Imas Olga A, Ropella Kristina M, Wood James D, Hudetz Anthony G
Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, USA.
Neurosci Lett. 2006 Jul 24;402(3):216-21. doi: 10.1016/j.neulet.2006.04.003. Epub 2006 May 5.
Consciousness presumes a set of integrated functions such as sensory processing, attention, and interpretation, and may depend upon both local and long-range phase synchronization of neuronal activity in cerebral cortex. Here we investigated whether volatile anesthetic isoflurane at concentrations that produce loss of consciousness (LOC) disrupts long-range anterio-posterior and local anterior synchronization of neuronal activity in the rat. In six rats, deep electrodes were chronically implanted in the primary visual cortex (V1) and in two areas of the motor cortex (M1 and M2) for recording of intracortical event-related potentials (ERP). Thirty discrete flashes were presented at random interstimulus intervals of 15-45 s, and ERPs were recorded at stepwise increasing isoflurane concentrations of 0-1.1%. Neuronal synchronization was estimated using wavelet coherence computed from the ERP data band-pass filtered at 5-50 Hz. We found that (1) in the waking state, long-range anterio-posterior coherence in 5-25 Hz and 25-50 Hz frequency bands was significantly higher than local anterior coherence; (2) anterio-posterior coherence in both 5-25 Hz and 26-50 Hz bands was significantly reduced by isoflurane in a concentration-dependent manner; (3) local anterior coherence was not affected by isoflurane at any of the concentrations studied. These findings suggest that a disruption of long-range anterio-posterior rather than local anterior synchronization of neuronal activity precedes the anesthetic-induced loss of consciousness.
意识假定存在一系列整合功能，如感觉处理、注意力和解释，并且可能依赖于大脑皮层中神经元活动的局部和长程相位同步。在这里，我们研究了产生意识丧失（LOC）浓度的挥发性麻醉药异氟烷是否会破坏大鼠神经元活动的长程前后同步和局部前向同步。在六只大鼠中，将深部电极长期植入初级视觉皮层（V1）和运动皮层的两个区域（M1和M2），用于记录皮层内事件相关电位（ERP）。以15 - 45秒的随机刺激间隔呈现30次离散闪光，并在异氟烷浓度逐步增加至0 - 1.1%的情况下记录ERP。使用从小波相干性计算得出的神经元同步性，该小波相干性是根据在5 - 50赫兹带通滤波的ERP数据计算得出的。我们发现：（1）在清醒状态下，5 - 25赫兹和25 - 50赫兹频段的长程前后相干性显著高于局部前向相干性；（2）异氟烷以浓度依赖性方式显著降低了5 - 25赫兹和26 - 50赫兹频段的前后相干性；（3）在所研究的任何浓度下，异氟烷均未影响局部前向相干性。这些发现表明，在麻醉诱导的意识丧失之前，神经元活动的长程前后同步而非局部前向同步受到破坏。
