brain development difference chinese and whites

This study compared head and structural brain development of Chinese children and adolescents with American age-related children and adolescents. The brains and heads of Chinese participants showed differences in morphological features (e.g., length, width, and height) compared with their American counterparts. Overall, Chinese children's brains and heads were shorter, wider, and taller than U.S. children's. The total head, intracranial, and cerebral volumes showed different patterns of change over age for the Chinese and U.S. children. Total head volume showed a linear increase with age for both Chinese and U.S. children, but U.S. children revealed a steeper slope than Chinese children. Intracranial and total brain volume showed an inverted U-shaped pattern for Chinese and U.S. children, but peaked at different ages. The overall volume of both GM and WM had similar developmental trajectories for Chinese and U.S. children, with some differences in the peak of the inverted-U function for the two nationalities. Regional GM comparisons showed differences in developmental patterns and volume between the two nationalities for the temporal and occipital lobes, while those for the frontal and parietal lobes were more similar between the nationalities. Finally, our detailed comparisons of 50 LPBA40 cortical structures between Chinese and U.S. children showed regional differences in both brain volume and developmental patterns.

Brain and head morphometric measurements confirmed our first hypothesis that Chinese and U.S. children and adolescents would be different in brain and head shape, size, and developmental patterns. These findings were consistent with results from comparisons of head and brain structures in Asian and North American adults (Lee et al., 2005; Tang et al., 2010). Specifically, Chinese children's brains were shorter, wider, and taller than age-related U.S. children, which mirror findings from direct comparisons of Chinese and North American adult brains (Tang et al., 2010). We did not find differences in the AC-PC distance between Chinese and U.S. children and adolescents, which we expected based on results reported by Tang et al. (2010). Perhaps the developmental patterns of the AC-PC distance in the two populations diverge after adolescence. The developmental trajectory of brain height was different between these two nationalities, while brain and head length and width showed similar developmental patterns. Future studies may investigate these features in younger children or even infants to better understand when these trajectories start to diverge. Differences in brain and head morphological features and developmental patterns between Chinese and U.S. children may be due to tissue level differences inside the brain.

Our results showed that global head volume increased linearly for both Chinese and U.S. children, but at different rates. The patterns of head volume development (Figure ​(Figure3)3) were quite similar with those of head length development (Figure ​(Figure2).2). The greater head volume found in the U.S. children might be due to their longer head length. Gender was also a factor: both Chinese and U.S. males showed greater head volumes than females. Chinese and American children showed different patterns of intracranial volume development; however, these patterns differed with those of head volume development. Chinese children showed larger intracranial volumes than U.S. cohorts, and males showed larger volumes than females. This dissociation may be caused by differences in the developmental trajectories of brain tissue (GM, WM, CSF) between these two populations. Since head volume includes other tissues (e.g., bones, skull), intracranial volume may be more informative in predicting brain development.

Our volumetric measurements of brain volume, GM, and WM development indicated that there are similarities and differences between Chinese and U.S. children's brain development. The global effects of age found in Chinese and U.S. participants were consistent with previous volumetric studies with Chinese and U.S. children (Giedd et al., 1996b, 1999; Guo et al., 2007; Lenroot et al., 2007). Specifically, our finding that the development of total cerebral volume followed an inverted U-shape for Chinese children peaking at early adolescence was consistent with previous findings with U.S. children (Lenroot et al., 2007). Chinese children's GM (inverted U) and WM (linear) developmental patterns (Figure ​(Figure4)4) are similar to the findings for U.S. children reported in this study and previous research (Giedd et al., 1999; Lenroot et al., 2007). One difference regarding the patterns of the GM development is that GM development in the Chinese children peaked later than the U.S. children. No overall nationality effect was found on WM; however, there was an interaction of age and nationality on WM development, such that U.S. children had larger WM volume than Chinese children after 10 years of age. Our findings for cortical GM and WM development mostly mirror the patterns of overall GM and WM development, such that age and nationality affect the development of the cerebral cortex. The patterns of global GM and cortical GM development are more consistent with intracranial and brain volume development than WM development. One possible explanation is that due to the overall greater proportion of GM than WM proportion in the brain (see Figure ​Figure4),4), GM development has a stronger influence on children's brain developmental patterns. This may also explain why Chinese children had larger GM but smaller WM volumes than U.S. children and had larger intracranial volumes than U.S. cohorts.

The growth of brain lobes in Chinese children was partially comparable with that of North American children. Chinese temporal lobe GM development pattern mirrored previous findings from U.S. children, with linear increases from childhood (8 years) to adolescence (16 years). Parietal lobe GM development in Chinese children showed an overall reduction from childhood to adolescence, which is also consistent with previous findings from U.S. (Giedd et al., 1999) and Chinese children (Guo et al., 2007). Frontal GM development showed a linear decline in Chinese children, which is inconsistent with previous studies that reported nonlinear developmental patterns peaking around puberty in U.S. children (Giedd et al., 1999; Lenroot et al., 2007). Our U.S. participants failed to show clear patterns of temporal and parietal lobe GM development. A possible cause for this is the uneven number of male and female participants. The finding that Chinese children have higher levels of GM in temporal and occipital regions than American children may be the reason why Chinese children were found to have greater total brain volume and cortical GM volume than U.S. children.

Finally, we compared 50 cortical structures segmented using the LONI Probabilistic Brain Atlas (LPBA40, Shattuck et al., 2008). Volumetric comparisons between Chinese and U.S. children showed that more than half (30/50) of these brain structures were significantly different (p < 0.05) between Chinese and U.S. children's brains. The majority (21/30) of these distinct regions are consistent with Tang et al.'s (2010) study with adults. The gyri in the temporal, occipital, and orbitofrontal regions showed consistent differences in volume between Chinese and U.S. populations for both children and adults. Some structures (e.g., cingulate gyri, insular cortex) were not different for the Chinese and U.S. children in this study, but were different in adults (Tang et al., 2010). It is possible that some of these areas show differential growth in late adolescence or early adulthood, accounting for the differences between our data and Tang et al.'s (2010) results. The inverted U-shaped developmental patterns and different ages of peak volume for most of these brain structures are in accord with the differences seen in global GM and intracranial development between Chinese and U.S. children. Nationality had a significant effect on most of the GM volume comparisons for these 50 brain structures. These volumetric findings suggest that there is a need for population-specific (e.g., Chinese/Asian children) atlases in both structural and functional neuroimaging studies of brain structures.

We were unable to conduct an extensive examination of gender differences due to the unequal distribution of gender across age in the data of Chinese children. In the current study, we had limited numbers of female Chinese subjects for the first several age groups. Gender is an important factor in the delineation of brain structures for children and adolescents (Giedd et al., 1999; Sowell et al., 2004; Lenroot et al., 2007). Previous studies have shown that there are gender differences in brain development of U.S. children. Therefore, we would expect that future research with even number of males and females in each age might find interaction between gender, nationality, and age.

To the best of our knowledge, this study is the first that directly compares brain development between Asian and North American children. Our findings showed global and regional differences in both morphological and volumetric/anatomical brain development between the two populations. The Chinese children's brain was found to have different shape and size compared to U.S. children. Since we found many of these differences in our youngest age groups, this implies that these features already are different in younger children. Overall, Chinese children show similar global GM and WM development patterns to US children; however, Chinese children seem to have more GM but less WM (from puberty to adolescence) than US children. Measurements and comparisons for regional GM and 50 cortical structures support the detected global differences by showing detailed differences between these two populations. Both dissimilarities of genetics and environmental exposures might lead to these brain anatomical differences between Chinese and U.S. children; however, how much these factors contribute to the difference we found is unknown. Some of the brain areas that detected as being anatomically different in this study have shown robust functional differences in language processing between Chinese and Caucasian adult subjects (Kochunov et al., 2003; Kuo et al., 2003). Therefore, these anatomical differences detected between Chinese and U.S. children might lead to functional differences as well. Future research may investigate the effects of differences in brain anatomy on cognitive development (e.g., learning skills, language ability, attention, and memory development) in Chinese and American children and adolescents. Because Chinese children's brain structures mature at different rates than their American peers', they may have a different cognitive developmental trajectory, which would be an important consideration for East Asian educational systems. These anatomical differences between Chinese and U.S. children suggest the necessity for population-specific brain/head templates and atlas, and data processing and analyzing for neuroimaging research with Chinese/Asian children and adolescents.