Pfefferbaum A, Sullivan E V, Swan G E, Carmelli D
Center for Health Sciences, SRI International, 333 Ravenswood Street, Menlo Park, CA 94025, USA.
Neurobiol Aging. 2000 Jan-Feb;21(1):63-74. doi: 10.1016/s0197-4580(00)00086-5.
The midsagittal cross-sectional dimensions of the corpus callosum, the coronal cross-sectional area of the lateral ventricles at the level of the pons, and a three-dimensional estimate of intracranial volume were derived from magnetic resonance brain images obtained from 45 monozygotic and 40 dizygotic male twin pairs aged 68 to 78. Univariate genetic analyses indicated strong genetic influences contributing significantly to the variability of each brain structure. The estimated proportion of genetic variance (i.e. heritability) was 81% for intracranial volume, 79% for the midline cross-sectional area of the corpus callosum, and 79% for lateral ventricle size. There was no evidence that shared environmental influences contributed significantly to twin-pair similarities. We further used bivariate genetic modeling to estimate the genetic and environmental correlation between correlated brain structures. Intracranial volume and corpus callosum area was highly correlated, and this relationship was entirely due to shared genetic effects between these two brain structures. By contrast, the relationship between the height of the corpus callosum and the size of the lateral ventricles was due to both genetic and environmental influences in common. Corresponding genetic and environmental correlations were 0.68 and 0.58, respectively, indicating that more than half of the genetic and environmental influences on these two brain structures were shared. The manner in which the brain responds to the environment with advancing age is highly genetically determined, both for the lateral ventricles, which dilate with aging and disease, and for the corpus callosum, which is deformed in shape by age-related ventricular enlargement, whereas its midline cross-sectional area remains unchanged.
从45对68至78岁的同卵男性双胞胎和40对异卵男性双胞胎的脑部磁共振图像中，得出了胼胝体的矢状面中部横截面尺寸、脑桥水平侧脑室的冠状面横截面面积以及颅内体积的三维估计值。单变量遗传分析表明，强烈的遗传影响对每个脑结构的变异性有显著贡献。颅内体积的遗传方差估计比例（即遗传率）为81%，胼胝体中线横截面面积为79%，侧脑室大小为79%。没有证据表明共同环境影响对双胞胎对的相似性有显著贡献。我们进一步使用双变量遗传模型来估计相关脑结构之间的遗传和环境相关性。颅内体积和胼胝体面积高度相关，这种关系完全归因于这两个脑结构之间共享的遗传效应。相比之下，胼胝体高度与侧脑室大小之间的关系是由共同的遗传和环境影响造成的。相应的遗传和环境相关性分别为0.68和0.58，表明对这两个脑结构的遗传和环境影响有一半以上是共享的。随着年龄增长，大脑对环境的反应方式在很大程度上由基因决定，无论是对于随着衰老和疾病而扩张的侧脑室，还是对于因与年龄相关的脑室扩大而形状变形但其中线横截面面积保持不变的胼胝体。
