[论文解读] No evidence that epilepsy impacts criticality in pre-seizure single-neuron activity of human cortex

Annika Hagemann, Jens Wilting+3 more|arXiv (Cornell University)|Apr 22, 2020

Neural dynamics and brain function被引用 5

一句话总结

本研究调查了癫痫是否会影响人类皮层单神经元活动中的临界性——即相变附近的动态稳定性。通过对20名癫痫患者记录数据应用一种新型无偏估计量，研究发现癫痫皮层在发作前并未更接近不稳定状态，也未表现出向不稳定的漂移；相反，发作前和无发作状态均保持在稳定且略微亚临界的动态区域，与健康哺乳动物皮层相似。

ABSTRACT

Epileptic seizures are characterized by abnormal and excessive neural activity, where cortical network dynamics seem to become unstable. However, most of the time, during seizure-free periods, cortex of epilepsy patients shows perfectly stable dynamics. This raises the question of how recurring instability can arise in the light of this stable default state. In this work, we examine two potential scenarios of seizure generation: (i) epileptic cortical areas might generally operate closer to instability, which would make epilepsy patients generally more susceptible to seizures, or (ii) epileptic cortical areas might drift systematically towards instability before seizure onset. We analyzed single-unit spike recordings from both the epileptogenic (focal) and the nonfocal cortical hemispheres of 20 epilepsy patients. We quantified the distance to instability in the framework of criticality, using a novel estimator, which enables an unbiased inference from a small set of recorded neurons. Surprisingly, we found no evidence for either scenario: Neither did focal areas generally operate closer to instability, nor were seizures preceded by a drift towards instability. In fact, our results from both pre-seizure and seizure-free intervals suggest that despite epilepsy, human cortex operates in the stable, slightly subcritical regime, just like cortex of other healthy mammalians.

研究动机与目标

• 确定癫痫皮层区域是否比非癫痫区域更接近不稳定状态（临界性）。
• 探究癫痫皮层在发作前的动态是否系统性地趋向不稳定。
• 评估癫痫患者在无发作间隔期间是否维持稳定的动态。
• 开发并应用一种从人类记录中少量神经元集合推断临界性的无偏估计量。

提出的方法

• 从20名癫痫患者的大脑局灶性（致痫性）和非局灶性皮层区域获取单个神经元动作电位记录。
• 应用一种新型无偏临界性距离估计量，从有限的神经元数据中推断动态区域。
• 利用临界性理论量化与不稳定性的距离，将亚临界区域作为稳定性的代理指标。
• 分析发作前和无发作间隔期，以比较时间与皮层区域之间的动态区域差异。
• 使用统计推断方法评估临界性偏离是否具有显著性或系统性。

实验结果

研究问题

• RQ1 癫痫皮层区域是否比非癫痫区域表现出更高的基线不稳定接近度？
• RQ2 癫痫皮层在发作前是否存在系统性地趋向不稳定的趋势？
• RQ3 癫痫患者在无发作间隔期间是否表现出与稳定性和亚临界性一致的动态区域？
• RQ4 能否从人类颅内记录中的小规模神经元集合可靠地估计临界性？

主要发现

• 在局灶性和非局灶性皮层区域之间，与不稳定性的距离无显著差异，表明癫痫组织并无普遍的不稳定性倾向。
• 在发作前期间未观察到系统性地趋向不稳定的趋势，表明癫痫发作并非源于网络动态的渐进性失稳。
• 发作前和无发作间隔期均一致地处于稳定且略微亚临界的动态区域，表明具有强大的动态稳定性。
• 新型估计量成功实现了从小规模神经元样本中无偏推断临界性，支持其在人类颅内记录中的应用。
• 结果表明，尽管存在反复发作，人类癫痫皮层仍维持着与健康哺乳动物新皮层相似的稳定动态区域。