Nuffield Department of Surgical Sciences and University of Oxford, John Radcliffe Hospital, Oxford, UK.
Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
Br J Anaesth. 2018 Jul;121(1):303-313. doi: 10.1016/j.bja.2018.04.031. Epub 2018 May 25.
Both the cerebral cortex and subcortical structures play important roles in consciousness. Some evidence points to general anaesthesia-induced unconsciousness being associated with distinct patterns of superficial cortical electrophysiological oscillations, but how general anaesthetics influence deep brain neural oscillations and interactions between oscillations in humans is poorly understood.
Local field potentials were recorded in discrete deep brain regions, including anterior cingulate cortex, sensory thalamus, and periaqueductal grey, in humans with implanted deep brain electrodes during induction of unconsciousness with propofol. Power-frequency spectra, phase-amplitude coupling, coherence, and directed functional connectivity analysis were used to characterise local field potentials in the awake and unconscious states.
An increase in alpha (7-13 Hz) power and decrease in gamma (30-90 Hz) power were observed in both deep cortical (ACC, anterior cingulate cortex) and subcortical (sensory thalamus, periaqueductal grey) areas during propofol-induced unconsciousness. Robust alpha-low gamma (30-60 Hz) phase-amplitude coupling induced by general anaesthesia was observed in the anterior cingulate cortex but not in other regions studied. Moreover, alpha oscillations during unconsciousness were highly coherent within the anterior cingulate cortex, and this rhythm exhibited a bidirectional information flow between left and right anterior cingulate cortex but stronger left-to-right flow.
Propofol increases alpha oscillations and attenuates gamma oscillations in both cortical and subcortical areas. The alpha-gamma phase-amplitude coupling and the functional connectivity of alpha oscillations in the anterior cingulate cortex could be specific markers for loss of consciousness.
大脑皮层和皮质下结构在意识中都起着重要作用。一些证据表明，全身麻醉诱导的无意识与皮质表面电生理振荡的明显模式有关，但全身麻醉如何影响深部脑神经振荡以及人类振荡之间的相互作用还知之甚少。
在使用异丙酚诱导无意识期间，在植入深部脑电极的人类中，在离散的深部脑区域（包括前扣带皮层、感觉丘脑和导水管周围灰质）记录局部场电位。使用功率频谱、相位-振幅耦合、相干性和有向功能连接分析来描述清醒和无意识状态下的局部场电位。
在异丙酚诱导的无意识期间，在深部皮质（ACC，前扣带皮层）和皮质下区域（感觉丘脑、导水管周围灰质）都观察到α（7-13 Hz）功率增加和γ（30-90 Hz）功率降低。在全身麻醉诱导下，在前扣带皮层观察到强烈的α-低γ（30-60 Hz）相位-振幅耦合，但在其他研究区域没有观察到。此外，无意识期间的α振荡在前扣带皮层内具有高度相干性，并且该节律在左前扣带皮层和右前扣带皮层之间表现出双向信息流，但左到右的流更强。
异丙酚增加了皮质和皮质下区域的α振荡并减弱了γ振荡。前扣带皮层中的α-γ相位-振幅耦合和α振荡的功能连接可能是意识丧失的特定标志物。
