Simultaneous head tissue conductivity and EEG source location estimation.
Simultaneous head tissue conductivity and EEG source location estimation.
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DOI：
10.1016/j.neuroimage.2015.08.032
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发表时间：
2016-01-01
期刊：
影响因子：
5.7
通讯作者：
Makeig S
中科院分区：
文献类型：
--
作者：
Akalin Acar Z;Acar CE;Makeig S
准确的脑电图 (EEG) 源定位需要一个包含主要头部组织的准确几何形状和电导率值的电头部模型。虽然头皮、大脑和脑脊液的电导率值一致，但测得的脑与颅骨电导率 (BSCR) 估计值在 8 到 80 之间变化，可能反映了受试者间和测量方法的差异。在模拟中，头骨电导率的错误估计可能会产生高达 3 厘米的源定位误差。在这里，我们描述了一种基于迭代梯度的同步组织电导率和源位置估计（SCALE）方法。 SCALE 使用的头皮投影图是通过对足够的高密度 EEG 数据进行充分的独立成分分析 (ICA) 分解而找到的近偶极有效 EEG 源获得的。我们将 SCALE 应用于基于 MR 图像的电头模型中 15 cm2 规模的皮质斑块源的模拟头皮投影，模拟 BSCR 为 30。以 80 或 20 的 BSCR 初始化，SCALE 估计 BSCR 为 32.6。在来自两个年轻人的（45 分钟，128 通道）EEG 数据的自适应混合 ICA (AMICA) 分解中，我们确定了 13 个独立组件的集合，这些组件具有与单个皮质源斑块兼容的近偶极头皮图。再次使用 BSCR 80 或 25 进行初始化，SCALE 分别为两个受试者提供了 34 和 54 的 BSCR 估计值。根据任何记录良好的脑电图数据，结合稳定且非侵入性采集的 MR 成像衍生电头模型，以非侵入性方式准确估计颅骨电导率的能力可以消除使用脑电图作为亚厘米级精确 3D 功能性皮层成像模式的关键障碍。
Accurate electroencephalographic (EEG) source localization requires an electrical head model incorporating accurate geometries and conductivity values for the major head tissues. While consistent conductivity values have been reported for scalp, brain, and cerebrospinal fluid, measured brain-to-skull conductivity ratio (BSCR) estimates have varied between 8 and 80, likely reflecting both inter-subject and measurement method differences. In simulations, mis-estimation of skull conductivity can produce source localization errors as large as 3 cm. Here, we describe an iterative gradient-based approach to Simultaneous tissue Conductivity And source Location Estimation (SCALE). The scalp projection maps used by SCALE are obtained from near-dipolar effective EEG sources found by adequate independent component analysis (ICA) decomposition of sufficient high-density EEG data. We applied SCALE to simulated scalp projections of 15 cm2-scale cortical patch sources in an MR image-based electrical head model with simulated BSCR of 30. Initialized either with a BSCR of 80 or 20, SCALE estimated BSCR as 32.6. In Adaptive Mixture ICA (AMICA) decompositions of (45-min, 128-channel) EEG data from two young adults we identified sets of 13 independent components having near-dipolar scalp maps compatible with a single cortical source patch. Again initialized with either BSCR 80 or 25, SCALE gave BSCR estimates of 34 and 54 for the two subjects respectively. The ability to accurately estimate skull conductivity non-invasively from any well-recorded EEG data in combination with a stable and non-invasively acquired MR imaging-derived electrical head model could remove a critical barrier to using EEG as a sub-cm2-scale accurate 3-D functional cortical imaging modality.