The nerve fibers are divided into three categories: projection, commissural, and association fibers. This study demonstrated a novel cortical mapping method based on these three fiber categories using MR tractography data. The MR fiber-track data were extracted using the diffusion-weighted 3T-MRI data from the 19 individuals Human Connectome Project dataset. Anatomical MR images in each dataset were parcellated using FreeSurfer software and Brainnetome atlas. The 5million extracted tracks per subject by MRtrix software were classified based on the basic cortical structure (cortical area in the left and right hemisphere, subcortical area), after the tracks validation procedure. The number of terminals for each categorized tracks per unit-sized cortical area (1mm3) was defined as the track-density in that cortical area. Track-density ratio mapping with fiber types was achieved by mapping the density-dependent color intensity for each categorized tracks with a different primary color. The mapping results showed a highly localized, unique density ratio map determined by fiber types. Furthermore, the quantitative group data analysis based on the parcellation information revealed that the majority of nerve fibers in the brain are association fibers, particularly in temporal, inferior parietal, and occipital lobes, while the projection and commissural fibers were mainly located in the superior part of the brain. Hemispheric asymmetries in the fiber density were also observed, such as long association fiber in the Broca’s and Wernicke’s areas. We believe this new dimensional brain mapping information allows us to further understand brain anatomy, function.

中文翻译：

---

使用弥散加权 MRI 绘制大脑皮层纤维类型的磁道密度比图

神经纤维分为三类：投射纤维、连合纤维和联合纤维。本研究使用 MR 纤维束成像数据展示了一种基于这三种纤维类别的新型皮层映射方法。使用来自 19 个个体人类连接组项目数据集的扩散加权 3T-MRI 数据提取 MR 纤维轨迹数据。使用 FreeSurfer 软件和 Brainnetome 图谱对每个数据集中的解剖 MR 图像进行分割。在轨迹验证程序之后，MRtrix 软件根据基本皮质结构（左右半球的皮质区域，皮质下区域）对每个受试者提取的 500 万条轨迹进行分类。每单位大小的皮质区域（1mm3）的每个分类轨道的终端数量定义为该皮质区域的轨道密度。通过映射具有不同原色的每个分类轨道的密度相关颜色强度来实现纤维类型的轨道密度比映射。映射结果显示了由纤维类型决定的高度局部化、独特的密度比图。此外，基于分割信息的定量组数据分析表明，大脑中的大部分神经纤维是联合纤维，尤其是在颞叶、下顶叶和枕叶，而投影和连合纤维主要位于上部的大脑。还观察到纤维密度的半球不对称性，例如布洛卡区和韦尼克区的长关联纤维。我们相信这种新的维度大脑映射信息使我们能够进一步了解大脑的解剖结构、功能。