Harel Noam, Bolan Patrick J, Turner Robert, Ugurbil Kamil, Yacoub Essa
Center for Magnetic Resonance Research, Department of Radiology, School of Medicine, University of Minnesota Minneapolis, MN, USA.
Front Neuroenergetics. 2010 Sep 27;2:130. doi: 10.3389/fnene.2010.00130. eCollection 2010.
The current understanding of fMRI, regarding its vascular origins, is based on numerous assumptions and theoretical modeling, but little experimental validation exists to support or challenge these models. The known functional properties of cerebral vasculature are limited mainly to the large pial surface and the small capillary level vessels. However, a significant lack of knowledge exists regarding the cluster of intermediate-sized vessels, mainly the intracortical, connecting these two groups of vessels and where, arguably, key blood flow regulation takes place. In recent years, advances in MR technology and methodology have enabled the probing of the brain, both structurally and functionally, at resolutions and coverage not previously attainable. Functional MRI has been utilized to map functional units down to the levels of cortical columns and lamina. These capabilities open new possibilities for investigating neurovascular coupling and testing hypotheses regarding fundamental cerebral organization. Here, we summarize recent cutting-edge MR applications for studying neurovascular and functional imaging, both in humans as well as in animal models. In light of the described imaging capabilities, we put forward a theory in which a cortical column, an ensemble of neurons involved in a particular neuronal computation is spatially correlated with a specific vascular unit, i.e., a cluster of an emerging principle vein surrounded by a set of diving arteries. If indeed such a correlation between functional (neuronal) and structural (vascular) units exist as a fundamental intrinsic cortical feature, one could conceivably delineate functional domains in cortical areas that are not known or have not been identified.
目前对于功能磁共振成像（fMRI）血管起源的理解基于众多假设和理论模型，但几乎没有实验验证来支持或质疑这些模型。脑脉管系统已知的功能特性主要局限于大脑软膜表面的大血管和小毛细血管水平的血管。然而，对于连接这两组血管且可能发生关键血流调节的中等大小血管群，尤其是皮质内血管，我们却知之甚少。近年来，磁共振技术和方法的进步使得在以前无法达到的分辨率和覆盖范围下对大脑进行结构和功能探测成为可能。功能磁共振成像已被用于将功能单元映射到皮质柱和板层水平。这些能力为研究神经血管耦合以及检验关于基本脑组织结构的假设开辟了新的可能性。在此，我们总结了近年来用于研究神经血管和功能成像的前沿磁共振应用，包括在人类和动物模型中的应用。鉴于所描述的成像能力，我们提出一种理论，即皮质柱（参与特定神经元计算的一组神经元）在空间上与特定的血管单元相关，即由一组分支动脉包围的一条新兴主静脉的集群。如果功能（神经元）和结构（血管）单元之间确实存在这种相关性，作为一种基本的内在皮质特征，那么就可以想象地描绘出皮质区域中未知或尚未确定的功能域。
