[论文解读] Self-Organized Criticality Explains Readiness Potential

Katsushi Kagaya, Tomoyuki Kubota+1 more|arXiv (Cornell University)|Sep 19, 2022

Neural dynamics and brain function被引用 4

一句话总结

本文表明，螯虾运动神经元的树突活动表现出自组织临界性（SOC），其神经元爆发遵循大小和持续时间的幂律分布，并满足爆裂噪声关系。在自愿行为之前观察到的准备电位，源自这些无标度的爆发，表明SOC可能是从无脊椎动物到人类的自愿行为的普遍机制。

ABSTRACT

Readiness potential is a widely observed brain activity in several species including crayfish before the spontaneous behavioral initiation. However, it is poorly understood how this spontaneous activity is generated. The hypothesis that some specific, dedicated site is responsible for the spontaneity has been questioned. Here, by using intracellular recording and staining of the brain neurons in crayfish and modeling using the sandpile, which is the original model of self-organized criticality (SOC), we show that readiness potential can emerge everywhere in the brain because it is a SOC system. Despite the diversity in neurons and their morphology, brain neurons showed signatures of criticality and readiness potential. We find that the previously known readiness potential in a neuron is a consequence of the critical behavior of the entire network. Indeed, seemingly unrelated membrane potential activity in neurons in different animals can shape readiness potential when its time series are averaged after their alignment with respect to the spontaneous behavioral initiation. We show that the sandpile model not made for the potential, can form the premovement buildup activity similar to readiness potential. Scaling properties of the synaptic avalanches are in line with those of vertebrate species; thus, not only is the critical brain hypothesis supported in crayfish, but our findings might also provide a unified view of the basis of spontaneity in animal behavior.

研究动机与目标

• 调查螯虾运动神经元的树突神经活动是否表现出自组织临界性（SOC）的特征。
• 确定准备电位——一种在多种动物中观察到的运动前脑信号——是否源于SOC动力学。
• 检验相同的临界动力学是否在同一个神经系统中同时支配自愿行为和反射性行为。
• 利用胞内记录，将临界脑假说扩展至单个神经元和无脊椎动物系统。
• 通过与脊椎动物的胞外数据及理论模型比较，确立SOC在神经动力学中的普遍性。

提出的方法

• 在螯虾自发、行为静默状态下，对已识别的准备电位神经元进行胞内记录。
• 基于突触总和的大小和持续时间，通过阈值法和去趋势化处理，定义树突神经元爆发。
• 对爆发大小和持续时间的分布进行幂律拟合，以检验无标度性。
• 评估爆裂噪声关系：(τ−1)/(α−1) = γ，其中α和τ分别为大小和持续时间的幂律指数，γ为谱指数。
• 通过初始条件的鲁棒性及树突形态的自然变异，评估自组织性。
• 将标度函数和指数与BTW沙堆模型、准备电位的随机游走理论模型以及脊椎动物神经元爆发数据进行比较。

实验结果

研究问题

• RQ1 螯虾运动神经元的树突活动是否表现出幂律分布的爆发，这是自组织临界性的特征？
• RQ2 螯虾的准备电位是否由无标度的神经元爆发塑造，而非由确定性触发机制引起？
• RQ3 螯虾的自愿行走回路和反射性逃逸回路是否均表现出相同的临界标度行为？
• RQ4 能否利用胞内数据，将临界脑假说的普遍性扩展至无脊椎动物的单个神经元？
• RQ5 准备电位的出现是否直接源于SOC动力学，而无需精细调节的参数？

主要发现

• 螯虾准备电位神经元的树突神经元爆发在大小和持续时间上均遵循幂律分布，其指数与临界性一致。
• 爆裂噪声关系(τ−1)/(α−1) = γ得到满足，证实了在多个个体中均存在无标度动力学。
• 尽管树突形态存在自然变异，爆发形状的标度函数在不同螯虾个体间具有普适性。
• 在自愿行走回路和反射性逃逸回路中均观察到相同的临界动力学，表明存在共享的底层机制。
• 准备电位自发地从SOC动力学中产生，无需单一触发神经元或外部刺激。
• 研究结果支持自组织临界性作为从动物系统发育树中所有物种的自愿行为默认神经机制的普遍性。