Consciousness is thought to scale with brain complexity, and it may be diminished in anesthesia. Lempel-Ziv complexity (LZC) of field potentials has been shown to be a promising measure of the level of consciousness in anesthetized human subjects, neurological patients, and across the sleep-wake states in rats. Whether this relationship holds for intrinsic networks obtained by functional brain imaging has not been tested. To fill this gap of knowledge, we estimated LZC from large-scale dynamic analysis of functional magnetic resonance images (fMRI) in conscious sedated and unconscious anesthetized rats. Blood oxygen dependent (BOLD) signals were obtained from 30-min whole-brain resting-state scans while the anesthetic propofol was infused intravenously at constant infusion rates of 20 mg/kg/h (conscious sedated) and 40 mg/kg/h (unconscious). Dynamic brain networks were defined at voxel level by sliding window analysis of regional homogeneity (ReHo) of the BOLD signal. From scans performed at low to high propofol dose, the LZC was significantly reduced by 110%. The results suggest that the difference in LZC between conscious sedated and anesthetized unconscious subjects is conserved in rats and this effect is detectable in large-scale brain network obtained from fMRI.
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机译：人们认为意识与大脑的复杂性成正比，在麻醉中可能会减弱。场势的Lempel-Ziv复杂度（LZC）已被证明是麻醉的人类受试者，神经病患者以及大鼠整个睡眠-觉醒状态中意识水平的有前途的量度。这种关系是否适用于通过功能性脑成像获得的内在网络尚未得到检验。为了填补这一知识空白，我们从有意识的镇静和无意识麻醉的大鼠的功能磁共振图像（fMRI）的大规模动态分析中估计了LZC。从30分钟的全脑静息状态扫描中获得血氧依赖性（BOLD）信号，同时以20 mg / kg / h（有意识地镇静）和40 mg / kg / h的恒定输注速率静脉内注射麻醉性异丙酚无意识）。通过对BOLD信号的区域同质性（ReHo）进行滑动窗口分析，在体素水平上定义了动态脑网络。从低至高剂量的异丙酚进行扫描后，LZC显着降低了110％。结果表明，在大鼠中，有意识的镇静和麻醉的无意识受试者之间的LZC差异是保守的，并且在从fMRI获得的大规模脑网络中可以检测到这种效果。
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