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首页> 美国卫生研究院文献>PLoS Clinical Trials >When Is the Brain Dead? Living-Like Electrophysiological Responses and Photon Emissions from Applications of Neurotransmitters in Fixed Post-Mortem Human Brains
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When Is the Brain Dead? Living-Like Electrophysiological Responses and Photon Emissions from Applications of Neurotransmitters in Fixed Post-Mortem Human Brains

机译：什么时候脑死了？在固定的晚期人体后脑中应用神经递质的类似活体的电生理反应和光子发射。

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The structure of the post-mortem human brain can be preserved by immersing the organ within a fixative solution. Once the brain is perfused, cellular and histological features are maintained over extended periods of time. However, functions of the human brain are not assumed to be preserved beyond death and subsequent chemical fixation. Here we present a series of experiments which, together, refute this assumption. Instead, we suggest that chemical preservation of brain structure results in some retained functional capacity. Patterns similar to the living condition were elicited by chemical and electrical probes within coronal and sagittal sections of human temporal lobe structures that had been maintained in ethanol-formalin-acetic acid. This was inferred by a reliable modulation of frequency-dependent microvolt fluctuations. These weak microvolt fluctuations were enhanced by receptor-specific agonists and their precursors (i.e., nicotine, 5-HTP, and L-glutamic acid) as well as attenuated by receptor-antagonists (i.e., ketamine). Surface injections of 10 nM nicotine enhanced theta power within the right parahippocampal gyrus without any effect upon the ipsilateral hippocampus. Glutamate-induced high-frequency power densities within the left parahippocampal gyrus were correlated with increased photon counts over the surface of the tissue. Heschl’s gyrus, a transverse convexity on which the primary auditory cortex is tonotopically represented, retained frequency-discrimination capacities in response to sweeps of weak (2μV) square-wave electrical pulses between 20 Hz and 20 kHz. Together, these results suggest that portions of the post-mortem human brain may retain latent capacities to respond with potential life-like and virtual properties.
机译：可以通过将器官浸入固定液中来保存人体后尸体的结构。一旦大脑被灌注，细胞和组织学特征将在较长的时间内保持不变。但是，不能认为人脑的功能会在死亡和随后的化学固定之后得以保留。在这里，我们提出了一系列实验，共同驳斥了这一假设。相反，我们建议化学保存大脑结构会导致一些保留的功能能力。通过在乙醇-福尔马林-乙酸中维持的人类颞叶结构的冠状和矢状断面内的化学和电探针引发了与生活条件相似的模式。这是通过可靠调制频率相关的微伏波动来推断的。这些微弱的微伏波动通过受体特异性激动剂及其前体（即烟碱，5-HTP和L-谷氨酸）增强，并被受体拮抗剂（即氯胺酮）减弱。 10 nM尼古丁的表面注射增强了右海马旁回旋内的theta功能，而对同侧海马没有任何影响。谷氨酸在左海马旁回中诱导的高频功率密度与组织表面上增加的光子计数相关。 Heschl的回波（在其上以听觉方式表示主要听觉皮层的横向凸面）保留了频率区分能力，以响应20 Hz至20 kHz之间的弱（2μV）方波电脉冲的扫描。综合起来，这些结果表明，事后人类大脑的某些部分可能保留潜在的能力，以潜在的逼真的和虚拟的属性做出响应。

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