Laminar specificity in monkey V1 using high-resolution SE-fMRI
Laminar specificity in monkey V1 using high-resolution SE-fMRI
复制标题
DOI：
10.1016/j.mri.2005.12.032
复制
发表时间：
2006-05-01
影响因子：
2.5
通讯作者：
Logothetis, NK
中科院分区：
文献类型：
--
作者：
Goense, JBM;Logothetis, NK
哺乳动物新皮质的分层被广泛用作描述广泛的解剖学和生理学数据的参考。它的价值在于观察到在所有被检查的物种中，皮质传入神经、内在细胞和投射神经元都根据层进行自我组织。对新皮质微电路进行的计算的理解主要依赖于对层间连接模式和体内层内生理过程的研究。高分辨率功能神经成像能够使单个皮质层或柱的活动可视化，可能会对此类研究做出巨大贡献。然而，用常用的 GE-EPI 测量的 BOLD 效应包含宏观静脉血管和毛细血管的贡献。皮质静脉的低密度限制了功能磁共振成像信号的有效空间特异性，并产生了针对大血管系统加权的地图，因此可能与神经元活动增加的实际部位显着不同。产生明显 T-2 加权 BOLD 图像的自旋回波 (SE) 序列已被证明可以通过提高信号对实质自旋的敏感性来提高空间特异性，特别是在高磁场下。在这里，我们使用 4.7 T 的 SE-fMRI 来检查通过刺激猴子初级视觉皮层获得的功能图的特异性和分辨率。皮质层可以清晰可见，功能活动主要位于皮质 IV 层/Duvemoy 3 层。序列参数的选择会影响 fMRI 信号，因为 SE-EPI 除了 T-2 依赖性之外，本质上对 T-2* 敏感。使用限制 T2* 效应的参数可以产生更高的特异性和更好的皮质层可视化。由于使用 SE 对高空间分辨率的要求严重降低了时间分辨率，因此我们使用了一种刺激协议，允许以更高的有效时间分辨率进行采样。通过这种方式，可以获得高空间和高时间分辨率的 SE-fMRI 数据。 (c) 2006 Elsevier Inc. 保留所有权利。
The lamination of mammalian neocortex is widely used as reference for describing a wide range of anatomical and physiological data. Its value ties in the observation that in all examined species, cortical afferents, intrinsic cells and projection neurons organize themselves with respect to the laminae. The comprehension of the computations, carried out by the neocortical microcircuits, critically relies on the study of the interlaminar connectivity patterns and the intralaminar physiological processes in vivo. High-resolution functional neuroimaging, enabling the visualization of activity in individual cortical laminae or columns, may greatly contribute in such studies. Yet, the BOLD effect, as measured with the commonly used GE-EPI, contains contributions from both macroscopic venous blood vessels and capillaries. The low density of the cortical veins limits the effective spatial specificity of the fMRI signal and yields maps that are weighted toward the macrovasculature, which thus can be significantly different from the actual site of increased neuronal activity. Spin-echo (SE) sequences yielding apparent T-2-weighted BOLD images have been shown to improve spatial specificity by increasing the sensitivity of the signal to spins of the parenchyma, particularly at high magnetic fields. Here we used SE-fMRI at 4.7 T to examine the specificity and resolution of functional maps obtained by stimulating the primary visual cortex of monkeys. Cortical layers could be clearly visualized, and functional activity was predominantly localized in cortical layer IV/Duvemoy layer 3. The choice of sequence parameters influences the fMRI signal, as the SE-EPI is by nature sensitive to T-2* in addition to its T-2 dependency. Using parameters that limit T2* effects yielded higher specificity and better visualization of the cortical laminae. Because the demands of high-spatial resolution using SE severely decreases temporal resolution, we used a stimulus protocol that allows sampling at higher effective temporal resolution. This way, it was possible to acquire high-spatial and high-temporal resolution SE-fMRI data. (c) 2006 Elsevier Inc. All rights reserved.