Philipps-University Marburg, Center of Brain Imaging, Department of Neurology, Marburg, Germany.
Neuroimage. 2011 Feb 14;54(4):2557-62. doi: 10.1016/j.neuroimage.2010.11.029. Epub 2010 Nov 16.
Numerous magnetic resonance imaging (MRI) studies have addressed the question of morphological differences of the brain of men and women, reporting conflicting results regarding brain size and the ratio of gray and white matter. In the present study, we used diffusion tensor imaging (DTI) to delineate sex differences of brain white matter.
We investigated brain microstructure in 25 male and 25 female healthy subjects using a 3T MRI scanner. Whole-head DTI scans were analyzed without a-priori hypothesis using Tract-Based Spatial Statistics (TBSS) calculating maps of fractional anisotropy (FA), radial diffusivity (RD, a potential marker of glial alteration and changes in myelination) and axial diffusivity (AD, a potential marker of axonal changes).
DTI revealed regional microstructural differences between the brains of male and female subjects. Those were prominent in the thalamus, corpus callosum and cingulum. Men showed significantly (p<0.0001) higher values of fractional anisotropy and lower radial diffusivity in these areas, suggesting that the observed differences are mainly due to differences in myelination.
As a novel finding we showed widespread differences in thalamic microstructure that have not been described previously. Additionally, the present study confirmed earlier DTI studies focusing on sexual dimorphism in the corpus callosum and cingulum. All changes appear to be based on differences in myelination. The sex differences in thalamic microstructure call for further studies on the underlying cause and the behavioral correlates of this sexual dimorphism. Future DTI group studies may carefully control for gender to avoid confounding.
许多磁共振成像（MRI）研究已经解决了男性和女性大脑形态差异的问题，报告了关于大脑大小和灰质与白质比例的相互矛盾的结果。在本研究中，我们使用弥散张量成像（DTI）来描绘大脑白质的性别差异。
我们使用 3T MRI 扫描仪对 25 名男性和 25 名女性健康受试者的大脑微观结构进行了研究。全脑 DTI 扫描是在没有先验假设的情况下使用基于体素的空间统计学（TBSS）进行分析的，计算了各向异性分数（FA）、径向弥散度（RD，胶质改变和髓鞘变化的潜在标志物）和轴向弥散度（AD，轴突变化的潜在标志物）的图谱。
DTI 显示了男性和女性受试者大脑之间的区域微观结构差异。这些差异在丘脑、胼胝体和扣带中尤为明显。男性在这些区域的分数各向异性显著（p<0.0001）更高，而径向弥散度更低，这表明观察到的差异主要是由于髓鞘差异所致。
作为一个新的发现，我们显示了在丘脑微观结构中存在广泛的差异，这些差异以前没有被描述过。此外，本研究还证实了以前关于胼胝体和扣带性别二态性的 DTI 研究。所有的变化似乎都基于髓鞘的差异。丘脑微观结构的性别差异需要进一步研究其潜在原因及其与这种性别二态性的行为相关性。未来的 DTI 组研究可能需要仔细控制性别，以避免混淆。
