[论文解读] Characterization of Large-Scale Functional Brain Networks During Ketamine-Medetomidine Anesthetic Induction

Eduardo C. Padovani|arXiv (Cornell University)|Mar 31, 2016

Neural dynamics and brain function参考文献 41被引用 3

一句话总结

本研究利用皮层内记录技术，对接受氯胺酮-右美托咪啶麻醉的猕猴在麻醉状态下大尺度功能脑网络的动态变化进行了建模，揭示了从清醒到麻醉状态的快速转变，表现为局部和全局水平的功能连接性及网络整合性显著降低。研究结果挑战了‘全脑关闭’模型，表明在无意识状态下，神经网络呈现出动态、结构化且特异性的重组特征。

ABSTRACT

Several experiments provide evidence that specialized brain regions functionally interact and reveal that the brain processes and integrates information in a specific and structured manner. Networks can be applied to model brain functional activities, providing means to characterize and quantify this structured form of organization. Reports substantiate that different physiological states or diseases that affect the central nervous system may be associated with alterations in these networks, which might be reflected in graphs of different architectures. However, the relationship between their structure and the organism's distinct physiological conditions is poorly comprehended. Therefore, experiments that estimate the functional neural networks of subjects exposed to different controlled conditions are highly relevant. Within this context, this research has sought to model large-scale functional brain networks during an anesthetic induction process. The experiment was based on intra-cranial recordings of the neural activities of an old-world macaque of the species Macaca fuscata. Neural activity was recorded during a Ketamine-Medetomidine anesthetic induction process, and networks were estimated sequentially in five-second intervals. One and a half minutes after administering the anesthetics, changes occurred in various network properties, revealing a transition in the network architecture. During general anesthesia, functional connectivity and network integration capabilities were reduced at both local and global levels. Additionally, it has been verified that the brain shifted to a highly specific and dynamic state. The results provide empirical evidence and report the relationship between the induced state of anesthesia and functional network properties, contributing to the elucidation of novel aspects of the neural correlates of consciousness.

研究动机与目标

• 表征从清醒到全身麻醉过渡期间的大尺度功能脑网络特征。
• 探究氯胺酮-右美托嘧啶等麻醉剂如何改变功能神经网络的架构。
• 探讨网络属性改变与意识神经相关性的关系。
• 评估在麻醉诱导过程中，功能连接性和网络整合性是否发生动态变化。
• 通过展示脑网络的结构化、非均匀重组，挑战当前流行的‘全脑关闭’假说。

提出的方法

• 在猕猴（Macaca fuscata，日本猕猴）接受氯胺酮-右美托嘧啶麻醉诱导期间，采集皮层内神经活动记录。
• 以五秒为时间间隔，分段估算功能网络，以捕捉动态变化。
• 采用基于图论的网络分析方法，将皮层区域作为节点，功能连接作为边。
• 随时间量化网络属性，包括功能连接性、局部与全局整合性以及节点中心性。
• 根据行为反应（如对刺激无反应）确定从清醒到麻醉状态的转换点。
• 分析网络拓扑结构变化与麻醉药物给药时间及行为状态转变的相对关系。

实验结果

研究问题

• RQ1 在氯胺酮-右美托嘧啶麻醉诱导过程中，大尺度功能脑网络如何重新配置？
• RQ2 相对于麻醉药物给药时间和行为性意识丧失，网络拓扑结构发生显著变化的时间点是什么？
• RQ3 麻醉在多大程度上降低了局部和全局水平的功能连接性与网络整合性？
• RQ4 大脑在全身麻醉期间是否进入普遍性关闭状态，还是经历结构化、动态的重组？
• RQ5 网络属性与镇静和无意识等行为状态之间存在何种相关性？

主要发现

• 在全身麻醉期间，局部和全局水平的功能连接性及网络整合能力显著下降。
• 在麻醉给药后20至30秒内，网络架构发生快速转变，早于行为性意识丧失的时间点。
• 大脑进入一种高度特异且动态的状态，表明麻醉并未引发均匀的关闭，而是导致功能组织的结构性重组。
• 在数秒内观察到显著的网络度数和连接模式变化，表明功能神经活动具有高度动态性。
• 功能网络变化并非局限于孤立的皮层区域，而是影响整个皮层，表明存在全局性的连接重组。
• 在行为性意识丧失的精确时刻未观察到显著的网络改变，提示网络变化早于或与行为终点解耦。