Piastra Maria Carla, Oostenveld Robert, Homölle Simon, Han Biao, Chen Qi, Oostendorp Thom
Clinical Neurophysiology, Faculty of Science and Technology, Technical Medical Centre, University of Twente, Enschede, Netherlands.
Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, Netherlands.
Front Hum Neurosci. 2024 Feb 12;18:1279183. doi: 10.3389/fnhum.2024.1279183. eCollection 2024.
Volume conduction models of the human head are used in various neuroscience fields, such as for source reconstruction in EEG and MEG, and for modeling the effects of brain stimulation. Numerous studies have quantified the accuracy and sensitivity of volume conduction models by analyzing the effects of the geometrical and electrical features of the head model, the sensor model, the source model, and the numerical method. Most studies are based on simulations as it is hard to obtain sufficiently detailed measurements to compare to models. The recording of stereotactic EEG during electric stimulation mapping provides an opportunity for such empirical validation.
In the study presented here, we used the potential distribution of volume-conducted artifacts that are due to cortical stimulation to evaluate the accuracy of finite element method (FEM) volume conduction models. We adopted a widely used strategy for numerical comparison, i.e., we fixed the geometrical description of the head model and the mathematical method to perform simulations, and we gradually altered the head models, by increasing the level of detail of the conductivity profile. We compared the simulated potentials at different levels of refinement with the measured potentials in three epilepsy patients.
Our results show that increasing the level of detail of the volume conduction head model only marginally improves the accuracy of the simulated potentials when compared to sEEG measurements. The mismatch between measured and simulated potentials is, throughout all patients and models, maximally 40 microvolts (i.e., 10% relative error) in 80% of the stimulation-recording combination pairs and it is modulated by the distance between recording and stimulating electrodes.
Our study suggests that commonly used strategies used to validate volume conduction models based solely on simulations might give an overly optimistic idea about volume conduction model accuracy. We recommend more empirical validations to be performed to identify those factors in volume conduction models that have the highest impact on the accuracy of simulated potentials. We share the dataset to allow researchers to further investigate the mismatch between measurements and FEM models and to contribute to improving volume conduction models.
人体头部的容积传导模型被应用于多个神经科学领域，例如脑电图（EEG）和脑磁图（MEG）的源重建，以及脑刺激效果的建模。众多研究通过分析头部模型、传感器模型、源模型和数值方法的几何与电学特征的影响，对容积传导模型的准确性和敏感性进行了量化。由于难以获得足够详细的测量数据来与模型进行比较，大多数研究基于模拟。在电刺激映射期间记录立体定向脑电图为这种实证验证提供了机会。
在本文介绍的研究中，我们利用皮层刺激产生的容积传导伪迹的电位分布来评估有限元法（FEM）容积传导模型的准确性。我们采用了一种广泛使用的数值比较策略，即固定头部模型的几何描述和进行模拟的数学方法，并通过增加电导率剖面的细节水平来逐步改变头部模型。我们将不同细化水平下的模拟电位与三名癫痫患者的测量电位进行了比较。
我们的结果表明，与立体定向脑电图测量相比，增加容积传导头部模型的细节水平仅略微提高了模拟电位的准确性。在所有患者和模型中，测量电位与模拟电位之间的不匹配在80%的刺激 - 记录组合对中最大为40微伏（即10%的相对误差），并且它受记录电极和刺激电极之间距离的调节。
我们的研究表明，仅基于模拟来验证容积传导模型的常用策略可能会对容积传导模型的准确性给出过于乐观的看法。我们建议进行更多的实证验证，以确定容积传导模型中对模拟电位准确性影响最大的那些因素。我们共享数据集，以便研究人员能够进一步研究测量值与有限元模型之间的不匹配，并为改进容积传导模型做出贡献。
