Weber Bruno, Keller Anna Lena, Reichold Johannes, Logothetis Nikos K
Max-Planck Institut für biologische Kybernetik, Spemannstr. 38, 72076 Tübingen, Germany.
Cereb Cortex. 2008 Oct;18(10):2318-30. doi: 10.1093/cercor/bhm259. Epub 2008 Jan 24.
In functional neuroimaging, neurovascular coupling is used to generate maps of hemodynamic changes that are assumed to be surrogates of regional neural activation. The aim of this study was to characterize the microvascular system of the primate cortex as a basis for understanding the constraints imposed on a region's hemodynamic response by the vascular architecture, density, as well as area- and layer-specific variations. In the macaque visual cortex, an array of anatomical techniques has been applied, including corrosion casts, immunohistochemistry, and cytochrome oxidase (COX) staining. Detailed measurements of regional vascular length density, volume fraction, and surface density revealed a similar vascularization in different visual areas. Whereas the lower cortical layers showed a positive correlation between the vascular and cell density, this relationship was very weak in the upper layers. Synapse density values taken from the literature also displayed a very moderate correlation with the vascular density. However, the vascular density was strongly correlated with the steady-state metabolic demand as measured by COX activity. This observation suggests that although the number of neurons and synapses determines an upper bound on an area's integrative capacity, its vascularization reflects the neural activity of those subpopulations that represent a "default" mode of brain steady state.
在功能神经成像中，神经血管耦合用于生成血流动力学变化图谱，这些变化被认为是区域神经激活的替代指标。本研究的目的是表征灵长类动物皮层的微血管系统，以此作为理解血管结构、密度以及区域和层特异性变化对区域血流动力学反应施加的限制的基础。在猕猴视觉皮层中，已经应用了一系列解剖学技术，包括腐蚀铸型、免疫组织化学和细胞色素氧化酶（COX）染色。对区域血管长度密度、体积分数和表面密度的详细测量显示，不同视觉区域的血管化情况相似。虽然皮层下层的血管密度与细胞密度呈正相关，但在上层这种关系非常弱。从文献中获取的突触密度值与血管密度也仅呈现出非常适度的相关性。然而，血管密度与通过COX活性测量的稳态代谢需求密切相关。这一观察结果表明，虽然神经元和突触的数量决定了一个区域整合能力的上限，但其血管化反映了那些代表大脑稳态“默认”模式的亚群的神经活动。
