Luders Eileen, Gaser Christian, Narr Katherine L, Toga Arthur W
Laboratory of Neuro Imaging, Department of Neurology, School of Medicine, University of California, Los Angeles, Los Angeles, California 90095-7334, USA.
J Neurosci. 2009 Nov 11;29(45):14265-70. doi: 10.1523/JNEUROSCI.2261-09.2009.
The different brain anatomy of men and women is both a classic and continuing topic of major interest. Among the most replicated and robust sex differences are larger overall brain dimensions in men, and relative increases of global and regional gray matter (GM) in women. However, the question remains whether sex-typical differences in brain size (i.e., larger male and smaller female brains) or biological sex itself account for the observed sex effects on tissue amount and distribution. Exploring cerebral structures in men and women with similar brain size may clarify the true contribution of biological sex. We thus examined a sample of 24 male and 24 female subjects with brains identical in size, in addition to 24 male and 24 female subjects with considerable brain size differences. Using this large set of brains (n = 96), we applied a well validated and automated voxel-based approach to examine regional volumes of GM. While we revealed significant main effects of sex, there were no significant effects of brain size (and no significant interactions between sex and brain size). When conducting post hoc tests, we revealed a number of regions where women had larger GM volumes than men. Importantly, these sex effects remained evident when comparing men and women with the same brain size. Altogether, our findings suggest that the observed increased regional GM volumes in female brains constitute sex-dependent redistributions of tissue volume, rather than individual adjustments attributable to brain size.
男性和女性不同的大脑解剖结构一直是一个经典且持续受到关注的重要话题。在最具重复性和稳定性的性别差异中，男性的大脑整体尺寸更大，而女性的大脑全局和区域灰质（GM）相对增加。然而，问题仍然存在：大脑大小的性别典型差异（即男性大脑较大，女性大脑较小）还是生物性别本身导致了观察到的性别对脑组织数量和分布的影响。研究大脑大小相似的男性和女性的脑结构可能会阐明生物性别的真正作用。因此我们除了研究24名大脑大小差异显著的男性和24名女性受试者外，还研究了24名大脑大小相同的男性和24名女性受试者。利用这一大组大脑样本（n = 96），我们采用了一种经过充分验证的基于体素的自动化方法来检查灰质的区域体积。虽然我们发现了显著的性别主效应，但没有发现大脑大小的显著效应（以及性别和大脑大小之间没有显著的交互作用）。在进行事后检验时，我们发现了一些女性灰质体积大于男性的区域。重要的是，当比较大脑大小相同的男性和女性时，这些性别效应仍然明显。总之，我们的研究结果表明，观察到女性大脑中区域灰质体积增加是脑组织体积按性别分布的结果，而不是因大脑大小导致的个体差异。
