Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA 94143-0628, USA.
Neuroimage. 2010 Jun;51(2):531-41. doi: 10.1016/j.neuroimage.2010.02.072. Epub 2010 Mar 4.
The purpose of this study is to investigate whether specific patterns of correlation exist in diffusion tensor imaging (DTI) parameters across different white matter tracts in the normal human brain, and whether the relative strengths of these putative microstructural correlations might reflect phylogenetic and functional similarities between tracts. We performed quantitative DTI fiber tracking on 44 healthy adult volunteers to obtain tract-based measures of mean diffusivity (MD), fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) from four homologous pairs of neocortical association pathways (arcuate fasciculi, inferior fronto-occipital fasciculi, inferior longitudinal fasciculi, and uncinate fasciculi bilaterally), a homologous pair of limbic association pathways (left and right dorsal cingulum bundles), and a homologous pair of cortical-subcortical projection pathways (left and right corticospinal tracts). From the resulting inter-tract correlation matrices, we show that there are statistically significant correlations of DTI parameters between tracts, and that there are statistically significant variations among these inter-tract correlations. Furthermore, we observe that many, but by no means all, of the strongest correlations are between homologous tracts in the left and right hemispheres. Even among homologous pairs of tracts, there are wide variations in the degree of coupling. Finally, we generate a data-driven hierarchical clustering of the fiber pathways based on pairwise FA correlations to demonstrate that the neocortical association pathways tend to group separately from the limbic pathways at trend-level statistical significance, and that the projection pathways of the left and right corticospinal tracts comprise the most distant outgroup with high confidence (p<0.01). Hence, specific patterns of microstructural correlation exist between tracts and may reflect phylogenetic and functional similarities between tracts. The study of these microstructural relationships between white matter pathways might aid research on the genetic basis and on the behavioral effects of axonal connectivity, as well as provide a revealing new perspective with which to investigate neurological and psychiatric disorders.
本研究旨在探究正常人类大脑不同白质束之间弥散张量成像（DTI）参数是否存在特定的相关模式，以及这些潜在的微观结构相关性的相对强度是否反映了束之间的系统发育和功能相似性。我们对 44 名健康成年志愿者进行了定量 DTI 纤维追踪，以从四个同源对的新皮质联络束（弓状束、下额枕束、下纵束和钩束）、一对同源的边缘联络束（左和右背扣带束）以及一对同源的皮质-皮质下投射束（左和右皮质脊髓束）中获得基于束的平均弥散度（MD）、分数各向异性（FA）、轴向弥散度（AD）和径向弥散度（RD）的测量值。从得到的束间相关矩阵中，我们发现束之间的 DTI 参数存在具有统计学意义的相关性，并且这些束间相关性存在显著差异。此外，我们观察到许多，但并非所有最强的相关性都是在左右半球的同源束之间。即使是在同源束对中，耦合程度也有很大差异。最后，我们根据 FA 相关性生成了一个纤维束的基于数据驱动的层次聚类，以证明新皮质联络束在趋势水平上显著地与边缘束分离，并且左、右皮质脊髓束的投射束构成了最遥远的异群，置信度很高（p<0.01）。因此，束之间存在特定的微观结构相关性，这可能反映了束之间的系统发育和功能相似性。对这些白质束之间的微观结构关系的研究可能有助于研究轴突连接的遗传基础和行为影响，并提供一个新的视角来研究神经和精神障碍。
