Department of Clinical Neurosciences, University Hospital and University of Geneva, 1211 Geneva, Switzerland,
Department of Radiology and Medical Informatics, University of Geneva, 1205 Geneva, Switzerland, and.
J Neurosci. 2018 Jan 17;38(3):755-764. doi: 10.1523/JNEUROSCI.0831-17.2017. Epub 2017 Nov 22.
Ongoing neural dynamics comprise both frequency-specific oscillations and broadband-features, such as long-range dependence (LRD). Despite both being behaviorally relevant, little is known about their potential interactions. In humans, 8-12 Hz α oscillations constitute the strongest deviation from 1/f power-law scaling, the signature of LRD. We postulated that α oscillations, believed to exert active inhibitory gating, downmodulate the temporal width of LRD in slower ongoing brain activity. In two independent "resting-state" datasets (electroencephalography surface recordings and magnetoencephalography source reconstructions), both across space and dynamically over time, power of α activity covaried with the power slope <5 Hz (i.e., greater α activity shortened LRD). Causality of α activity dynamics was implied by its temporal precedence over changes of slope. A model where power-law fluctuations of the α envelope inhibit baseline activity closely replicated our results. Thus, α oscillations may provide an active control mechanism to adaptively regulate LRD of brain activity at slow temporal scales, thereby shaping internal states and cognitive processes. The two prominent features of ongoing brain activity are oscillations and temporal long-range dependence. Both shape behavioral performance, but little is known about their interaction. Here, we demonstrate such an interaction in EEG and MEG recordings of task-free human brain activity. Specifically, we show that spontaneous dynamics in alpha activity explain ensuing variations of dependence in the low and ultra-low-frequency range. In modeling, two features of alpha oscillations are critical to account for the observed effects on long-range dependence, scale-free properties of alpha oscillations themselves, and a modulation of baseline levels, presumably inhibitory. Both these properties have been observed empirically, and our study hence establishes alpha oscillations as a regulatory mechanism governing long-range dependence or "memory" in slow ongoing brain activity.
持续的神经动力学包括频率特异性振荡和宽带特征，如长程相关性（LRD）。尽管两者都与行为相关，但对它们的潜在相互作用知之甚少。在人类中，8-12 Hz 的α振荡构成了最强的偏离 1/f 幂律标度的偏差，是 LRD 的特征。我们假设，α振荡被认为施加主动抑制门控，降低较慢的持续脑活动中 LRD 的时间宽度。在两个独立的“静息状态”数据集（脑电图表面记录和脑磁图源重建）中，无论是跨越空间还是随时间动态，α活动的功率与功率斜率<5 Hz （即，更大的α活动缩短了 LRD）相关。α活动动力学的因果关系暗示了其在斜率变化之前的时间优先性。一个模型表明，α 包络的幂律波动抑制基线活动，这与我们的结果非常吻合。因此，α振荡可能为自适应调节较慢时间尺度上的大脑活动的 LRD 提供一种主动控制机制，从而塑造内部状态和认知过程。持续大脑活动的两个突出特征是振荡和时间长程相关性。两者都塑造了行为表现，但对它们的相互作用知之甚少。在这里，我们在任务自由的人类大脑活动的 EEG 和 MEG 记录中证明了这种相互作用。具体来说，我们表明，自发的α活动动力学解释了随后在低频和超低频率范围内的相关性变化。在建模中，α 振荡的两个特征对于解释对长程相关性的观察到的影响至关重要，即α 振荡本身的无标度特性，以及基线水平的调制，可能是抑制性的。这两个特性都已在经验上得到观察，因此我们的研究确立了α振荡作为调节缓慢持续脑活动中的长程相关性或“记忆”的机制。
