Little Graham, Poirier Charles, Bore Arnaud, Parent Martin, Petit Laurent, Descoteaux Maxime
Department of Computer Science, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
CERVO Brain Research Center and Department of Psychiatry and Neuroscience, Faculty of Medicine, Université Laval, Quebec City, Quebec, Canada.
Hum Brain Mapp. 2025 Jun 1;46(8):e70245. doi: 10.1002/hbm.70245.
In primates, the putamen and the caudate nucleus are connected by ~1 mm-thick caudolenticular gray matter bridges (CLGBs) interspersed between the white matter bundles of the internal capsule. Little is understood about the functional or microstructural properties of the CLGBs. In studies proposing high resolution diffusion magnetic resonance imaging (dMRI) techniques, CLGBs have been qualitatively identified as an example of superior imaging quality; however, the microstructural properties of these structures have yet to be examined. In this study, it is demonstrated for the first time that dMRI is sensitive to an organized anisotropic signal oriented in the direction parallel to the CLGBs, suggesting that dMRI could be a useful imaging method for probing the microstructure of the CLGBs. To demonstrate the anisotropic diffusion signal is coherently organized along the extent of the CLGBs and to enable a subsequent CLGB microstructural measurement, a customized tractography seeding and filtering method is proposed that utilizes the shape of the human striatum (putamen + caudate nucleus) to reconstruct the CLGBs in 3D. The proposed seeding strategy seeds tractography streamlines outward and normal to the surface of a 3D model of the striatum such that reconstructed streamlines are more likely to follow the diffusion signal peaks aligned parallel to the CLGBs. The method is applied to three different diffusion datasets, namely a high resolution 760 μm isotropic diffusion dataset acquired on a single subject, the test-retest cohort included as part of the human connectome project (N = 44) with diffusion data acquired at 1.25 mm isotropic, and a locally acquired "clinical" test-retest dataset acquired at 2.0 mm isotropic (N = 24). Reconstructed CLGBs directly overlap expected gray matter regions in the human brain for all three datasets. In addition, the method is shown to accurately reconstruct CLGBs repeatedly across multiple test-retest cohorts. The tractography CLGB reconstructions are then used to extract a quantitative measurement of microstructure from a local model of the diffusion signal along the CLGBs themselves. This is the first work to comprehensively study the CLGBs in vivo using dMRI and presents techniques suitable for future human neuroscience studies targeting these structures.
在灵长类动物中，壳核和尾状核由约1毫米厚的尾壳灰质桥（CLGBs）相连，这些灰质桥散布在内囊的白质束之间。人们对CLGBs的功能或微观结构特性了解甚少。在提出高分辨率扩散磁共振成像（dMRI）技术的研究中，CLGBs已被定性地确定为成像质量优越的一个例子；然而，这些结构的微观结构特性尚未得到研究。在本研究中，首次证明dMRI对沿CLGBs平行方向排列的有组织的各向异性信号敏感，这表明dMRI可能是探测CLGBs微观结构的一种有用的成像方法。为了证明各向异性扩散信号沿CLGBs的范围连贯地组织起来，并能够进行后续的CLGB微观结构测量，提出了一种定制的纤维束成像种子点和滤波方法，该方法利用人类纹状体（壳核 + 尾状核）的形状在三维空间中重建CLGBs。所提出的种子点策略使纤维束成像流线向外并垂直于纹状体三维模型的表面，这样重建的流线更有可能沿着与CLGBs平行排列的扩散信号峰值延伸。该方法应用于三个不同的扩散数据集，即对一名受试者采集的高分辨率760μm各向同性扩散数据集、作为人类连接组计划一部分的重测队列（N = 44），其扩散数据采集的各向同性为1.25mm，以及本地采集的各向同性为2.0mm的“临床”重测数据集（N = 24）。对于所有这三个数据集，重建的CLGBs直接与人类大脑中预期的灰质区域重叠。此外，该方法被证明能够在多个重测队列中反复准确地重建CLGBs。然后，利用纤维束成像CLGB重建结果从沿CLGBs本身的扩散信号局部模型中提取微观结构的定量测量值。这是第一项使用dMRI在体内全面研究CLGBs的工作，并提出了适用于未来针对这些结构的人类神经科学研究的技术。
