He Mingjian, Liu Feng, Nummenmaa Aapo, Hämäläinen Matti, Dickerson Bradford C, Purdon Patrick L
Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States.
Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology (MIT), Cambridge, MA, United States.
Front Aging Neurosci. 2021 Feb 18;13:632310. doi: 10.3389/fnagi.2021.632310. eCollection 2021.
Electroencephalogram (EEG) power reductions in the aging brain have been described by numerous previous studies. However, the underlying mechanism for the observed brain signal power reduction remains unclear. One possible cause for reduced EEG signals in elderly subjects might be the increased distance from the primary neural electrical currents on the cortex to the scalp electrodes as the result of cortical atrophies. While brain shrinkage itself reflects age-related neurological changes, the effects of changes in the distribution of electrical conductivity are often not distinguished from altered neural activity when interpreting EEG power reductions. To address this ambiguity, we employed EEG forward models to investigate whether brain shrinkage is a major factor for the signal attenuation in the aging brain. We simulated brain shrinkage in spherical and realistic brain models and found that changes in the conductor geometry cannot fully account for the EEG power reductions even when the brain was shrunk to unrealistic sizes. Our results quantify the extent of power reductions from brain shrinkage and pave the way for more accurate inferences about deficient neural activity and circuit integrity based on EEG power reductions in the aging population.
此前众多研究均描述了衰老大脑中脑电图（EEG）功率降低的现象。然而，观察到的大脑信号功率降低的潜在机制仍不清楚。老年受试者EEG信号降低的一个可能原因可能是由于皮质萎缩，从皮质上的主要神经电流到头皮电极的距离增加。虽然脑萎缩本身反映了与年龄相关的神经变化，但在解释EEG功率降低时，电导率分布变化的影响往往与神经活动改变难以区分。为了解决这一模糊性问题，我们采用EEG正向模型来研究脑萎缩是否是衰老大脑信号衰减的主要因素。我们在球形和真实脑模型中模拟了脑萎缩，发现即使将大脑缩小到不切实际的大小，导体几何形状的变化也不能完全解释EEG功率的降低。我们的结果量化了脑萎缩导致的功率降低程度，并为基于老年人群EEG功率降低更准确地推断神经活动不足和电路完整性铺平了道路。
