Modelling the depth-dependent VASO and BOLD responses in human primary visual cortex.
Modelling the depth-dependent VASO and BOLD responses in human primary visual cortex.
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DOI：
10.1002/hbm.26094
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发表时间：
2023-02-01
影响因子：
4.8
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中科院分区：
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使用血氧水平依赖性（BOLD）对比的功能磁共振成像（fMRI）是无创研究人脑功能的常用方法。梯度回波 (GRE) BOLD 对血管中的血氧变化高度敏感；然而，在深度相关（也称为层流或层特异性）功能磁共振成像中，由于信号从激活的较低层泄漏到浅层，空间信号特异性可能会降低。另外，与 BOLD 相比，使用血管空间占用 (VASO) 对比的生理变量（例如脑血量）显示出更高的空间特异性。为了更好地理解血容量和氧合变化等生理机制，并解释测量的深度依赖性响应，需要反映该尺度血管特性的模型。为此，我们扩展并修改了之前开发的“皮质血管模型”，用于预测人类初级视觉皮层中特定层的 BOLD 信号变化，以预测特定层的 VASO 反应。为了评估该模型，我们将预测结果与一组健康参与者同时进行 VASO 和 BOLD 测量的实验结果进行了比较。将模型与我们的实验数据进行拟合，可以估计神经活动时不同血管区室的 CBV 变化。我们发现刺激诱发的 CBV 变化主要发生在小动脉、毛细血管和皮质内动脉，小静脉和 ICV 的贡献较小。我们的结果证实，与 BOLD 相比，VASO 不太容易受到大血管效应的影响，因为皮质内动脉的血容量变化并没有显着影响所得的深度依赖性 VASO 曲线，而深度依赖性 BOLD 曲线显示出对皮质内静脉信号贡献的偏差。在这项研究中，我们测量了人类初级视觉皮层中深度依赖性血氧水平依赖性和血管空间占用曲线，然后使用简单的皮质血管模型模拟这些反应，以获得不同血管区室对神经活动的 CBV 变化的估计。
Functional magnetic resonance imaging (fMRI) using a blood‐oxygenation‐level‐dependent (BOLD) contrast is a common method for studying human brain function noninvasively. Gradient‐echo (GRE) BOLD is highly sensitive to the blood oxygenation change in blood vessels; however, the spatial signal specificity can be degraded due to signal leakage from activated lower layers to superficial layers in depth‐dependent (also called laminar or layer‐specific) fMRI. Alternatively, physiological variables such as cerebral blood volume using the VAscular‐Space‐Occupancy (VASO) contrast have shown higher spatial specificity compared to BOLD. To better understand the physiological mechanisms such as blood volume and oxygenation changes and to interpret the measured depth‐dependent responses, models are needed which reflect vascular properties at this scale. For this purpose, we extended and modified the “cortical vascular model” previously developed to predict layer‐specific BOLD signal changes in human primary visual cortex to also predict a layer‐specific VASO response. To evaluate the model, we compared the predictions with experimental results of simultaneous VASO and BOLD measurements in a group of healthy participants. Fitting the model to our experimental data provided an estimate of CBV change in different vascular compartments upon neural activity. We found that stimulus‐evoked CBV change mainly occurs in small arterioles, capillaries, and intracortical arteries and that the contribution from venules and ICVs is smaller. Our results confirm that VASO is less susceptible to large vessel effects compared to BOLD, as blood volume changes in intracortical arteries did not substantially affect the resulting depth‐dependent VASO profiles, whereas depth‐dependent BOLD profiles showed a bias towards signal contributions from intracortical veins. In this study, we have measured the depth‐dependent blood‐oxygenation‐level‐dependent and VAscular‐Space‐Occupancy profiles in the human primary visual cortex and then simulated these responses using a simple cortical vascular model to obtain an estimate of CBV change in different vascular compartments upon neural activity.
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