BACKGROUND Neurophysiologic complexity in the cortex has been shown to reflect changes in the level of consciousness in adults but remains incompletely understood in the developing brain. This study aimed to address changes in cortical complexity related to age and anesthetic state transitions. This study tested the hypotheses that cortical complexity would (1) increase with developmental age and (2) decrease during general anesthesia. METHODS This was a single-center, prospective, cross-sectional study of healthy (American Society of Anesthesiologists physical status I or II) children (n = 50) of age 8 to 16 undergoing surgery with general anesthesia at Michigan Medicine. This age range was chosen because it reflects a period of substantial brain network maturation. Whole scalp (16-channel), wireless electroencephalographic data were collected from the preoperative period through the recovery of consciousness. Cortical complexity was measured using the Lempel-Ziv algorithm and analyzed during the baseline, premedication, maintenance of general anesthesia, and clinical recovery periods. The effect of spectral power on Lempel-Ziv complexity was analyzed by comparing the original complexity value with those of surrogate time series generated through phase randomization that preserves power spectrum. RESULTS Baseline spatiotemporal Lempel-Ziv complexity increased with age (yr; slope [95% CI], 0.010 [0.004, 0.016]; P < 0.001); when normalized to account for spectral power, there was no significant age effect on cortical complexity (0.001 [-0.004, 0.005]; P = 0.737). General anesthesia was associated with a significant decrease in spatiotemporal complexity (median [25th, 75th]; baseline, 0.660 [0.620, 0.690] vs. maintenance, 0.459 [0.402, 0.527]; P < 0.001), and spatiotemporal complexity exceeded baseline levels during postoperative recovery (0.704 [0.642, 0.745]; P = 0.009). When normalized, there was a similar reduction in complexity during general anesthesia (baseline, 0.913 [0.887, 0.923] vs. maintenance 0.851 [0.823, 0.877]; P < 0.001), but complexity remained significantly reduced during recovery (0.873 [0.840, 0.902], P < 0.001). CONCLUSIONS Cortical complexity increased with developmental age and decreased during general anesthesia. This association remained significant when controlling for spectral changes during anesthetic-induced perturbations in consciousness but not with developmental age. EDITOR’S PERSPECTIVE

中文翻译：

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儿童的神经生理复杂性随着发育年龄的增长而增加，并因全身麻醉而降低。

背景 皮质中的神经生理复杂性已被证明反映了成人意识水平的变化，但在发育中的大脑中仍未完全了解。本研究旨在解决与年龄和麻醉状态转变相关的皮质复杂性变化。该研究测试了以下假设：皮质复杂性将 (1) 随着发育年龄增加和 (2) 在全身麻醉期间减少。方法 这是一项单中心、前瞻性、横断面研究，对象为在密歇根医学院接受全身麻醉手术的 8 至 16 岁健康（美国麻醉医师协会身体状况 I 或 II）儿童（n = 50）。选择这个年龄范围是因为它反映了大脑网络大量成熟的时期。全头皮（16通道），从术前到意识恢复期间收集无线脑电图数据。使用 Lempel-Ziv 算法测量皮质复杂性，并在基线、术前用药、全身麻醉维持和临床恢复期间进行分析。通过将原始复杂度值与通过保留功率谱的相位随机化生成的替代时间序列的复杂度值进行比较，分析了谱功率对 Lempel-Ziv 复杂度的影响。结果 基线时空 Lempel-Ziv 复杂性随年龄增加（年；斜率 [95% CI]，0.010 [0.004, 0.016]；P < 0.001）；当归一化以解释光谱功率时，对皮质复杂性没有显着的年龄影响（0.001 [-0.004, 0.005]; P = 0.737）。全身麻醉与时空复杂性显着降低相关（中位数 [25th, 75th]；基线，0.660 [0.620, 0.690] vs.维持，0.459 [0.402, 0.527]；P < 0.001），并且时空复杂性超过基线水平术后恢复（0.704 [0.642, 0.745]；P = 0.009）。归一化后，全身麻醉期间的复杂性也有类似的降低（基线，0.913 [0.887, 0.923] vs. 维持 0.851 [0.823, 0.877]；P < 0.001），但在恢复期间复杂性仍然显着降低（0.873 [0.840, 0.902]） ]，P < 0.001）。结论皮质复杂性随着发育年龄的增长而增加，并在全身麻醉期间降低。在控制麻醉引起的意识扰动期间的光谱变化时，这种关联仍然很重要，但与发育年龄无关。编辑的观点