National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
Neuroimage. 2012 Jan 16;59(2):1451-60. doi: 10.1016/j.neuroimage.2011.08.001. Epub 2011 Aug 7.
The spatiotemporal characteristics of the hemodynamic response to increased neural activity were investigated at the level of individual intracortical vessels using BOLD-fMRI in a well-established rodent model of somatosensory stimulation at 11.7 T. Functional maps of the rat barrel cortex were obtained at 150 × 150 × 500 μm spatial resolution every 200 ms. The high spatial resolution allowed separation of active voxels into those containing intracortical macro vessels, mainly vein/venules (referred to as macrovasculature), and those enriched with arteries/capillaries and small venules (referred to as microvasculature) since the macro vessel can be readily mapped due to the fast T2 decay of blood at 11.7 T. The earliest BOLD response was observed within layers IV-V by 0.8s following stimulation and encompassed mainly the voxels containing the microvasculature and some confined macrovasculature voxels. By 1.2s, the BOLD signal propagated to the macrovasculature voxels where the peak BOLD signal was 2-3 times higher than that of the microvasculature voxels. The BOLD response propagated in individual venules/veins far from neuronal sources at later times. This was also observed in layers IV-V of the barrel cortex after specific stimulation of separated whisker rows. These results directly visualized that the earliest hemodynamic changes to increased neural activity occur mainly in the microvasculature and spread toward the macrovasculature. However, at peak response, the BOLD signal is dominated by penetrating venules even at layers IV-V of the cortex.
使用 11.7T 下的 BOLD-fMRI 在成熟的感觉刺激啮齿动物模型中研究了神经活动增加时血液动力学反应的时空特征在单个皮质内血管水平。以 150×150×500μm 的空间分辨率每 200ms 获得大鼠皮层桶状核功能图。高空间分辨率允许将活跃体素分为包含皮质内大血管的体素,主要是静脉/小静脉(称为大血管)和富含动脉/毛细血管和小静脉的体素(称为微血管),因为大血管可以由于 11.7T 下血液的快速 T2 衰减而易于绘制。刺激后 0.8s 内,最早的 BOLD 反应在 IV-V 层观察到,主要包含包含微血管和一些局限于大血管的体素。在 1.2s 时,BOLD 信号传播到大血管体素,其中 BOLD 信号峰值比微血管体素高 2-3 倍。BOLD 反应在远离神经元源的单个静脉/血管中在后期传播。在分离的胡须行特异性刺激后,在桶状皮层的 IV-V 层也观察到了这种情况。这些结果直接显示,增加神经活动引起的最早血液动力学变化主要发生在微血管中,并向大血管传播。然而,在峰值反应时,BOLD 信号甚至在皮层的 IV-V 层也主要由穿透性静脉主导。