Frohlich Joel, Irimia Andrei, Jeste Shafali S
Center for Autism Research and Treatment, University of California, Los Angeles, 760 Westwood Plaza, Semel Institute Suite 68-225, Los Angeles, CA, 90095, USA,
Brain Imaging Behav. 2015 Mar;9(1):5-18. doi: 10.1007/s11682-014-9339-3.
This work explores a feature of brain dynamics, metastability, by which transients are observed in functional brain data. Metastability is a balance between static (stable) and dynamic (unstable) tendencies in electrophysiological brain activity. Furthermore, metastability is a theoretical mechanism underlying the rapid synchronization of cell assemblies that serve as neural substrates for cognitive states, and it has been associated with cognitive flexibility. While much previous research has sought to characterize metastability in the adult human brain, few studies have examined metastability in early development, in part because of the challenges of acquiring adequate, noise free continuous data in young children. To accomplish this endeavor, we studied a new method for characterizing the stability of EEG frequency in early childhood, as inspired by prior approaches for describing cortical phase resets in the scalp EEG of healthy adults. Specifically, we quantified the variance of the rate of change of the signal phase (i.e., frequency) as a proxy for phase resets (signal instability), given that phase resets occur almost simultaneously across large portions of the scalp. We tested our method in a cohort of 39 preschool age children (age =53 ± 13.6 months). We found that our outcome variable of interest, frequency variance, was a promising marker of signal stability, as it increased with the number of phase resets in surrogate (artificial) signals. In our cohort of children, frequency variance decreased cross-sectionally with age (r = -0.47, p = 0.0028). EEG signal stability, as quantified by frequency variance, increases with age in preschool age children. Future studies will relate this biomarker with the development of executive function and cognitive flexibility in children, with the overarching goal of understanding metastability in atypical development.
这项研究探讨了脑动力学的一个特征——亚稳定性，通过它可以在功能性脑数据中观察到瞬态变化。亚稳定性是脑电生理活动中静态（稳定）和动态（不稳定）趋势之间的一种平衡。此外，亚稳定性是细胞集合快速同步的一种理论机制，这些细胞集合作为认知状态的神经基础，并且它与认知灵活性相关。虽然之前的许多研究都试图描述成人大脑中的亚稳定性，但很少有研究考察早期发育中的亚稳定性，部分原因是在幼儿中获取足够的、无噪声的连续数据存在挑战。为了完成这项工作，我们研究了一种表征幼儿期脑电图（EEG）频率稳定性的新方法，其灵感来自于之前描述健康成年人头皮脑电图中皮质相位重置的方法。具体来说，鉴于相位重置几乎同时发生在头皮的大部分区域，我们将信号相位（即频率）变化率的方差量化为相位重置（信号不稳定性）的指标。我们在39名学龄前儿童（年龄 = 53 ± 13.6个月）的队列中测试了我们的方法。我们发现，我们感兴趣的结果变量——频率方差，是信号稳定性的一个有前景的指标，因为它随着替代（人工）信号中相位重置的数量增加而增加。在我们的儿童队列中，频率方差随年龄呈横断面下降（r = -0.47，p = 0.0028）。通过频率方差量化的EEG信号稳定性在学龄前儿童中随年龄增加。未来的研究将把这个生物标志物与儿童执行功能和认知灵活性的发展联系起来，总体目标是了解非典型发育中的亚稳定性。
