Investigating the spatiotemporal characteristics of the deoxyhemoglobin-related and deoxyhemoglobin-unrelated functional hemodynamic response across cortical layers in awake marmosets.
Investigating the spatiotemporal characteristics of the deoxyhemoglobin-related and deoxyhemoglobin-unrelated functional hemodynamic response across cortical layers in awake marmosets.
复制标题
研究清醒狨猴皮质层中与脱氧血红蛋白相关和与脱氧血红蛋白无关的功能性血流动力学反应的时空特征。
DOI：
10.1016/j.neuroimage.2017.03.005
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发表时间：
2018
期刊：
影响因子：
5.7
通讯作者：
Silva,AfonsoC
中科院分区：
文献类型：
--
作者：
Yen,CecilChern-Chyi;Papoti,Daniel;Silva,AfonsoC
血氧水平依赖（BOLD）功能磁共振成像（fMRI）已成为一个主要的工具来映射神经活动。然而，时空特性的BOLD功能性血流动力学反应的皮质层仍然知之甚少。虽然人类功能磁共振成像研究的时空分辨率低，在动物模型中使用麻醉引入了混杂因素。此外，当使用短重复时间（TR）时，流入对fMRI信号的贡献变得不可忽略。在目前的工作中，我们绘制了清醒的绒猴BOLD功能磁共振成像反应的体感刺激。为了解决上述技术问题，我们使用了双回波梯度回波平面成像（GR-EPI）序列来分离脱氧血红蛋白相关反应（绝对T2* 差异）和脱氧血红蛋白无关反应（相对S 0变化）。我们采用空间饱和脉冲来饱和传入动脉自旋并减少流入效应。功能性GR-EPI图像从具有两种不同回波时间（13.5和40.5 ms）和TR=0.2 s的单个冠状切片获得。计算BOLD、T2* 和S 0图像，并在初级躯体感觉皮层的两个半球检测它们的功能反应，由此衍生出五个层区（L1+2、L3、L4、L5和L 6）。的时空分布的BOLD反应在皮层层是异质的，与中间层具有最高的BOLD振幅和最短的发病时间。ΔT2* 也显示出类似的趋势。然而，仅在L1+2中检测到功能性S 0变化，且起效时间快。由于流入效应被最小化，L1+2的S 0功能变化的来源可能是由于脑血容量的功能性增加和静脉外和静脉内室中未建模的T2* 变化引起的脑脊液体积分数降低。当解释浅层的层状BOLD功能磁共振成像变化作为潜在神经活动的替代时，应谨慎行事。
Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) has become a major tool to map neural activity. However, the spatiotemporal characteristics of the BOLD functional hemodynamic response across the cortical layers remain poorly understood. While human fMRI studies suffer from low spatiotemporal resolution, the use of anesthesia in animal models introduces confounding factors. Additionally, inflow contributions to the fMRI signal become non-negligible when short repetition times (TRs) are used. In the present work, we mapped the BOLD fMRI response to somatosensory stimulation in awake marmosets. To address the above technical concerns, we used a dual-echo gradient-recalled echo planar imaging (GR-EPI) sequence to separate the deoxyhemoglobin-related response (absolute T2* differences) from the deoxyhemoglobin-unrelated response (relative S0changes). We employed a spatial saturation pulse to saturate incoming arterial spins and reduce inflow effects. Functional GR-EPI images were obtained from a single coronal slice with two different echo times (13.5 and 40.5 ms) and TR=0.2 s. BOLD, T2*, and S0images were calculated and their functional responses were detected in both hemispheres of primary somatosensory cortex, from which five laminar regions (L1+2, L3, L4, L5, and L6) were derived. The spatiotemporal distribution of the BOLD response across the cortical layers was heterogeneous, with the middle layers having the highest BOLD amplitudes and shortest onset times. ΔT2* also showed a similar trend. However, functional S0changes were detected only in L1+2, with a fast onset time. Because inflow effects were minimized, the source of S0functional changes in L1+2 could be attributed to a reduction of cerebrospinal fluid volume fraction due to the functional increase in cerebral blood volume and to unmodeled T2* changes in the extra- and intra-venous compartments. Caution should be exercised when interpreting laminar BOLD fMRI changes in superficial layers as surrogates of underlying neural activity.