Human Research and Engineering Directorate, US DEVCOM Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA; Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA.
Human Research and Engineering Directorate, US DEVCOM Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA.
Neuroimage. 2021 Nov 1;241:118425. doi: 10.1016/j.neuroimage.2021.118425. Epub 2021 Jul 23.
Cascading high-amplitude bursts in neural activity, termed avalanches, are thought to provide insight into the complex spatially distributed interactions in neural systems. In human neuroimaging, for example, avalanches occurring during resting-state show scale-invariant dynamics, supporting the hypothesis that the brain operates near a critical point that enables long range spatial communication. In fact, it has been suggested that such scale-invariant dynamics, characterized by a power-law distribution in these avalanches, are universal in neural systems and emerge through a common mechanism. While the analysis of avalanches and subsequent criticality is increasingly seen as a framework for using complex systems theory to understand brain function, it is unclear how the framework would account for the omnipresent cognitive variability, whether across individuals or tasks. To address this, we analyzed avalanches in the EEG activity of healthy humans during rest as well as two distinct task conditions that varied in cognitive demands and produced behavioral measures unique to each individual. In both rest and task conditions we observed that avalanche dynamics demonstrate scale-invariant characteristics, but differ in their specific features, demonstrating individual variability. Using a new metric we call normalized engagement, which estimates the likelihood for a brain region to produce high-amplitude bursts, we also investigated regional features of avalanche dynamics. Normalized engagement showed not only the expected individual and task dependent variability, but also scale-specificity that correlated with individual behavior. Our results suggest that the study of avalanches in human brain activity provides a tool to assess cognitive variability. Our findings expand our understanding of avalanche features and are supportive of the emerging theoretical idea that the dynamics of an active human brain operate close to a critical-like region and not a singular critical-state.
级联的高振幅神经活动爆发，称为雪崩，被认为提供了对神经系统中复杂的空间分布相互作用的深入了解。例如，在人类神经影像学中，静息状态下发生的雪崩表现出具有标度不变性的动力学，支持大脑在接近临界点的假设，使长程空间通讯成为可能。事实上，有人提出，这种具有标度不变性的动力学，其特征是这些雪崩中的幂律分布，是神经系统中普遍存在的，并通过共同的机制出现。虽然对雪崩和随后的临界性的分析越来越被视为使用复杂系统理论来理解大脑功能的框架，但尚不清楚该框架将如何解释无处不在的认知变异性，无论是个体之间还是任务之间。为了解决这个问题，我们分析了健康人类在休息时的 EEG 活动中的雪崩，以及两种不同的认知需求不同的任务条件，这些任务条件产生了每个个体特有的行为测量。在休息和任务条件下，我们都观察到雪崩动力学表现出具有标度不变性的特征，但在其特定特征上有所不同，表现出个体的可变性。使用我们称为归一化参与度的新指标，该指标估计大脑区域产生高振幅爆发的可能性，我们还研究了雪崩动力学的区域特征。归一化参与度不仅显示了预期的个体和任务依赖性的变异性，而且还显示了与个体行为相关的特定于标度的变异性。我们的结果表明，研究人类大脑活动中的雪崩为评估认知变异性提供了一种工具。我们的发现扩展了我们对雪崩特征的理解，并支持了一个新兴的理论观点，即活跃的人类大脑的动力学接近类似临界的区域，而不是单一的临界状态。
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