Optical Sciences Centre, Swinburne University of Technology, Hawthorn, Victoria, Australia.
Department of Physics and Astronomy, Swinburne University of Technology, Hawthorn, Victoria, Australia.
PLoS Comput Biol. 2020 Apr 30;16(4):e1007662. doi: 10.1371/journal.pcbi.1007662. eCollection 2020 Apr.
Alpha blocking, a phenomenon where the alpha rhythm is reduced by attention to a visual, auditory, tactile or cognitive stimulus, is one of the most prominent features of human electroencephalography (EEG) signals. Here we identify a simple physiological mechanism by which opening of the eyes causes attenuation of the alpha rhythm. We fit a neural population model to EEG spectra from 82 subjects, each showing a different degree of alpha blocking upon opening of their eyes. Though it has been notoriously difficult to estimate parameters by fitting such models, we show how, by regularizing the differences in parameter estimates between eyes-closed and eyes-open states, we can reduce the uncertainties in these differences without significantly compromising fit quality. From this emerges a parsimonious explanation for the spectral differences between states: Changes to just a single parameter, pei, corresponding to the strength of a tonic excitatory input to the inhibitory cortical population, are sufficient to explain the reduction in alpha rhythm upon opening of the eyes. We detect this by comparing the shift in each model parameter between eyes-closed and eyes-open states. Whereas changes in most parameters are weak or negligible and do not scale with the degree of alpha attenuation across subjects, the change in pei increases monotonically with the degree of alpha blocking observed. These results indicate that opening of the eyes reduces alpha activity by increasing external input to the inhibitory cortical population.
阿尔法阻断（alpha blocking），即在注意力集中于视觉、听觉、触觉或认知刺激时，阿尔法节律减少的现象，是人类脑电图（EEG）信号的最显著特征之一。在这里，我们确定了一种简单的生理机制，即眼睛睁开会导致阿尔法节律衰减。我们拟合了 82 位受试者的 EEG 频谱的神经群体模型，每位受试者在睁开眼睛时都表现出不同程度的阿尔法阻断。尽管通过拟合此类模型来估计参数一直是一个难题，但我们展示了如何通过正则化眼睛闭合和睁开状态之间的参数估计差异，在不显著影响拟合质量的情况下，减少这些差异的不确定性。由此得出一个简单的解释，即状态之间的频谱差异：只需改变单个参数 pei，即可对应于对抑制性皮质群体的持续兴奋性输入的强度，足以解释眼睛睁开时阿尔法节律的减少。我们通过比较每个模型在眼睛闭合和眼睛睁开状态之间的参数变化来检测到这一点。虽然大多数参数的变化较弱或可以忽略不计，并且与受试者之间的阿尔法衰减程度不成比例，但 pei 的变化随着观察到的阿尔法阻断程度单调增加。这些结果表明，眼睛睁开会通过增加对抑制性皮质群体的外部输入来减少阿尔法活动。
