There is an ongoing debate as to whether ketamine anesthesia suppresses neurophysiologic complexity at doses sufficient for surgical anesthesia, with previous human studies reporting surrogates of both suppressed and preserved levels of cortical complexity. However, these studies have not assessed cortical dynamics in higher gamma frequencies, which have previously been demonstrated to correlate with the level of consciousness during anesthesia. In this study, we used Lempel-Ziv complexity (LZc) to characterize frontal and parietal electroencephalographic complexity (0.5–175 Hz, 0.5–55 Hz, 65–175 Hz) before, during, and after ketamine or propofol anesthesia in the rat. To control for the potential influence of spectral changes in complexity estimation, LZc was normalized with phase-shuffled surrogate data. We demonstrate that ketamine and propofol anesthesia were characterized by a significant reduction in broadband (0.5–175 Hz) LZc. Further analysis showed that while the reduction of LZc during ketamine anesthesia was significant in 65–175 Hz range, during propofol anesthesia, a significant decrease was observed in 0.5–55 Hz bandwidth. LZc in broadband and 0.5–55 Hz range showed a significant increase during emergence from ketamine anesthesia. Phase-shuffled normalized LZc revealed that (1) decrease in complexity during ketamine and propofol anesthesia—not increase in complexity during emergence—were dissociable from the influence of spectral changes, and (2) reduced LZc during ketamine anesthesia was present across all three bandwidths. Ketamine anesthesia was characterized by reduced complexity in high gamma bandwidth, as reflected in both raw and phase-shuffled normalized LZc, which suggests that reduced high gamma complexity is a neurophysiological feature of ketamine anesthesia.

中文翻译：

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氯胺酮和丙泊酚对大鼠脑电图复杂性的状态依赖性和带宽特异性影响

关于氯胺酮麻醉是否在足够手术麻醉的剂量下抑制神经生理复杂性存在持续的争论，先前的人体研究报告了抑制和保留皮质复杂性水平的替代物。然而，这些研究并未评估较高伽马频率下的皮质动力学，此前已证明其与麻醉期间的意识水平相关。在本研究中，我们使用 Lempel-Ziv 复杂性 (LZc) 来表征大鼠在氯胺酮或丙泊酚麻醉之前、期间和之后的额叶和顶叶脑电图复杂性（0.5-175 Hz、0.5-55 Hz、65-175 Hz）。为了控制复杂性估计中频谱变化的潜在影响，LZc 用相位混洗的替代数据进行了归一化。我们证明氯胺酮和丙泊酚麻醉的特点是宽带 (0.5-175 Hz) LZc 显着降低。进一步分析表明，虽然氯胺酮麻醉期间 LZc 在 65-175 Hz 范围内显着降低，但在丙泊酚麻醉期间，在 0.5-55 Hz 带宽内观察到显着降低。在氯胺酮麻醉苏醒期间，宽带和 0.5-55 Hz 范围内的 LZc 显示出显着增加。相位改组归一化 LZc 显示 (1) 氯胺酮和丙泊酚麻醉期间复杂性的降低——而不是苏醒期间复杂性的增加——可从光谱变化的影响中分离出来，并且 (2) 氯胺酮麻醉期间的 LZc 降低存在于所有三个带宽中. 氯胺酮麻醉的特点是降低了高伽马带宽的复杂性，