Hofer Sabine, Frahm Jens
Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, 37070 Göttingen, Germany.
Neuroimage. 2006 Sep;32(3):989-94. doi: 10.1016/j.neuroimage.2006.05.044. Epub 2006 Jul 18.
Several tracing studies have established a topographical distribution of fiber connections to the cortex in midsagittal cross-sections of the corpus callosum (CC). The most prominent example is Witelson's scheme, which defines five vertical partitions mainly based on primate data. Conventional MRI of the human CC does not reveal morphologically discernable structures, although microscopy techniques identified myelinated axons with a relatively small diameter in the anterior and posterior third of the CC as opposed to thick fibers in the midbody and posterior splenium. Here, we applied diffusion tensor imaging (DTI) in conjunction with a tract-tracing algorithm to gain cortical connectivity information of the CC in individual subjects. With DTI-based tractography, we distinguished five vertical segments of the CC, containing fibers projecting into prefrontal, premotor (and supplementary motor), primary motor, and primary sensory areas as well as into parietal, temporal, and occipital cortical areas. Striking differences to Witelson's classification were recognized in the midbody and anterior third of the CC. In particular, callosal motor fiber bundles were found to cross the CC in a much more posterior location than previously indicated. Differences in water mobility were found to be in qualitative agreement with differences in the microstructure of transcallosal fibers yielding the highest anisotropy in posterior regions of the CC. The lowest anisotropy was observed in compartments assigned to motor and sensory cortical areas. In conclusion, DTI-based fiber tractography of healthy human subjects suggests a modification of the widely accepted Witelson scheme and a new classification of vertical CC partitions.
多项追踪研究已确定了胼胝体（CC）矢状中截面与皮质之间纤维连接的拓扑分布。最突出的例子是威特elson的方案，该方案主要基于灵长类动物数据定义了五个垂直分区。人类CC的传统MRI并未显示出形态上可辨别的结构，尽管显微镜技术发现CC前后三分之一处有直径相对较小的有髓轴突，而胼胝体中部和压部后部则是粗纤维。在此，我们将扩散张量成像（DTI）与一种示踪算法相结合，以获取个体受试者CC的皮质连接信息。基于DTI的纤维束成像，我们区分了CC的五个垂直段，其中包含投射到前额叶、运动前区（和辅助运动区）、初级运动区、初级感觉区以及顶叶、颞叶和枕叶皮质区的纤维。在CC的中部和前三分之一处发现了与威特elson分类的显著差异。特别是，胼胝体运动纤维束交叉CC的位置比之前指出的要靠后得多。发现水流动性的差异与胼胝体纤维微观结构的差异在质量上一致，CC后部区域的各向异性最高。在分配给运动和感觉皮质区的区域中观察到最低的各向异性。总之，基于DTI的健康人类受试者纤维束成像表明，需要对广泛接受的威特elson方案进行修改，并对CC垂直分区进行新的分类。
