BACKGROUND In the Wada test, one hemisphere is selectively anaesthetised by unilateral intracarotid injection of a fast-acting anaesthetic agent. This gives a unique opportunity to observe the functions and physiological activity of one hemisphere while anaesthetizing the other, allowing direct comparisons between brain states and hemispheres that are not possible in any other setting. AIM To test whether potential measures of consciousness would be affected by selective anesthesia of one hemisphere, and reliably distinguish the states of the anesthetized and non-anesthetized hemispheres. METHODS We analyzed EEG data from 7 patients undergoing Wada-tests in preparation for neurosurgery and computed several measures reported to correlate with the state of consciousness: power spectral density, functional connectivity, and measures of signal diversity. These measures were compared between conditions (normal rest vs unilateral anesthesia) and hemispheres (injected vs non-injected), and used with a support vector machine to classify the state and site of injection objectively from individual patient's recordings. RESULTS Although brain function, assessed behaviorally, appeared to be substantially altered only on the injected side, we found large bilateral changes in power spectral density for all frequency bands tested, and functional connectivity changed significantly both between and within both hemispheres. Surprisingly, we found no statistically significant differences in the measures of signal diversity between hemispheres or states, for the group of 7 patients, although 4 of the individual patients showed a significant decrease in signal diversity on the injected side. Nevertheless, including signal diversity measures improved the classification results, indicating that these measures carry at least some non-redundant information about the condition and injection site. We propose that several of these results may be explained by conduction of activity, via the corpus callosum, from the injected to the contralateral hemisphere and vice versa, without substantially affecting the function of the receiving hemisphere, thus reflecting what we call "cross-state unreceptiveness".

中文翻译：

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一侧半球麻醉时意识测量的变化（Wada 试验）

背景在Wada试验中，通过单侧颈动脉内注射速效麻醉剂选择性地麻醉一个半球。这提供了一个独特的机会，可以在麻醉另一个半球的同时观察一个半球的功能和生理活动，从而可以直接比较大脑状态和半球，这在任何其他环境中都是不可能的。目的测试意识的潜在测量是否会受到一个半球的选择性麻醉的影响，并可靠地区分麻醉和非麻醉半球的状态。方法 我们分析了 7 名接受 Wada 测试以准备神经外科手术的患者的脑电图数据，并计算了一些报告的与意识状态相关的测量值：功率谱密度、功能连接、和信号多样性的测量。这些措施在条件（正常休息与单侧麻醉）和半球（注射与非注射）之间进行了比较，并与支持向量机一起使用，从个体患者的记录中客观地对注射的状态和部位进行分类。结果 尽管从行为上评估的大脑功能似乎仅在注射侧发生了实质性改变，但我们发现所有测试频段的功率谱密度双边变化很大，并且功能连接在两个半球之间和内部都发生了显着变化。令人惊讶的是，对于 7 名患者，我们发现半球或状态之间的信号多样性测量没有统计学上的显着差异，尽管其中 4 名患者在注射侧的信号多样性显着降低。尽管如此，包括信号多样性措施改善了分类结果，表明这些措施至少携带一些关于条件和注射部位的非冗余信息。我们提出这些结果中的一些可以通过活动的传导来解释，通过胼胝体，从注射到对侧半球，反之亦然，而不会显着影响接收半球的功能，从而反映了我们所谓的“跨状态”不接受”。