Laboratory of Neuro Imaging, Department of Neurology, UCLA School of Medicine, Los Angeles, CA, USA.
Neuroimage. 2010 Aug 15;52(2):455-69. doi: 10.1016/j.neuroimage.2010.04.236. Epub 2010 Apr 27.
Brain asymmetry, or the structural and functional specialization of each brain hemisphere, has fascinated neuroscientists for over a century. Even so, genetic and environmental factors that influence brain asymmetry are largely unknown. Diffusion tensor imaging (DTI) now allows asymmetry to be studied at a microscopic scale by examining differences in fiber characteristics across hemispheres rather than differences in structure shapes and volumes. Here we analyzed 4Tesla DTI scans from 374 healthy adults, including 60 monozygotic twin pairs, 45 same-sex dizygotic pairs, and 164 mixed-sex DZ twins and their siblings; mean age: 24.4years+/-1.9 SD). All DTI scans were nonlinearly aligned to a geometrically-symmetric, population-based image template. We computed voxel-wise maps of significant asymmetries (left/right differences) for common diffusion measures that reflect fiber integrity (fractional and geodesic anisotropy; FA, GA and mean diffusivity, MD). In quantitative genetic models computed from all same-sex twin pairs (N=210 subjects), genetic factors accounted for 33% of the variance in asymmetry for the inferior fronto-occipital fasciculus, 37% for the anterior thalamic radiation, and 20% for the forceps major and uncinate fasciculus (all L>R). Shared environmental factors accounted for around 15% of the variance in asymmetry for the cortico-spinal tract (R>L) and about 10% for the forceps minor (L>R). Sex differences in asymmetry (men>women) were significant, and were greatest in regions with prominent FA asymmetries. These maps identify heritable DTI-derived features, and may empower genome-wide searches for genetic polymorphisms that influence brain asymmetry.
脑偏侧性，即每个大脑半球的结构和功能特化，一个多世纪以来一直令神经科学家着迷。即便如此，影响大脑偏侧性的遗传和环境因素在很大程度上仍是未知的。弥散张量成像（DTI）现在可以通过检查大脑半球之间纤维特征的差异而不是结构形状和体积的差异，在微观尺度上研究偏侧性。在这里，我们分析了来自 374 名健康成年人的 4Tesla DTI 扫描，包括 60 对同卵双胞胎、45 对同性别异卵双胞胎和 164 对混合性别 DZ 双胞胎及其兄弟姐妹；平均年龄：24.4 岁+/-1.9 SD）。所有 DTI 扫描均以非线性方式与基于几何对称的人群图像模板对齐。我们计算了反映纤维完整性的常见扩散测量值（分数各向异性和测地各向异性；FA、GA 和平均扩散率，MD）的显著偏侧性（左右差异）的体素映射。在从所有同性别双胞胎（N=210 名受试者）计算的定量遗传模型中，遗传因素解释了下额枕束的偏侧性变异的 33%，前丘脑辐射的 37%，以及钩束和上纵束的 20%（均为 L>R）。共享环境因素解释了皮质脊髓束（R>L）偏侧性变异的约 15%，以及钩束的约 10%（L>R）。偏侧性的性别差异（男性>女性）显著，在 FA 偏侧性明显的区域最大。这些图谱确定了可遗传的 DTI 衍生特征，并且可能有助于全基因组搜索影响大脑偏侧性的遗传多态性。
