Moreno-Castillo Mayra, Meza Roberto, Romero-Vaca Jesús, Huidobro Nayeli, Méndez-Fernández Abraham, Martínez-Castillo Jaime, Mabil Pedro, Flores Amira, Manjarrez Elias
Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.
Centro de Investigación en Micro y Nanotecnología, Universidad Veracruzana, Veracruz, Mexico.
Front Neurosci. 2020 Jan 31;14:38. doi: 10.3389/fnins.2020.00038. eCollection 2020.
The hemodynamic response is a neurovascular and metabolic process in which there is rapid delivery of blood flow to a neuronal tissue in response to neuronal activation. The functional magnetic resonance imaging (fMRI) and the functional near-infrared spectroscopy (fNIRS), for instance, are based on the physiological principles of such hemodynamic responses. Both techniques allow the mapping of active neuronal regions in which the neurovascular and metabolic events are occurring. However, although both techniques have revolutionized the neurosciences, they are mostly employed for neuroimaging of the human brain but not for the spinal cord during functional tasks. Moreover, little is known about other techniques measuring the hemodynamic response in the spinal cord. The purpose of the present study was to show for the first time that a simple optical system termed direct current photoplethysmography (DC-PPG) can be employed to detect hemodynamic responses of the spinal cord and the brainstem during the functional activation of the spinal central pattern generator (CPG). In particular, we positioned two DC-PPG systems directly on the brainstem and spinal cord during fictive scratching in the cat. The optical DC-PPG systems allowed the trial-by-trial recording of massive hemodynamic signals. We found that the "strength" of the flexor-plus-extensor motoneuron activities during motor episodes of fictive scratching was significantly correlated to the "strengths" of the brainstem and spinal DC-PPG signals. Because the DC-PPG was robustly detected in real-time, we claim that such a functional signal reflects the hemodynamic mass action of the brainstem and spinal cord associated with the CPG motor action. Our findings shed light on an unexplored hemodynamic observable of the spinal CPGs, providing a proof of concept that the DC-PPG can be used for the assessment of the integrity of the human CPGs.
血液动力学反应是一种神经血管和代谢过程，在此过程中，响应神经元激活，会有快速的血流输送至神经元组织。例如，功能磁共振成像（fMRI）和功能近红外光谱（fNIRS）就是基于这种血液动力学反应的生理原理。这两种技术都能绘制出正在发生神经血管和代谢事件的活跃神经元区域。然而，尽管这两种技术都给神经科学带来了变革，但它们大多用于人类大脑的神经成像，而非功能任务期间脊髓的神经成像。此外，对于测量脊髓血液动力学反应的其他技术知之甚少。本研究的目的是首次表明，一种名为直流光电容积描记法（DC-PPG）的简单光学系统可用于检测脊髓中央模式发生器（CPG）功能激活期间脊髓和脑干的血液动力学反应。具体而言，我们在猫进行虚构抓挠时，将两个DC-PPG系统直接置于脑干和脊髓上。光学DC-PPG系统能够逐次试验地记录大量血液动力学信号。我们发现，虚构抓挠运动发作期间屈肌加伸肌运动神经元活动的“强度”与脑干和脊髓DC-PPG信号的“强度”显著相关。由于能实时可靠地检测到DC-PPG，我们认为这种功能信号反映了与CPG运动作用相关的脑干和脊髓的血液动力学整体作用。我们的研究结果揭示了脊髓CPG尚未被探索的血液动力学观测指标，为DC-PPG可用于评估人类CPG完整性提供了概念验证。
