Devor Anna, Ulbert Istvan, Dunn Andrew K, Narayanan Suresh N, Jones Stephanie R, Andermann Mark L, Boas David A, Dale Anders M
Massachusetts General Hospital NMR Center and Program in Biophysics, Harvard Medical School, Charlestown, MA 02129, USA.
Proc Natl Acad Sci U S A. 2005 Mar 8;102(10):3822-7. doi: 10.1073/pnas.0407789102. Epub 2005 Feb 25.
Accurate interpretation of functional MRI (fMRI) signals requires knowledge of the relationship between the hemodynamic response and the neuronal activity that underlies it. Here we address the question of coupling between pre- and postsynaptic neuronal activity and the hemodynamic response in rodent somatosensory (Barrel) cortex in response to single-whisker deflection. Using full-field multiwavelength optical imaging of hemoglobin oxygenation and electrophysiological recordings of spiking activity and local field potentials, we demonstrate that a point hemodynamic measure is influenced by neuronal activity across multiple cortical columns. We demonstrate that the hemodynamic response is a spatiotemporal convolution of the neuronal activation. Therefore, positive hemodynamic response in one cortical column might be explained by neuronal activity not only in that column but also in the neighboring columns. Thus, attempts at characterizing the neurovascular relationship based on point measurements of electrophysiology and hemodynamics may yield inconsistent results, depending on the spatial extent of neuronal activation. The finding that the hemodynamic signal observed at a given location is a function of electrophysiological activity over a broad spatial region helps explain a previously observed increase of local vascular response beyond the saturation of local neuronal activity. We also demonstrate that the oxy- and total-hemoglobin hemodynamic responses can be well approximated by space-time separable functions with an antagonistic center-surround spatial pattern extending over several millimeters. The surround "negative" hemodynamic activity did not correspond to observable changes in neuronal activity. The complex spatial integration of the hemodynamic response should be considered when interpreting fMRI data.
功能磁共振成像（fMRI）信号的准确解读需要了解血流动力学反应与作为其基础的神经元活动之间的关系。在此，我们探讨了啮齿动物体感（桶状）皮层中突触前和突触后神经元活动与血流动力学反应之间的耦合问题，该反应是对单根触须偏转的响应。通过对血红蛋白氧合进行全场多波长光学成像以及对尖峰活动和局部场电位进行电生理记录，我们证明点血流动力学测量受到多个皮质柱中神经元活动的影响。我们证明血流动力学反应是神经元激活的时空卷积。因此，一个皮质柱中的正向血流动力学反应不仅可以由该柱中的神经元活动解释，也可以由相邻柱中的神经元活动解释。因此，基于电生理学和血流动力学的点测量来表征神经血管关系的尝试可能会产生不一致的结果，这取决于神经元激活的空间范围。在给定位置观察到的血流动力学信号是广泛空间区域内电生理活动的函数这一发现，有助于解释先前观察到的局部血管反应在局部神经元活动饱和后仍增加的现象。我们还证明，氧合血红蛋白和总血红蛋白的血流动力学反应可以通过时空可分离函数很好地近似，该函数具有延伸数毫米的拮抗中心 - 周边空间模式。周边的“负”血流动力学活动与可观察到的神经元活动变化不对应。在解释fMRI数据时应考虑血流动力学反应的复杂空间整合。
