Brain Morphometry Differences Between Chinese And Caucasian Cohorts And The Impact Of Love On Brain Functional Connectivity

Differences in genetics,culture,and environmental exposures may lead to brain structure and functional differences between various populations.There is extensive evidence suggesting that culture and sustained experiences could affect brain and behavior.Recent neuroimaging studies have revealed cultural differences in neural correlation of cognition and behavior.These studies,comparing functional magnetic resonance imaging(fMRI)results of East Asians and Westerners,found stable differences in attention,categorization,and contextual processing between the two groups.Cultural differences have been shown to influence linguistic functions and nonlinguistic neural function of the brain.Although a great number of behavioral observations and fMRI studies suggested neural differences between cultures,possible corresponding differences in brain structure have not been adequately investigated.To date,only a few structural imaging studies have explored the brain structural differences between East Asians and Westerners.Brain asymmetry has been observed in terms of structure,function,behavior and their correlations.This lateralized specification of the human brain varies with handedness,gender and age,and is thought to originate from evolutionary,developmental,hereditary,experiential and pathological factors.Although asymmetry of function is thought to be a hallmark feature of brain organization in the human cortex,the mechanisms underlying brain structural and functional asymmetries are far from fully understood.Recently,with the development of magnetic resonance imaging(MRI)image processing techniques for brain registration and automatic structural segmentation,extensive brain asymmetry studies have been done to explore regional or localized inter-hemispheric differences in brain structural measures,which could reveal anatomical correlates of functional lateralization.However,most of these studies were focused on a single brain morphological measure,e.g.the cortical thickness,cortical volume,cortical surface area or local gyrification,which may convey brain structural properties that are unique to others.Thus,a complete understanding the brain structural asymmetry requires a systematical analysis of all these metrics,as well as how these indices of asymmetry relate to each other.Most of existing brain asymmetry findings were originated from the Westerners,and the brain structural and functional asymmetries of East Asians still remains unclear.Differences in genetics,culture and environmental exposures may lead to asymmetrical differences in brain structure and function between the two races.Thus,brain asymmetry findings obtained from Westerners are likely not applicable to East Asians.Few efforts have been made to investigate the difference between East Asians and Westerners in brain structural asymmetries.Studying East Asians’ brain structural asymmetries and the related ethnic differences from Westerners could be proved important at methodological and neurocognitive levels.Structural MRI is an integral part of assessing functional and behavioral differences.Morphometry is a valuable tool for studying human brain plasticity in vivo,and anatomical brain differences play a primary and critical role in the origination of functional and behavioral differences.Although the above structural imaging studies have examined differences in brain structure between East Asians and Westerners,the locations and extent of the differences between these two cohorts are still poorly understood.In the present study,we explored the cultural/ethnicity-based brain differences with high quality structural MRI data from comparatively large samples of education-matched right-handed young Chinese and Caucasian cohorts.Comprehensive surface-based morphometry analyses were conducted across the brain for multiple structural measurements:cortical thickness,cortical volumes,and surface area and asymmetry index,so as to assess the cultural/ethnicity-based differences in structural brain asymmetries between Chinese and Caucasian.In addition,romantic love is considered to be a human common experience and has an obvious effect on our lives,which can lead to the brain structure and function differences in diverse races.the present study,we computed ReHo,DC,ALFF,fALFF and functional connectivity analysis from resting-state fMRI data to investigate alterations in functional brain architecture in undergraduate romantic lovers.This study is divided into three parts.Part 1:Brain structure differences between Chinese and Caucasian cohortsObjective:Although a great number of behavioral observations and fMRI studies suggested neural differences between cultures,possible corresponding differences in brain structure have not been adequately investigated.To date,only a few structural imaging studies have explored the brain structural differences between East Asians and Westerners,the locations and extent of the differences between these two cohorts are still poorly understood.In the present study,we explored the cultural/ethnicity-based brain differences with high quality structural MRI data from comparatively large samples of education-matched right-handed young Chinese and Caucasian cohorts.Comprehensive surface-based morphometry analyses were conducted across the brain for multiple structural measurements:cortical thickness,cortical volumes,and surface area,so as to investigate differences between Chinese and Caucasian.Materials and methods:45 right-handed Chinese male volunteers(aged from 20 to 30 years),were recruited from the local community through the research center for sectional and imaging anatomy at Shandong University Cheeloo College of Medicine.45 right-handed,healthy Caucasian male subjects(aged from 22 to 29 years)were selected from the Human Connectome Project(HCP)datasets.T1-weighted structural MRI data of the 45 Chinese volunteers and 45 Caucasian participants were acquired on a Siemens 3.0 T Skyra MRI scanner(Siemens AG,Erlangen,Germany)using a 32-channel head coil.All the structural MR images were processed using the FreeSurfer software(version5.3.0)to reconstruct the cortical surfaces and measure the brain structural features of cortical thickness,cortical volume and surface area.Then vertex-wise surface-based morphometric analyses were implemented using the SurfStat toolbox.Besides,we performed a VBM analysis using the VBM8 toolbox to confirm the cortical differences between the Chinese and Caucasian cohorts.Results:We performed comprehensive SBM and VBM analyses of multiple brain structural features of each cohort,and identified significant between-group differences in cortical thickness,cortical volume,and cortical surface area,as well as gray matter intensity consistently in distributed brain regions,including the frontal,temporal,parietal,occipital,insular,and cingulate cortices(see Figures 1-4 and Supporting Information).The Chinese population showed greater structural features in the temporal lobe and cingulate gyrus,and smaller features in the frontal lobe and parietal lobe,compared with the Caucasian cohort.Conclusion:Here we performed a comprehensive vertex-wise morphometric analysis of the brain structures between Chinese and Caucasian cohorts and identified consistent significant between-group differences in cortical thickness,volume and surface area in the frontal,temporal,parietal,occipital,and insular lobes as well as the cingulate cortices.These findings systematically revealed comprehensive brain structural differences between young male Chinese and Caucasians,and provided new neuroanatomical insights to the behavioral and functional distinctions in the two cultural/ethnic populations.Part 2:Brain asymmetry differences between Chinese and Caucasian populationsObjective:Brain asymmetry has been observed in terms of structure,function,behavior and their correlations.This lateralized specification of the human brain varies with handedness,gender and age,and is thought to originate from evolutionary,developmental,hereditary,experiential and pathological factors.Recently,with the development of magnetic resonance imaging(MRI)image processing techniques for brain registration and automatic structural segmentation,extensive brain asymmetry studies have been done to explore regional or localized inter-hemispheric differences in brain structural measures,which could reveal anatomical correlates of functional lateralization.However,most of these studies were focused on a single brain morphological measure,most of existing brain asymmetry findings were originated from the Westerners,and the brain structural and functional asymmetries of East Asians still remains unclear.Differences in genetics,culture and environmental exposures may lead to asymmetrical differences in brain structure and function between the two races.Studying East Asians’ brain structural asymmetries and the related ethnic differences from Westerners could be proved important at methodological and neurocognitive levels.In this study,we explored the localized asymmetries of brain structure using the features of cortical thickness,surface area and volume across the brain in two groups of right-handed,Chinese and Caucasian male young adults,which were well-matched in age and education,so as to assess the cultural/ethnicity-based differences in structural brain asymmetries between Chinese and Caucasian.Materials and methods:45 right-handed Chinese male volunteers(aged from 20 to 30 years),were recruited from the local community through the research center for sectional and imaging anatomy at Shandong University Cheeloo College of Medicine.45 right-handed,healthy Caucasian male subjects(aged from 22 to 29 years)were selected from the Human Connectome Project(HCP)datasets.T1-weighted structural MRI data of the 45 Chinese volunteers and 45 Caucasian participants were acquired on a Siemens 3.0 T Skyra MRI scanner(Siemens AG,Erlangen,Germany)using a 32-channel head coil.All the structural MR images were processed using the FreeSurfer software(version5.3.0)to reconstruct the cortical surfaces and measure the brain structural features of cortical thickness,cortical volume and surface area.Then vertex-wise surface-based morphometric analyses were implemented using the SurfStat toolbox,which is a Matlab toolbox for the statistical analysis of surface data using linear mixed effects models.Asymmetries Index(AI)for each cortical feature i.e.,cortical volume,surface area and cortical thickness were calculated.Results:The Chinese group showed consistent inter-hemispheric asymmetries in the three brain morphological measures in multiple brain regions,including the temporal,frontal,parietal,occipital,insular cortices and the cingulate gyrus.Moreover,we also found that Chinese and Caucasian populations showed different brain asymmetries(see Fig.1-6).Compared with the Caucasian group,the Chinese group showed greater structure asymmetries in the frontal,temporal,occipital and insular cortices,and smaller asymmetries in the parietal lobe and cingulate gyrus.Conclusion:This study systematically revealed the brain asymmetry patterns in cortical surface area,thickness and volume in right-handed Chinese and Caucasian male young adults,and further revealed the between-group differences in brain structural asymmetry in the frontal,temporal,occipital parietal and insular cortices as well as cingulate gyrus.The current study may contribute to an improved understanding of the human brain structural and functional asymmetry between Chinese and Caucasian,and would provide a foundation for studying abnormal brain asymmetry in cognitive and neuropsychiatric disorders.In addition,the significant brain asymmetry differences between different ethnicities might motivate the creation and use of ethnicity-specific brain templates and atlas.Part 3:The impact of love on brain functional connectivity in young adultsObjective:Experiences affect structure and function of human brain.Romantic love is becoming more and more common experiences in college students,which can affect their behavior and psychology to some extent.Neuroimaging studies of romantic love have investigated early-stage,intense romantic love as well as long-term romantic love,the participants include the Chinese,Americans and British.Meanwhile,many psychologists have studied sex differences in love relationships and there are definitely indications that neurobiological systems in love are partly gender specific.Previous studies have shown that male and female lovers differ in various ways.However,not enough attention has been paid to the effects of falling in love on the brain for college students.Given that romantic love represents a dynamic process in the brain and that there are gender differences in love relationships,we chose the length of the relationship and gender as two criterions in undergraduate participants.In the present study,we computed ReHo,DC,ALFF,fALFF and functional connectivity analysis from resting-state fMRI data to investigate alterations in functional brain architecture in undergraduate romantic lovers.Materials and methods:119 healthy college students were enrolled in the study.They were interviewed at the beginning of the study procedure regarding previous romantic relationships and demographic characteristics.The participants were divided into four groups according to their previous romantic relationship:(1)the "female love",group(FLG,N=30,aged 21.80±1.54 years),consisting of females with a reported duration of "being in a romantic relationship" for at least one year;(2)the "male love" group(MLG,N=30,aged 21.30±1.82 years),consisting of males currently intensely in love for at least one year;(3)the "female single" group(FSG,N=30,aged 21.81±1.60 years),consisting of females who had never fallen in love with anyone;(4)the“male single" group(MSG,N=29,aged 21.09±1.70 years),consisting of males who had never fallen in love with anyone.All imaging data were acquired on a Siemens 3.0T Skyra MRI scanner(Siemens AG,Erlangen,Germany)using a 32-channel head coil.T1-weighted structural MRI sequence relevant to this study was a three-dimensional(3D)MP-RAGE optimized for gray-white matter contrast.The resting-state fMRI data were preprocessed by SPM8,DPARSF.Results:In the present study,we used functional connectivity analysis to investigate the changed brain areas and corresponding functional alterations of being in love group(people who fell in love and were in a romantic relationship)compared with those single group(people who have never been in love and not in a romantic relationship)in young adults.The hub analysis revealed significant decreased DC,ALFF,fALFF and ReHo in left lingual gyrus in female love group and increased fALFF,ALFF and ReHo in left precuneus in female love group.Subsequent functional connectivity analyses of left lingual gyrus revealed decreased functional connectivity with the superior temporal gyrus,parietal lobe,insula,cingulate gyrus and cuneus.Conclusion:In summary,we investigated the changed brain areas and corresponding functional alterations between being in love group and single group in college students.According to the female romantic group,love-related brain functional alterations included decreased DC of the left lingual gyrus and increased fALFF of the left precuneus.Whole brain functional connectivity analysis revealed decreased functional connections in the superior temporal gyrus,parietal lobe,insula,cingulate gyrus,cuneus,and increased functional connections between the left inferior and middle of occipital gyrus.