Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Division of Neuropathology, Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Neuroimage. 2015 Jan 15;105:198-207. doi: 10.1016/j.neuroimage.2014.10.053. Epub 2014 Oct 31.
Regional heterogeneity in cortical cyto- and myeloarchitecture forms the structural basis of mapping of cortical areas in the human brain. In this study, we investigate the potential of diffusion MRI to probe the microstructure of cortical gray matter and its region-specific heterogeneity across cortical areas in the fixed human brain. High angular resolution diffusion imaging (HARDI) data at an isotropic resolution of 92-μm and 30 diffusion-encoding directions were acquired using a 3D diffusion-weighted gradient-and-spin-echo sequence, from prefrontal (Brodmann area 9), primary motor (area 4), primary somatosensory (area 3b), and primary visual (area 17) cortical specimens (n=3 each) from three human subjects. Further, the diffusion MR findings in these cortical areas were compared with histological silver impregnation of the same specimens, in order to investigate the underlying architectonic features that constitute the microstructural basis of diffusion-driven contrasts in cortical gray matter. Our data reveal distinct and region-specific diffusion MR contrasts across the studied areas, allowing delineation of intracortical bands of tangential fibers in specific layers-layer I, layer VI, and the inner and outer bands of Baillarger. The findings of this work demonstrate unique sensitivity of diffusion MRI to differentiate region-specific cortical microstructure in the human brain, and will be useful for myeloarchitectonic mapping of cortical areas as well as to achieve an understanding of the basis of diffusion NMR contrasts in cortical gray matter.
皮质细胞和髓鞘结构的区域性异质性构成了人类大脑皮质区映射的结构基础。在这项研究中，我们研究了扩散 MRI 探测皮质灰质微观结构及其在固定人脑皮质区的特定区域异质性的潜力。使用 3D 扩散加权梯度回波和自旋回波序列，在各向同性分辨率为 92-μm 和 30 个扩散编码方向下，从三个供体的前额皮质（Brodmann 区域 9）、初级运动皮质（区域 4）、初级躯体感觉皮质（区域 3b）和初级视觉皮质（区域 17）标本中获取高角分辨率扩散成像（HARDI）数据（每个区域 3 个标本）。此外，我们还将这些皮质区的扩散 MR 发现与相同标本的组织学银染进行了比较，以研究构成皮质灰质扩散驱动对比微观结构基础的潜在构筑特征。我们的数据揭示了研究区域之间存在明显且特定于区域的扩散 MR 对比，允许在特定层（I 层、VI 层以及 Baillarger 的内带和外带）中描绘出皮质内切线纤维带。这项工作的发现证明了扩散 MRI 具有独特的区分人类大脑特定区域皮质微观结构的敏感性，这对于皮质区的髓鞘构筑映射以及理解皮质灰质中扩散 NMR 对比的基础都将非常有用。
