiform gyrus, while the structures significant larger (P< 0.05) in right side include middle frontal gyrus, precentral gyrus, middle orbitofrontal gyrus, superior parietal gyrus, angular gyrus, middle and inferior occipital gyri, cuneus, caudate nucleus.In females, the structures which are significant larger (P< 0.05) in left than right hemisphere include superior frontal gyrus, rectal gyrus, precuneus, superior and inferior temporal gyrus, parahippocampal gyrus, hippocampus, fusiform gyrus, putamen, while the structures significant larger (P< 0.05) in right side include cingulate middle frontal gyrus, precentral gyrus, middle and lateral orbitofrontal gyri, superior parietal gyrus, angular gyrus, middle and inferior gyri, cuneus, middle temporal gyrus, lingual gyrus, caudate nucleus.Conclusions:Most regional gray volume in both hemispheres is larger in females than males. In addition, most regional gray volume in males and females is larger in right side. These differences may be correlated with the sexual dimorphism of function in corresponding structures.Part 2:Sexual Dimorphism of Cortical Thickness in Chinese CerebrumsPurpose:Purpose:To investigate the sexual dimorphism and asymmetry differences of cortical thickness in Chinese cerebrums using high-resolution MRI data.Materials and methods:High-resolution MR imaging data were obtained from sixty-nine healthy, right-handed and gender-matched Chinese young adults (male 30, female 39; aged 23.9±3.4 yr) using a GE 3.0-T MRI Scanner. The transverse 3D FSPGR sequence was employed. Automated tissue segmentation was conducted for each volume data set to classify voxels into GM, WM and CSF on the basis of signal intensity. Cortical thickness of each point in cerebral surface, which was defined as the shortest Euclidean distance between GM/WM boundary and GM/CSF boundary, was measured and mapped. This thickness map was spatial normalized into using MDT₆9 space. Finally, sexual and asymmetry differences of cortical thickness were analyzed using statistical methods.Results:1. Sexual differences:In left hemisphere, the regions with larger cortical thickness (P< 0.01) in males than females include posterior parts of superior and middle frontal gyri, inferior frontal gyrus, inferior parts of precentral and postcentral gyri, anterior parts of cingulate gyrus, posterior parts of rectal and obital gyri, anterior parts of superior and middle temporal gyri, inferior temporal gyrus, parahippocampal gyrus, paracentral gyrus, precuneus, cuneus, while the regions with larger cortical thickness (P< 0.01) in females include anterior parts of superior, middle and inferior parts of frontal gyri, superior parts of postcentral and inferior parietal gyri, superior parietal gyrus, anterior partes of rectal and obital gyri.In right hemisphere, the regions with larger cortical thickness (P< 0.01) in males than females include anterior parts of superior, middle and inferior frontal gyri, inferior parts of precentral and postcentral gyri, superior part of middle temporal gyrus, superior temporal gyrus, parahappicampal gyrus, anterior part of paracentral gyrus, posterior part of precuneus, cuneus, posterior parts of orbital and rectal gyri, while the regions with larger cortical thickness (P< 0.01) in females include anterior parts of superior, middle and inferior frontal gyri, superior parts of precentral and postcentral gyri, superior parietal gyrus, inferior part of inferior parietal gyrus, anterior partes of rectal and obital gyri. 2. Asymmetry differences:In males, the regions with larger cortical thickness (P< 0.01) in left hemisphere include anterior parts of middle and inferior frontal gyri, superior part of middle temporal gyrus, middle part of inferior temporal gyrus, anterior part of paracentral gyrus, while the regions with larger cortical thickness (P< 0.01) in right side include superior part of superior temporal gyrus, inferior part of parahippocampal gyrus, anterior part of cuneus.In females, the regions which with larger cortical thickness (P< 0.01) in left hemisphere include mid-superior and post-inferior parts of superior temporal gyri, while the regions with larger cortical thickness (P< 0.01) in right side include posterior parts of superior, middle and inferior temporal gyri, middle part of precentral gyrus, posterior parts of parahippocampal and superior parietal gyri.Conclusion:There were some significant sexual differences of cortical thickness involving frontal, parietal, temporal and occipital lobes, while less regions with significant asymmetry differences of cortical thickness were found.Part 3:Sexual Dimorphism of Chinese Central SulcusPurpose:To investigate the sexual dimorphism and asymmetry differences of sulcal parameters in Chinese central sulcus using a 3D ribbon method.Materials and methods:High-resolution 3D FSPGR MR imaging data were obtained from 60 healthy, right-handed and gender-matched Chinese young adults (male 30, female 30; aged 23.3±2.9) using a GE 3.0-T MRI Scanner. The central sulci were reconstructed according sulcal signal intensity using a 3D ribbon method by BrainVisa software. Then, sucal lengthy depth and width was measured automatically based on the reconstructed sulcal model. We divided the CS into 4 sulcal shapes according to whether the CS connects with the medial surface and/or the Sylvian fissure. Finally, sexual and asymmetry differences of sulcal parameters were analyzed using statistical methods.Results:1 Sulcal parameters1.1 Sexual differences:Before the normalization, sulcal length, depth and width were all significantly larger (P< 0.05) in males compared to females in the left central sulci and right central sulci. After the normalization, no significant sexual differences (P> 0.05) of sulcal length, depth and width were found in both hemispheres.1.2 Asymmetry differences:Before the normalization, significant leftward asymmetry of sulcal length, depth and width (P< 0.05) was found in males and females. After the normalization, significant leftward asymmetry (P< 0.05) of sulcal depth and width were found in males. In females, only sulcal depth revealed significant leftward asymmetry (P< 0.05).1.3 Sulcal patterns:Type a (CS does not connect with medial surface or Sylvian fissure) was dominant in females (Left:63.33%, Right:46.67%). Whereas Type b (CS connects with medial surface but not with Sylvian fissure) was dominant in males (Left:63.33%, Right:60.00%). No significant sulcal shape asymmetry (P>0.05) were found in males, females or the entire group. Significant gender dimorphism (P< 0.05) of the sulcal patterns were only found in the left central sulci.Conclusion:There were some significant sexual and asymmetry differences in sulcal parameters of Chinese central sulcus, which could be reduced by the spatial normalization.Conclusions and Significances Sexual dimorphism and asymmetry differences of cerebral volume, cortical thickness and sulcal morphology in Chinese human cerebrum were firstly studied systematically using a relative big sample of high-resoltion 3D MRI data. A series of advanced computer methods were employed in this study, which can provide the morphological basis for the functional studies and diagnosis of diseases in central nerve system.