Superficial white matter fiber systems impede detection of long-range cortical connections in diffusion MR tractography
Superficial white matter fiber systems impede detection of long-range cortical connections in diffusion MR tractography
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DOI：
10.1073/pnas.1418198112
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发表时间：
2015-05-26
影响因子：
11.1
通讯作者：
Ye, Frank Q.
中科院分区：
文献类型：
--
作者：
Reveley, Colin;Seth, Anil K.;Ye, Frank Q.
基于弥散磁共振成像（dMRI）的在体纤维束成像为研究人脑的结构-功能关系打开了新的大门。dMRI最初是为了绘制主要白色物质束的轨迹而开发的，现在越来越多地用于推断皮层的长距离解剖学连接。由于轴突投射起源和终止于灰质，但主要通过深层白色物质，纤维束成像的成功取决于跟踪纤维穿过这一过渡的能力。在这里，我们证明，复杂的安排白色物质纤维居住的皮质片下提出了严峻的挑战，长距离纤维束成像超过大约一半的大脑。我们调查这个问题，通过比较从非常高的分辨率离体猕猴脑标本与相同组织的组织学分析的dMRI。使用纯灰色和白色物质种子的概率跟踪，我们发现，由于致密的白色物质区就在皮质的颗粒下层之下，因此对于长距离扩散跟踪，皮质表面的50%是有效地不可接近的。相应的髓鞘染色切片的分析表明，这些区域共定位与密集和均匀的轴突片运行大多平行于皮质表面，最常见的沟区，但也在许多脑回冠。示踪剂注射到脑沟皮质表明，至少有一些轴突纤维直接通过这些纤维系统。目前和未来的高分辨率dMRI研究人类大脑将需要开发的方法来克服所带来的挑战，表面白色物质系统，以确定长距离的解剖连接准确。
In vivo tractography based on diffusion magnetic resonance imaging (dMRI) has opened new doors to study structure-function relationships in the human brain. Initially developed to map the trajectory of major white matter tracts, dMRI is used increasingly to infer long-range anatomical connections of the cortex. Because axonal projections originate and terminate in the gray matter but travel mainly through the deep white matter, the success of tractography hinges on the capacity to follow fibers across this transition. Here we demonstrate that the complex arrangement of white matter fibers residing just under the cortical sheet poses severe challenges for long-range tractography over roughly half of the brain. We investigate this issue by comparing dMRI from very-high-resolution ex vivo macaque brain specimens with histological analysis of the same tissue. Using probabilistic tracking from pure gray and white matter seeds, we found that similar to 50% of the cortical surface was effectively inaccessible for long-range diffusion tracking because of dense white matter zones just beneath the infragranular layers of the cortex. Analysis of the corresponding myelin-stained sections revealed that these zones colocalized with dense and uniform sheets of axons running mostly parallel to the cortical surface, most often in sulcal regions but also in many gyral crowns. Tracer injection into the sulcal cortex demonstrated that at least some axonal fibers pass directly through these fiber systems. Current and future high-resolution dMRI studies of the human brain will need to develop methods to overcome the challenges posed by superficial white matter systems to determine long-range anatomical connections accurately.