Department of Psychology, Vanderbilt University, Nashville, TN 37203, USA.
Neuroimage. 2013 Jan 1;64:147-55. doi: 10.1016/j.neuroimage.2012.08.060. Epub 2012 Aug 28.
The laminar structure of the cortex has previously been explored both in non-human primates and human subjects using high-resolution functional magnetic resonance imaging (fMRI). However, whether the spatial specificity of the blood-oxygenation-level-dependent (BOLD) fMRI is sufficiently high to reveal lamina specific organization in the cortex reliably is still unclear. In this study we demonstrate for the first time the detection of such layer-specific activation in awake monkeys at the spatial resolution of 200 × 200 × 1000 μm(3) in a vertical 4.7 T scanner. Results collected in trained monkeys are high in contrast-to-noise ratio and low in motion artifacts. Isolation of laminar activation was aided by choosing the optimal slice orientation and thickness using a novel pial vein pattern analysis derived from optical imaging. We found that the percent change of GE-BOLD signal is the highest at a depth corresponding to layer IV. Changes in the middle layers (layer IV) were 30% greater than changes in the top layers (layers I-III), and 32% greater than the bottom layers (layers V/VI). The laminar distribution of BOLD signal correlates well with neural activity reported in the literature. Our results suggest that the high intrinsic spatial resolution of GE-BOLD signal is sufficient for mapping sub-millimeter functional structures in awake monkeys. This degree of spatial specificity will be useful for mapping both laminar activations and columnar structures in the cerebral cortex.
皮层的层状结构以前曾在非人类灵长类动物和人类受试者中使用高分辨率功能磁共振成像（fMRI）进行过研究。然而，血氧水平依赖（BOLD）fMRI 的空间特异性是否足够高，以可靠地揭示皮层中的层特异性组织仍然不清楚。在这项研究中，我们首次在空间分辨率为 200×200×1000μm3 的垂直 4.7T 扫描仪中，在清醒的猴子身上证明了这种层特异性激活的检测。在经过训练的猴子中收集的结果具有高对比噪声比和低运动伪影。通过使用源自光学成像的新型脑表面静脉模式分析来选择最佳的切片方向和厚度，有助于分离层状激活。我们发现，GE-BOLD 信号的百分比变化在对应于第 IV 层的深度处最高。中层（第 IV 层）的变化比顶层（第 I-III 层）的变化大 30%，比底层（第 V/VI 层）的变化大 32%。BOLD 信号的层状分布与文献中报道的神经活动很好地相关。我们的结果表明，GE-BOLD 信号的固有高空间分辨率足以映射清醒猴子的亚毫米级功能结构。这种空间特异性程度将有助于绘制大脑皮层的层状激活和柱状结构。
