Comprehensive cortical thickness and surface area comparison between young Uyghur and Han Chinese cohorts

    Comprehensive Cortical Thickness and Surface Area Comparison between Young Uyghur and Han Chinese Cohorts Jun Lu, Chunhui Jiang, Jian Wang, Wenxiao Jia PII: DOI: Reference:

S0730-725X(16)30011-X doi: 10.1016/j.mri.2016.03.018 MRI 8531

To appear in:

Magnetic Resonance Imaging

Received date: Revised date: Accepted date:

4 November 2015 4 March 2016 27 March 2016

Please cite this article as: Lu Jun, Jiang Chunhui, Wang Jian, Jia Wenxiao, Comprehensive Cortical Thickness and Surface Area Comparison between Young Uyghur and Han Chinese Cohorts, Magnetic Resonance Imaging (2016), doi: 10.1016/j.mri.2016.03.018

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Comprehensive Cortical Thickness and Surface Area Comparison between Young

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Uyghur and Han Chinese Cohorts

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Jun Lu1, Chunhui Jiang1, Jian Wang1*, Wenxiao Jia2 **

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1 Imaging Center, First Affiliated Hospital, Xinjiang Medical University, Urumqi, 830011,

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China

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2 Xinjiang Medical University, Urumqi, 830011, China

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E-mail: *Corresponding [email protected]

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E-mail: **Corresponding [email protected]

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Comprehensive Cortical Thickness and Surface Area Comparison between Young

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Uyghur and Han Chinese Cohorts

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Abstract

We hypothesized that the brain structural differences as discovered previously between

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Westerners and East Asians could also be revealed between Han Chinese and Uyghur, which were genetically related ethnic groups with distinct languages. We conducted a brain

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MRI structural comparison in terms of cortical thickness and surface area between 15 healthy young Uyghurs and 15 age-matched Han Chinese. Widespread regions with significantly greater cortical thickness were found in the Uyghurs, and their distribution showed strong resemblance to previous “Westerners vs. Asians” findings. While surface area analysis displayed less widespread brain differences. Notably, our detected regions with

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structural differences contained a large part of language-specific or at least closely language-related brain areas, which may partly be attributable to the brain plasticity

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respectively driven by Uyghur and Mandarin. Our findings will help to better understand the

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neurobiological basis of interethnic differences along with the language processing mechanisms of Han Chinese and Uyghur.

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Key words: Cortical Thickness, Surface Area, Han Chinese, Mandarin, Uyghur

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1. Introduction Increasing structural imaging evidences have indicated that the brain structure is diverse

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across genetics (Geschwind et al., 2002; Thompson et al., 2001), gender (Luders et al., 2006;

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Sowell et al., 2007), age (Hogstrom et al., 2012), diseases (Julkunen et al., 2010; Schultz et al., 2010) etc. Comparison between different ethnic groups may provide hints to trace the

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internal and external factors responsible for brain’s formation and alteration in structure. To date, a series of cross-ethnic studies have confirmed that the brain structure is diverse among

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different ethnic groups, say, Westerners and East Asians (Chee et al., 2011; Crinion et al., 2009; Green et al., 2007; Kochunov et al., 2003; Zilles et al., 2001). These observed differences are probably attributable to genetic and environmental factors, and the latter include language driven effect (Kochunov et al., 2003), culture-related behavior (Nisbett

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and Miyamoto 2005), or bias in diet (Kalmijn et al., 2004) etc. While debates still exist over which one plays a dominating role in the interethnic brain structure differences. Moreover,

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majority of the available cross-ethnic studies on brain structure differences, though positive findings were gained, mainly focused on the differences between two ethnic groups with

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different cultures, geographic locations and genetics (e.g. Caucasians vs. Asians). Therefore, studies concerning two genetically related ethnic groups will help to understand to what

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extent and by what mean the ethnic factors affect brain structure. Uyghur provides an appropriate model of “genetic transition” between East Asians and Europeans. Uyghur is one of the largest minorities in Xinjiang Uyghur Autonomous Region of China (located in the middle part of the Eurasian Continent) accounting for 46% (9.87 million) of the total population in Xinjiang. In terms of genetics, Uyghur is a substantial admixture of East Asian and European ancestry in the ratio of (East Asian: European) 40:60 (Xu et al., 2008), 53:47 and 48:52 (Xu and Jin 2008), 69:31 (Li et al., 2009), or 57:43 (Yao et al., 2004). Besides that, the Uyghurs conserve their unique language – Uyghur, which is significantly different from the Han Chinese character in terms of both structure and pronunciation (Engesth et al., 2009). By the contrast between Han Chinese and Uyghurs, the admixture with roughly half East Asian ancestry and half European ancestry, the results

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obtained from this study would provide valuable evidence for studying the effect of ethnicity upon brain structure. Cortical thickness which is one interesting aspect of brain structure has been

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emphasized recently by researchers on its susceptibility by postnatal factors, thus underlying

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its compatibility in studying the external (or environmental) factors of ethnicity on brain’s formation and alteration; on the other hand, cortical surface area as another structural aspect

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is believed to reflect more genetic-related information and has advantage over thickness in detecting the internal (or inherited) cross-ethnic differences in brain structure (Eyler et al.,

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2011; Hosseini et al., 2013; McGinnis et al., 2011; Rimol et al., 2010). So, in this study we selected these two metrics to comprehensively explore the brain structural differences between Uyghurs and Han Chinese.

To data, five cross-ethnic studies between Westerners and East Asians were conducted

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to evaluate brain’s interethnic structural differences along with its anatomical plasticity driven by languages using MRI (Chee et al., 2011; Crinion et al., 2009; Green et al., 2007;

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Kochunov et al., 2003; Zilles et al., 2001). However, no findings were documented concerning two distinct but affirmatively genetic-related ethnic groups. To further

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understand the role of ethnic factor plays on the diversity of brain structure, we would like to compare populations who are genetic-related to find out (i) whether the ethnicity still be a

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reason which can lead to detectable brain structure variation (especially large scale differences) by imaging morphometry, (ii) whether regional differences can be found in some brain areas with specific functions, which are able to be related to the different social cognitions, behaviors, or experiences between the two ethnic groups (e.g. languages’ driven effect upon brain structure addressed in previous cross-ethnic studies (Crinion et al., 2009; Kochunov et al., 2003)). This study would not only help to shed light on the neurobiological basis for interethnic cognition and behavior differences (e.g. racial attitudes, prejudice, or type of behaviors (Kubota et al., 2012)) between Uyghur and Han Chinese for further studies, but also provide evidences for the construction of ethnic-specific brain templates for further neuroimaging studies on Uyghur.

2. Methods

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2.1 Participants Fifteen young Uyghurs (8 female and 7 male, 18.3±0.5 years old) and 15 young Han

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Chinese (8 female and 7 female, 18.4±0.7 years old) were recruited. The Uyghurs were all

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undergraduate volunteers enrolled in formal Uyghur education system which the medium of instruction was Uyghur and they rarely contacted people who speak Mandarin. The Han Chinese were also all undergraduate volunteers enrolled in formal Chinese education system

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which the medium of instruction was Mandarin. Exclusion criteria of both groups include

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history of brain trauma, neural related diseases and bilingual speakers in Uyghur and Mandarin. Each individual received detailed language tests before the experiment, including spontaneous oral expression, reading and comprehension, listening, naming and repetition to verify their language proficiency. All subjects were right-handed and were informed with a written consent form. Ethical approval for the study was obtained from the university and

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hospital ethics committee. Two groups were well matched in gender, age, education, and handedness, and language proficiency. Demographic details and language tests results were

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summarized in Table 1.

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2.2 Data Acquisition

High resolution T1-weighted data of the whole brain was obtained from a 3.0T MRI scanner

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(Signa HDx, GE Healthcare, Milwaukee, WI) with 8-channel head coil and FSPGR sequence (TR =7.8ms, TE=1.7ms, flip angle=20°, slice thickness=1.0mm，number of excitation =1, FOV=240mm×240mm, and matrix=240×240mm). 2.3 Imaging Data Analysis The data analysis of the cortical thickness was performed using a well-recognized software, the Freesurfer (http://surfer.nmr.mgh.harvard.edu), developed by Fischl and Dale (Dale et al., 1999; Fischl and Dale 2000; Fischl et al., 1999). Freesurfer consists of automated tools for reconstruction of the brain from structural MRI data, facilitating the quantification of cortical metrics using a spatially unbiased analysis.First, a surface representation of each participant’s anatomy was created by inflating each hemisphere of the anatomical volumes to a surface representation. The resulting surface representation was aligned to a template of

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average curvature.These surface representations were obtained by submitting each participant’s MRI to a series of steps that included: (1) motion correction and affine transformation to Talairach space, (2) intensity normalization, (3) removal of non-brain

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voxels, (4) segmentation of grey matter (GM), white matter (WM) and cerebrospinal fluid(CSF), and, finally (5) tessellation of the GM/WM boundary, and automated topology correction. At each step, the results were visually inspected and manual interventions were

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performed when required to correct topological defects. The cortical thickness was defined as the vertex distance between the inner cortical surface which was the boundary between

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WM and GM, and the outer cortical surface which was the boundary between the GM and CSF or referred as pial surface.The WM was segmented by classifying all white matter voxels according to the method descripted by Dale et al (Dale et al., 1999). The connected WM voxels were then refined to represent the GM/WM boundary as an initial contour

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followed by deforming outward to obtain the pial surface (Dale et al., 1999; Fischl and Dale 2000). Then the cortical thickness of each vertex on one surface was measured by the

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average distance between the target vertex to the closest corresponding point on the other surface (Dale et al., 1999; Fischl and Dale 2000). While the surface area was defined as the

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shortest distance between equivalent vertices in the pail and gray-white matter surfaces (Dale et al., 1999). To achieve the inter-subject spatial normalization, the inflated inner

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cortical surface was registered to an averaged spherical surface followed by mapping, and smoothing the calculated measures with an FWHM of 20 mm to ensure differences are shown without significantly increased false-positive clusters. The resulting thickness and area maps of each individual were transformed to a common spherical coordinate system. 2.4 Statistical Analysis Vertex-wise cortical surface group analysis was performed by two-class general linear model (GLM).The GLM was used to estimate the time series image parameters, and then through the random effects analysis, obtain statistical parametric mapping. The stimulus pattern function of hemodynamic function after convolution as design matrix parameters are estimated through the design matrix, then the statistical test of specific parameters, draw each voxel values t.The statistical analysis for cortical surface thickness and area was

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performed by the QDEC interface of Freesurfer.The SPSS17.0 (SPSS Inc. Chicago, IL, USA) statistical analysis software package was used in the study.Normality test was performed for each group of data,under the premise of satisfying the normal distribution,the data in the

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group were tested by double sample t. Group analysis is remove the age, sex, and the mean of the whole brain signal of the 2 groups.The statistical threshold is set to the corrected P≤ 0.05, False discovery rate (FDR) with the threshold of p < 0.05 was used to regions that

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displayed differences in metric distortion to correct for multiple comparisons.

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3. Results

3.1 Cortical Thickness Comparison

Comprehensive brain analysis for cortical thickness revealed widespread regions with

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significantly greater metric in the Uyghurs compared with Han Chinese (Fig. 1A-D). On the lateral surface of the cerebral cortex, these regions mainly located in the bilateral superior

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frontal, rostral middle frontal, pars triangularis, pars opercularis, middle temporal, supramarginal, superior parietal, inferior parietal, and the lower part of pre- and postcentral

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gyrus (namely the Rolandic operculum). Different regions on the medial cerebral cortical surface mainly included the left caudal anterior cingulate and the posterior cingulate gyrus.

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Generally, the left hemisphere was detected with more widespread area with significant difference. No region was thicker in Han Chinese. Details on overlaid brain areas were summarized in Table 2. Notably, significant areas showed a tendency of convergence in the supra-sylvian regions (namely fronto-parietal operculum) in both hemispheres (Fig. 3A, B). Besides, our results showed strong resemblance in terms of distribution of different regions compared with findings of previous cortical thickness study between Asians and Westerners (Chee et al., 2011) (Fig. 1E-H). 3.2 Surface Area Comparison Cortical surface area analysis displayed less widespread but more right-hemisphere distributed differences, compared with the regions with cortical thickness differences. Only

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three clusters showed significantly increased surface area in Han Chinese located in the boundary region of the left caudal middle frontal and precentral gyrus, the left middle temporal gyrus, and the boundary region of the left superior parietal and lateral occipital

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gyrus (Fig. 2A, C). Comparatively wider regions with different surface area were found in the right hemisphere mainly including the right pars opercularis and triangularis gyrus, the right Rolandic operculum, the right middle temporal gyrus, and the right lateral occipital

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gyrus (Fig. 2B, D). Converged regions with significant different surface area in the fronto-parietal operculum were also observed in the right hemisphere (Fig. 3C), but not

4. Discussion

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4.1 Subject Selection Strategy

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evident in the left hemisphere. Details on overlaid brain areas were summarized in Table 2.

Compared with previous studies, the volunteers we recruited in this study were from two

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more genetically specific populations – the Uyghur and Han Chinese. Both of the two ethnic groups are from China with at least 400 years of history and basically conserve different

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cultures, languages, and life styles. By contrast, previous studied subjects were roughly classified as “Black vs. White race categories” (Kubota et al., 2012), “East Asians vs.

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Westerners” (Chee et al., 2011) or “Europeans vs. Japanese” (Zilles et al., 2001) etc, and the subjects’ ethnic/family backgrounds were not fully investigated. Therefore, the grouping strategy adopted in our study will help to purify subjects’ genetic origin. Moreover, all the subjects included are young college undergraduates. Firstly, educational backgrounds can be soundly matched in this manner. Secondly, evidence from both behavioral and structural imaging studies (Chee et al., 2011; Park et al., 1999) supports that interethnic neurobiological differences probably decline with age and leading to more similarity in cognitive function in late adulthood, e.g. in Chee’s study (Chee et al., 2011), significantly different cortical thickness was found in multiple regions including BA 45, 47, 10, 9, 8, 7 etc. between young participants from Singapore and United States, while smaller difference (only left inferior temporal gyrus) was identified between old participants. Therefore, in our current study we recruited young individuals with small age variation (18.3±0.5 and

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18.4±0.7) to magnify the inherent interethnic differences between Uyghurs and Han Chinese.

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4.2 Comparison with Previous “Eastern vs. Western” Structural Studies

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In this “Eurasians vs. Asians” study, our results showed strong resemblance in terms of distribution of regions with difference, compared with findings of previous “Eastern vs.

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Western” studies. In the five previous studies, two mainly focused on cross-linguistic driven effect (Crinion et al., 2009; Green et al., 2007) and defined the increased gray matter density

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in the right anterior temporal and the left insula regions as a neuroanatomical marker for speaking Chinese; one focused on variability in hemispheric shape (Zilles et al., 2001) and addressed large scale differences in the occipital and temporal lobe; the rest two provided region-to-region comparisons of brain structure between two ethnic groups (Chee et al.,

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2011; Kochunov et al., 2003). Chee’s study applied similar method and investigated subjects in similar age with ours and analyzed cortical thickness, so here we make a detailed

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comparison.

In Chee’s study (Chee et al., 2011), significantly greater cortical thickness was detected

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mainly in the bilateral precuneus and inferior (including pars triangularis and part of rostral middle frontal gyrus) and superior frontal gyrus, the left precentral gyrus, and the right

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superior parietal gyrus, medial-temporal region, and supramarginal gyrus with part of the angular gyrus of young American participants, while only the left inferior temporal gyrus showed thicker cortex in young Chinese Singaporeans. So, compared with the previous findings, most of our currently detected regions with significant difference are convergent (including the corresponding areas on different side) except for the left cingulate gyrus (the caudal anterior cingulate and posterior cingulate gyrus) and the bilateral postcentral gyrus. Generally speaking, most of the regions showing different cortical thickness between Han Chinese and Uyghurs can also be found in corresponding brain areas between Westerners and Easterners (Fig. 1), and both Uyghurs and Westerners show generally thicker cortical thickness compared with Chinese. While the distribution of these Han – Uyghur different regions tends to be less widespread and more left lateralized comparatively. It is a pity that surface area analysis was not applied in previous studies. In spite of this,

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we found previous evidence in line with our findings. Zilles found that European brains showed an outbending of the hemispheric surface in the occipital pole compared with Japanese’s, which means the later are shorter but wider (Zilles et al., 2001). This finding is

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in line with the greater surface area of Han Chinese brain in the bilateral occipital regions revealed in our study. Furthermore, we found much less widespread area with different surface area than that with cortical thickness difference in this study. Since cortical surface

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area tends to detect more genetic-related information while cortical thickness reflects more postnatal differences caused brain structure alterations, our findings further supports

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previous argument that experience-related effects probably exceed those of inherited/genetic factors on brain structure alteration (Chee et al., 2011; Kochunov et al., 2003). 4.3 Findings of Characteristic

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In this study, the most characterized finding of brain structural differences between Uyghurs and Han Chinese perhaps lies in the fronto-parietal operculum, where both cortical thickness

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and surface area analyses showed significance. To highlight this finding, we further set a threshold of p = 0.001 (uncorrected) to generate a new set of statistical maps (Fig.3).

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Compared with other regions, this region survived better, and the trend is more evident in right hemisphere. While its exact mechanism and relation to interethnic differences may

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need to be further investigated, since the functional role of the fronto-parietal operculum regions is fairly complex and includes a wide range (e.g., visual motion (Antal et al., 2008), somatosensory stimuli processing (Stancak et al., 2005), production (Tonkonogy and Goodglass 1981) and prosody perception (Hoekert et al., 2008) of language, et al.). Besides, other regions with differences, which were not identified in previous Westerners vs. Asians studies, include the left cingulate gyrus and the left postcentral gyrus. An almost whole-region wide thicker cortex is shown in both of the two areas (Fig. 1A, C), thus they may also be of some characteristic. 4.4 Cross-linguistic Driven Effect In many studies , the results of the Chinese and Western text almost unanimously found most right-handed adults in complete language tasks, the left hemisphere has stronger

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activation.Through comparing the activating quantity of left-right hemisphere and interested regions,the function of language advantage has been demonstrated in the left hemisphere.Our results are similar,all the subjects were right-handed and the left hemisphere

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detected in the wider region have significant differences in our study.Several classic cerebral language centers are found to show different cortical thickness between Han Chinese and Uyghurs including the bilateral pars triangularis (BA 45) and pars opercularis (BA 44), the

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supramarginal gyrus (BA 40), and the middle temporal gyrus (BA 21). In addition, Han Chinese suggest increased surface area in the bilateral middle temporal gyrus, and the

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anterior portion of left middle temporal gyrus is identified as a characterized different region between Chinese speaker and English speaker supported by both functional and structural evidences (Kochunov et al., 2003; Tan et al., 2003). In terms of function, the BA 44 and 45 are well renowned as Broca’s area being responsible for language expression, narratives,

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and local visual searching (Craighero et al., 2007; Horwitz et al., 2003); BA 40, part of another classic cerebral language center – Wernicke's area, its increased activation is

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identified when participants focused on the sound of a word according to the visual word recognition studies (Demonet et al., 1994; Devlin et al., 2003); BA 21 which involves

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selective processing of text and speech (Giraud et al., 2004), semantic processing (Chou et al., 2006), word generation (Friedman et al., 1998) and sentence generation (Brown et al.,

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2006), is believed to play a role in auditory and language processing as well. Besides that, the left insular cortex (BA 13) indicated to be involved in Chinese words and “tone” processing by Mandarin speakers (Crinion et al., 2009; Dietrich et al., 2008; Wong et al., 2004) also suggests different cortical thickness in our study. To reiterate, our detected regions with structural difference between Uyghurs and Han Chinese contain a large part of language-specific or at least closely language-related brain areas. Thus, our findings may partly be attributable to the anatomical plasticity respectively driven by Uyghur and Mandarin. Moreover, this hypothesis is further reinforced by our findings of “left lateralized differences” since language function is left lateralized in most individuals. Previous studies, even including cross-ethnic studies, put much emphasis on the cross-linguistic driven effect on brain structure alteration (Crinion et al., 2009; Green et al., 2007; Kochunov et al., 2003; Mechelli et al., 2004). For instance, different grey matter

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density in right anterior temporal lobe and the left insula is shown not only between Chinese and European multilinguals (excluding Chinese), but also within the same regions between native English speakers with Chinese proficiency and those European multilinguals (Crinion

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et al., 2009), which suggests that detected different grey matter density is caused by speaking Chinese. Moreover, bilinguals (European or Chinese) are related to increased grey matter density in the posterior supramarginal parietal region (Mechelli et al., 2004). This

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language-driven brain alteration is probably attributable to the widely accepted adaptation-driven anatomical plasticity theory supported by both microscopic (Landing et al.,

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2002) and macroscopic evidences from the studies on handedness (Amunts et al., 2000; Foundas et al., 1998), musical training (Amunts et al., 1997) etc. Language is also believed to be a valid factor since it is extensively practiced throughout childhood (Kochunov et al., 2003).

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4.5 Limitations and Future Work

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Firstly, although we’ve proved brain structural differences between the two ethnic groups of Han Chinese and Uyghur to be detectable by MRI, yet more significance and interest may

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be attached to how these differences may relate to type of cognitions or social behaviors (e.g. real-world decision-making and its consequential effects for social or personal changes

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(Kubota et al., 2012)). It is a pity that the available cognitive and behavioral studies on Uyghur in literatures are so scarce that we have difficulty in establishing a valid neuroimaging-to-cognition/behavior relevance in the current study. However, our findings will help to provide evidences of neurobiological basis for future cognitive/behavioral studies on Uyghur. Secondly, although we’ve identified structural difference in several language-related brain areas and hypothetically concluded the cross-linguistic driven effect to be responsible, functional studies are needed not only to provide direct evidence for confirming the causal relationship between the language difference and functional brain difference (e.g. different activation models), but also to further analyze and compare the different neural mechanisms of language processing between Uyghur and Mandarin under different categories or natures of language processing tasks (e.g. tasks in semantic level, orthographic level, phonologic level etc.). Thirdly, we only recruited young individuals as

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the subjects. Previous findings suggest that language processing begins in early infancy stage when language abilities acquired are of no ethnical specificity (MacNeilage and Davis 2000; Petitto et al., 2001). So, if the differences in language-related brain regions defined in

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our study are found to be insignificant in early infancy, we’ll have more reason to believe the cross-linguistic driven effect is responsible for part of our current findings. Moreover, to enhance the stability and statistical power of the results, a larger subject size will be

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recruited in the future for further study of this matter.

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Conclusion

In this study, we compared the cortical thickness and surface area between young Uyghurs and Han Chinese, and found that differences in brains structure between the two genetic-related ethnic groups are detectable by structural imaging method. Compared with

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findings of previous “Eastern vs. Western” studies, our results showed strong resemblance in terms of distribution of regions with structural difference. A tendency of convergence of

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regions with difference in the fronto-parietal operculum regions may be of some features. Since our identified regions contain a large part of language-specific or at least closely

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language-related areas, we hypothetically attribute our findings to the brain’s

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adaption-driven anatomical plasticity by cross-linguistic driven effect partly. This study will help to shed light on the neurobiological basis for interethnic differences between Uyghur and Han Chinese for further cognitive/behavioral studies. In addition, our findings will provide evidences for the construction of ethnic-specific brain templates for further neuroimaging studies on Uyghur.

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Figure Legends

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Fig. 1. A-D, statistical maps of cortical thickness difference for left (A, C) and right hemisphere (B, D) between Han Chinese and Uyghurs. Vertices colorized in the figure indicate a statistical significance (false discovery rate; 0.05). Uyghurs suggest widespread regions with greater cortical thickness compared with Han Chinese. E-H, cited from (Chee et al., 2011), statistical maps of cortical thickness difference between United States young (U.S.) and Singapore young (SG) subjects. Regions in red mean U.S. group has higher thickness than the SG group.

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Fig. 2. Statistical maps of cortical surface area difference for left (A, C) and right hemisphere (B, D) between Han Chinese and Uyghurs. Vertices colorized in red indicate significantly greater surface area in Han Chinese (false discovery rate; 0.05).

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Fig. 3. Statistical maps of differences in cortical thickness (A, left hemisphere; B, right hemisphere) and cortical surface area (C, right hemisphere) were thresholded at p = 0.001 (uncorrected) to highlight the significance in supra-sylvian regions (in white cycles).

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Figure 1

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Figure 2

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ACCEPTED MANUSCRIPT 21 Table 1. Demographic details of Han Chinese and Uyghurs. Han Chinese

n

15

15

Age

18.3±0.5

18.4±0.7

Gender (female/male)

8/7

7/8

Education years

13

13

Handedness (right/left)

15/0

15/0

Listening

97.6±2.2

98.9±1.5

Naming

99.7±0.9

99.8±0.6

Repetition

96.1±1.2

99.2±1.6

Reading and comprehension

99.0±2.1

99.3±1.8

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Uyghur

ACCEPTED MANUSCRIPT 22 Table 2. Comparison of cortical thickness and surface area between Han Chinese and Uyghurs Thickness LH

RH

+ + + + + + + + + + + + + + + + + +

+

LH

RH

T

-

RI P

+

-

+ + + + + + + + + + + + + +

SC

-

-

-

-

-

-

-

-

PT

ED

Lateral cerebral Superior frontal Frontal pole Rostral middle frontal Caudal middle frontal Pars opercularis Pars triangularis Lateral orbitofrontal Pars orbitalis Precentral Postcentral Superior parietal Inferior parietal Supramarginal Superior temporal Middle temporal Inferior temporal Lateral occipital Insula

Surface Area

MA NU

Anatomical Area

AC

CE

Medial cerebral Medial orbitofrontal Caudal anterior cingulate Posterior cingulate Paracentral Precuneus Lingual

+ + + + + +

+

-

LH = left hemisphere; RH = right hemisphere; “+” = metric being greater in Uyghurs; “-” = metric being greater in Han Chinese; “blank” = no significant difference.