Department of Anesthesiology, University of MichiganAnn Arbor, MI, United States.
Center of Consciousness Science, University of MichiganAnn Arbor, MI, United States.
Front Neural Circuits. 2017 Jun 20;11:44. doi: 10.3389/fncir.2017.00044. eCollection 2017.
There has been controversy regarding the precise mechanisms of anesthetic-induced unconsciousness, with two salient approaches that have emerged within systems neuroscience. One prominent approach is the "bottom up" paradigm, which argues that anesthetics suppress consciousness by modulating sleep-wake nuclei and neural circuits in the brainstem and diencephalon that have evolved to control arousal states. Another approach is the "top-down" paradigm, which argues that anesthetics suppress consciousness by modulating the cortical and thalamocortical circuits involved in the integration of neural information. In this article, we synthesize these approaches by mapping bottom-up and top-down mechanisms of general anesthetics to two distinct but inter-related dimensions of consciousness: level and content. We show how this explains certain empirical observations regarding the diversity of anesthetic drug effects. We conclude with a more nuanced discussion of how levels and contents of consciousness interact to generate subjective experience and what this implies for the mechanisms of anesthetic-induced unconsciousness.
关于麻醉诱导意识丧失的确切机制一直存在争议，系统神经科学中出现了两种突出的方法。一种主要的方法是“自下而上”的范式，它认为麻醉剂通过调节脑干和间脑中的睡眠-觉醒核和神经网络来抑制意识，这些核和神经网络是为了控制觉醒状态而进化的。另一种方法是“自上而下”的范式，它认为麻醉剂通过调节涉及整合神经信息的皮质和丘脑皮质回路来抑制意识。在本文中，我们通过将全身麻醉的自下而上和自上而下的机制映射到意识的两个不同但相互关联的维度：水平和内容，来综合这些方法。我们展示了这如何解释关于麻醉药物效应多样性的某些经验观察。最后，我们更细致地讨论了意识的水平和内容如何相互作用产生主观体验，以及这对麻醉诱导无意识的机制意味着什么。
